Bolt assembly crud

[acaixguard]

I notice after cleaning my bolt assembly, the back part of it (where it curves outward toward the rings) has a layer of hardened carbon that just won't come out. I didn't try scraping it away, but using a soft brush doesn't seem to get it out.
Is this buildup normal? Is it important to eventually get rid of this layer of black residue?
Thanks in advance!

[Javelinadave]

I soak it is Hoppes for a while and then scrub it with a brass brush.

[polymorpheous]

It's completely normal.
It won't affect function.

[KrampusArms]

Yes it is normal. Scrape at it with a spent casing after soaking with CLP. Also, a bit of preventative maintenance, oil the bolt liberally before & after you shoot.

It doesnt really affect anything IMO anyways.

I'm going to guess youre new to the AR scene judging from your pivot pin detent removal thread as well.

Additionally (orange search)

[IYAAYASwarrior]

It is a normal issue. If you feel the need to get rid of it just soak it in some solvent and use a wire brush to get it off.

[Markasaurus]

Everybody basically says leave it alone. I can't.not only does it bother me to have a still-dirty gun, the metal underneath will pitt if you ignore the carbon long enough.
I clean my bolt tail. The crt~15 tool is what you want. Everybody sells it for $40 and nobody has it cheaper. I use the G and g tool, and the botach tactical tool plus scotch BRITE pads. I have tried every chemical there is-clp, acetone, carbon cutter, m~pro 7. Don't waste your time only the tools work. It takes me 10 minutes to get that bolt tail clean as new. I forgot to mention i bought a chrome plated bolt from stag for $55. Which helps a little but not really $55 worth of help.

Is it worthwhile to clean the bolt tail like new, to me it is! Truth be told most of the people who say don't bother are probably right

[NeoNeanderthal]

Sounds like ocd to me.

[NeoNeanderthal]

Everyone is suggesting you use the search button (for this thread and your cam pin one).

But you should really watch a few instructional dvd's and sign up for a course. Both the Magpul Carbine I and Vickers Carbine DVD's have a section on disassembly and cleaning.

It is hard to explain via typing how to do physical tasks. Video is a much better medium for this sort of thing. The videos wont really make you a better shooter but will give you some idea of how the platform operates before you take a course.

The biggest issue I see (and i had this issue to when i started shooting) is that people think less lube is better. This is partially the millitary's fault as they have preached cleanliness over keeping the gun wet. 99% of shooters think they should clean their gun after they shoot it everytime. And most people think too much lube causes issues. I could take a whole bottle of mobile 1 engine oil and dump it into and onto my gun and it would run better then if i ran it dry. I believe watching pros apply oil (how much and where) is worth the price of one of these dvd's to a new shooter.

This is the Magpul disassembly and cleaning portion to give you an idea of what im talking about.
http://www.youtube.com/watch?v=eG92bvksfcA

Hope this helps

[acaixguard]

Thanks for the replies.
I'm not completely new to the AR platform, as I've owned one for over 10 years. But I was never that into it until recently. Just not sure what an acceptable level of buildup is.
I actually do have the Vickers carbine video, and I clean my rifle to the extent he shows (maybe a bit more detailed).
I definitely lube the hell out of the BCG though. Most parts of the receiver, I keep just very lightly lubed.

[lifebreath]

CLP and 3M Scotch Brite pad.

[sinlessorrow]

The proper way to clean the AR-15 bolt and carrier is with a rag.

If you cannot remove the carbon with a rag then its un important. The AR-15 is self scraping and self limiting in where carbon builds up.

Also pat rogers proved that carbon does not pitt anything.

[GTifosi]

I recently stumbled over a blip somewhere that said that using a metal brush could be sort of a bad idea when cleaning the bolt tail, though not because it was ineffective, but in that it stood a higher chance of catching and deforming a ring and/or having bristles come loose and get trapped under the gas rings where they could create binding issues.

Just getting that out there as a point of possible interest, not an effort to try and change the world or freak people out.
Purely informational to be considered, implimented or ignored at your own discretion.

[Littlelebowski]

Yes it is normal. Scrape at it with a spent casing after soaking with CLP. Also, a bit of preventative maintenance, oil the bolt liberally before & after you shoot.

It doesnt really affect anything IMO anyways.

I'm going to guess youre new to the AR scene judging from your pivot pin detent removal thread as well.

Additionally (orange search)
No need to scrape it. Lube, ignore, drive on.

[Tweak]

I learned to never say never and knock down the carbon occasionally. Nothing fanatical.

Had a guy's (traveling instructor type) rifle malfunction at a class (Ayoob I think), repeated Failures to Lock. Pulled the BCG and the bolt wouldn't move fully into the locked position. Pulled the bolt and all was well except for the accumulation of carbon on the bolt tail and inside the carrier. Knocked those down and the bolt fully telescoped.

Lube and powder choices contribute greatly to this.

An extreme case but still a data point.

[Kodiak]

Probably not the right way, I use a pocket knife to scrape it off and lube it.

[Quiet-Matt]

I soak it then slip a spent .45acp casing over the bolt tail and scrape it off that way. Any left over gets the bronze brush treatment.

[Iraqgunz]

More people cause damage to their weapons finish by using green pads and other such nonsense than if they had left it alone.


CLP and 3M Scotch Brite pad.

[Littlelebowski]

Wow, it's like people never read this site or take classes.

[Col_Crocs]

More people cause damage to their weapons finish by using green pads and other such nonsense than if they had left it alone.

So true. This is one of those things that do more harm than. Im not against scraping but it should not be done regularly.The carbon on the tail is self limiting. Once a year maybe when doing a thorough cleaning and it helps to use a good solvent to ease the scraping. Ive found froglube on a hot bolt really eases the task.

[militarymoron]

The carbon on the tail is self limiting.
okay, i've heard this so many times before i'm wondering by what mechanism the carbon 'self limits'?
does it build up to a certain point then not build up anymore? where does the subsequent carbon go after the previous carbon has self limited? does it build up then fall off? does it somehow lose adhesion to the bolt when it reaches a certain thickness?
just asking, as i'm curious.

[tommyrott]

i think the self limiting device is that when the gun quits running you clean it thouroughly :lol:

[sinlessorrow]

okay, i've heard this so many times before i'm wondering by what mechanism the carbon 'self limits'?
does it build up to a certain point then not build up anymore? where does the subsequent carbon go after the previous carbon has self limited? does it build up then fall off? does it somehow lose adhesion to the bolt when it reaches a certain thickness?
just asking, as i'm curious.

I think its more like, by the time it builds up to a point that it actually matters the bolt will probably have sheared a few lugs.

[Littlelebowski]

i think the self limiting device is that when the gun quits running you clean it thouroughly :lol:

Just add lube.

[TheBelly]

No need to scrape it. Lube, ignore, drive on.

I've said this about many things lately. This is easily the advice about keeping an AR running.

[yhmspecter]

Just add lube.
More soild advise, so many AR owners are to worried about how clean they get the rifle..Between all the guys here with experience using the weapon system, and the extremely well documented, and rarely cleaned rifle collection EAG tactical runs you'd think that it would be understood that the rifle doesnt need OCD attention to detail type cleaning..A quick wipe down, and more lube is the answer to AR cleaning

[Tweak]

i'm wondering by what mechanism the carbon 'self limits'?

Why, by the same mechanism seen in the M1, M14 and M60, FM.

[militarymoron]

Why, by the same mechanism seen in the M1, M14 and M60, FM.

when they quit workin'?

[sinlessorrow]

when they quit workin'?

Lol pretty much, but going by pat rogers filthy 14 you will break a bolt before carbon buildup is an issue

[jonconsiglio]

Leave it there, you will never build up enough to alter function in any way, whatsoever.

What is happening here lately with some of these responses…?

[polymorpheous]

What is happening here lately with some of these responses…?

I agree.
A lot of new members handing out bad advise.

[Markasaurus]

I recently stumbled over a blip somewhere that said that using a metal brush could be sort of a bad idea when cleaning the bolt tail, though not because it was ineffective, but in that it stood a higher chance of catching and deforming a ring and/or having bristles come loose and get trapped under the gas rings where they could create binding issues.

Just getting that out there as a point of possible interest, not an effort to try and change the world or freak people out.
Purely informational to be considered, implimented or ignored at your own discretion.

That, plus using a wire brush on bolt tail carbon doesn't work. If you want to remove the carbon you have to scrape it off, period.

[militarymoron]

Leave it there, you will never build up enough to alter function in any way, whatsoever.

What is happening here lately with some of these responses…?

i decided to respond because i'd like to get to the bottom of it. the main reason that the 'anti-cleaners' give is that by scraping the carbon off the bolt tail, you risk damaging it, and that it's a 'critical dimension'.
however, the built up crud on the tail changes the dimensions much more than any cosmetic damage or worn finish that using a bolt scraper tool does. so, that argument contradicts itself.
so, is it critical or not? personally, i don't think so. i don't think that scraping carbon off the bolt tail with the proper tool can damage or remove metal from the bolt enough to affect the functioning of the weapon. if so, letting the crud build up would affect it more. is it necessary to scrape it off? i don't think so either.

IMHO, i just think that it boils down to personal preference. clean it if you want or don't (and keep it lubed well). either way seems to work for both parties or else there wouldn't be much to argue about.

[Arctic1]

I use a copper or bronze brush to remove carbon build up on the piston on my gun.

As long as the metal on the scraping tool/brush etc is "softer" than the object being scraped, it should not damage it. I'm no metallurgist, but that's how it was explained to me.

And I would think that it is the rings that are critical, as they form the seal in the carrier body, not the tail.

And I see someone referring to Pat Rogers in regards to cleaning. Now, I'm not pretending to speak for Pat, as I most certainly do not, but in his video Basic Carbine from Panteao Productions he states very clearly his take on weapons cleaning. He does not clean his guns at all, because he does not carry one for a living anymore. He also states that if he carried a gun for a living, he would certainly clean it on a regular basis.

[sinlessorrow]

I use a copper or bronze brush to remove carbon build up on the piston on my gun.

As long as the metal on the scraping tool/brush etc is "softer" than the object being scraped, it should not damage it. I'm no metallurgist, but that's how it was explained to me.

And I would think that it is the rings that are critical, as they form the seal in the carrier body, not the tail.

And I see someone referring to Pat Rogers in regards to cleaning. Now, I'm not pretending to speak for Pat, as I most certainly do not, but in his video Basic Carbine from Panteao Productions he states very clearly his take on weapons cleaning. He does not clean his guns at all, because he does not carry one for a living anymore. He also states that if he carried a gun for a living, he would certainly clean it on a regular basis.

Of course, but I used it as an example of how 20,000 rounds worth of carbon on the bolt tail had no adverse effects.

I clean my rifles after every time theyre used but it only consists of wiping down everything and running a bore snake down the bore.

Carbon build has no advers effects on the rifle, which is why scraping is not needed.

Someone on here posted their LMT with 10,000 rounds and no cleaning and he lived in the desert i believe so it was full of sand and lubrication was all that was needed.

If your rifle is your duty rifle it should be cleaned but not like alot seem to think. My friends always insist my rifle will fail because I dont scrape my rifle clean and they try to give me pointers like using sectional rods to clean the chrome plated bolt carrier chamber(take 4 and twist.....), or using a M9(bayonet) to clean the bolt tail because this is what they are taught in the Army....that carbon is what makes your rifle have stoppages.....

[Arctic1]

I don't disagree about the carbon build up issue. I just have my routine for maintenance, and specific reason why I do it and enforce that standard with my guys.

Here is something I posted on a different site:


A little anecdote to perhaps explain why I have my guys follow a strict maintenance regime:

One unit in the norwegian military absolutely hates the HK416. They hate it because they experienced several malfunctions during a very heavy TIC in Afghanistan, the most prevalent was short stroking, or failure to cycle. They took casualties during the TIC, with two cat A patients who barely made it.

During the investigation, by a commission sent down to identify lessons learned, members of this unit suggested that the HK416 is not suited for combat and that they now had zero trust in the weapon. The chief of the Army was tasked with identifying wether or not the Army should continue using the HK416, or if the Army should lead a service wide initiative to replace it all together.

Now, it of course never came to that, as there are several other units who absolutely love the gun. We are in fact purchasing new weapons. Still, what was discovered during the investigation was that the unit in question had very lax maintenance standards, a factor that greatly contributed to the malfunctions they experienced that day. The guns had never been cleaned, and had insufficient amounts of lube.

This incident happened after I came home from Afghanistan, so it did not influence the standard I follow. It did, however, reinforce my belief that the user must do every step neccessary to ensure reliable function when he rolls out of the gate.

We perform field maintenance every time we bivouac for the night, either on operations or on exercise. We call it TEXAS, and it is part of our daily maintenance routine:

TEXAS (Personal and crew served/vehicle mounted weapons)
SIBERIA (Personell)
LAS VEGAS (Optics/NV/Comms)
DETROIT (Vehicles)

The weapon is stripped down to main components, all foreign debris and moisture is removed, and the weapon is lubed. It might be viewed as unneccessary by some, but this is the best way for the SL to be sure of the status of his squads equipment, for the PL to be sure of the his platoons equipment and so forth. Nobody has a chance to be 'that guy' who didn't lube his gun, or the like.

And that has happened. During HOTO with our replacement team, I gave my replacement a few tips on the RWS I had manned during my tour. I told him that it NEEDS lube! As we were rolling out to one of the FOB's, we stopped by some hills so the new guys could get a chance to test fire their guns in country. As the shooting went on, I could hear my replacment on comms stating that he had some malfunctions with the gun. I just shook my head in disbelief. When we arrived at the FOB I asked him if he had lubed the gun; he replied that he hadn't, because he wanted to test how it ran without lube.:rolleyes:

This was not in Norway on some square range, mind you, but in Taliban country.....I was less than impressed.

So this is why I do not subscribe to the less is more approach to cleaning, although I completely understand that the gun can accept a lot of soot without suffering a malfunction.

[sinlessorrow]

I don't disagree about the carbon build up issue. I just have my routine for maintenance, and specific reason why I do it and enforce that standard with my guys.

Here is something I posted on a different site:

Excellent post Artic and very, very good information.

Listening to my friends bad mouth their M4's I can honestly say the issues yall experienced are what my friends experienced.

Its always easier to lay the blame on the rifle than the user.

If you honestly want to scrape carbon the only tool i would recommend is the CAT-M4. It still makes me cringe to see scraping and I have done it before myself, but the CAT-M4 does the least damage IMO.

Just read your edit Arctic.

I do see your point, i think when in your position and having non gun guys you have to take extra steps, cause common sense isnt so common after all.

The main thing I advise against is scraping with tools not designed for that. My bestfriends have told me things they have done to pass inspection, including brillow pads, sectional rods, M9 bayonets, shaving cream, etc. That is all about getting every spot of carbon off, something that is not needed.

The carbon on the bolt tail and inside the carrier on he M4 should never ever be so bad that it requires scraping by incorrect methods.

[jonconsiglio]

i decided to respond because i'd like to get to the bottom of it. the main reason that the 'anti-cleaners' give is that by scraping the carbon off the bolt tail, you risk damaging it, and that it's a 'critical dimension'.
however, the built up crud on the tail changes the dimensions much more than any cosmetic damage or worn finish that using a bolt scraper tool does. so, that argument contradicts itself.
so, is it critical or not? personally, i don't think so. i don't think that scraping carbon off the bolt tail with the proper tool can damage or remove metal from the bolt enough to affect the functioning of the weapon. if so, letting the crud build up would affect it more. is it necessary to scrape it off? i don't think so either.

IMHO, i just think that it boils down to personal preference. clean it if you want or don't (and keep it lubed well). either way seems to work for both parties or else there wouldn't be much to argue about.

I agree with what you are saying. I guess my reply was a little more broad than just this thread.

I guess I'm not really in either of those two camps as I just thinks it's a waste of time, not that it will do any serious damage. I don't think leaving it will hurt a thing and I don't think cleaning really will either, though I will not spend time cleaning something unless there's a benefit.

I have one rifle I keep pretty clean, within reason, as it has a more important role than the others. The others get cleaned if they're contaminating stuff around them.

[CatBacker88]

Of course, but I used it as an example of how 20,000 rounds worth of carbon on the bolt tail had no adverse effects.

I clean my rifles after every time theyre used but it only consists of wiping down everything and running a bore snake down the bore.

Carbon build has no advers effects on the rifle, which is why scraping is not needed.

Someone on here posted their LMT with 10,000 rounds and no cleaning and he lived in the desert i believe so it was full of sand and lubrication was all that was needed.

If your rifle is your duty rifle it should be cleaned but not like alot seem to think. My friends always insist my rifle will fail because I dont scrape my rifle clean and they try to give me pointers like using sectional rods to clean the chrome plated bolt carrier chamber(take 4 and twist.....), or using a M9(bayonet) to clean the bolt tail because this is what they are taught in the Army....that carbon is what makes your rifle have stoppages.....

Having spent just shy of 23 years in the Army (Field Artillery) I will quickly break my usual silence to reinforce the suggestion that what folks learned in the Army about small (and big) arms maintenance is often based more on preparation for home station inspections than for combat. I hope that we've outgrown such stupidity. Looking back on my Cold War years gives me shivers to think about how much we might have lost in a throwdown with the Soviets after forgetting all the lessons learned about the M16A1 and the M2 and M60 machineguns after Vietnam and before OIF and OEF. We re-learned a little during the relatively short scraps at Grenada and Panama and Desert Storm, but those were drive-by shootings compared to what we've done and hopefully learned since 2003. Our Army spent a long time with way too many commanders, first sergeants and command sergeants major who had never been in combat. Those people were the types who would go through a company/battery/troop arms room and pronounce the unit a disaster area because of carbon on bolt tails. Sergeant Majors were particularly notorious for that kind of behavior. One silver lining behind the dark cloud of all these years of firefights is that virtually all of our company and battalion and BCT commanders (at least in combat arms units) and their senior enlisted men have actually been in close combat or close enough to it to have their priorities straight.

[MarkG]

Leave it there, you will never build up enough to alter function in any way, whatsoever.

The terminus of the gas system (the chamber formed by the bolt rings, carrier and bolt tail) is relatively small. Given the fact that chamber/bore pressure and gas transfer times are measured in milliseconds, is there any chance that reducing the volume of the terminus by 20% (arbitrary) will lead to accelerate wear caused the bolt unlocking prematurely?

or...

Was this a design consideration by Stoner or Colt (from a product improvement standpoint) and terminus volume was increased to allow for a reliable margin of operation given that a only a fixed amount of carbon built up?

[Arctic1]

Having spent just shy of 23 years in the Army (Field Artillery) I will quickly break my usual silence to reinforce the suggestion that what folks learned in the Army about small (and big) arms maintenance is often based more on preparation for home station inspections than for combat. I hope that we've outgrown such stupidity. Looking back on my Cold War years gives me shivers to think about how much we might have lost in a throwdown with the Soviets after forgetting all the lessons learned about the M16A1 and the M2 and M60 machineguns after Vietnam and before OIF and OEF. We re-learned a little during the relatively short scraps at Grenada and Panama and Desert Storm, but those were drive-by shootings compared to what we've done and hopefully learned since 2003. Our Army spent a long time with way too many commanders, first sergeants and command sergeants major who had never been in combat. Those people were the types who would go through a company/battery/troop arms room and pronounce the unit a disaster area because of carbon on bolt tails. Sergeant Majors were particularly notorious for that kind of behavior. One silver lining behind the dark cloud of all these years of firefights is that virtually all of our company and battalion and BCT commanders (at least in combat arms units) and their senior enlisted men have actually been in close combat or close enough to it to have their priorities straight.

I am sure the proponents of regular cleaning and maintenance do not advocate a white glove regime. I sure don't.

The point is, however, that to properly inspect weapons parts, the gun must be clean. Also, there is a lot more than just carbon build up or soot than can get into a weapons system, that can cause fouling or increase wear.

And lastly, PCC's and PCI's aren't only done pre-anything. It is a continous process, making sure the equipment is operational at all times. In my opinion, if you adopt an attitude that weapons do not need to be cleaned, only lubed, it will be more difficult to ensure that guys take care of their guns. Even though it is only lubing it.

Lastly, has anyone ever done a comparative study between two identical guns where one system is regularly cleaned and lubed, while the other is never cleaned, only lubed, to see if there is a noticeable difference in parts wear?

I have seen many stupid things, like attaching a cleaning rod with a chamber brush to an electrical drill, and cleaning the chamber using that combination, to people using steel wool, scraping parts with knives/screwdrivers etc.

There is a middle ground between white glove cleaning and stupid cleaning, whilst being more thorough than just adding lube.

[CatBacker88]

I am sure the proponents of regular cleaning and maintenance do not advocate a white glove regime. I sure don't.

The point is, however, that to properly inspect weapons parts, the gun must be clean. Also, there is a lot more than just carbon build up or soot than can get into a weapons system, that can cause fouling or increase wear.

And lastly, PCC's and PCI's aren't only done pre-anything. It is a continous process, making sure the equipment is operational at all times. In my opinion, if you adopt an attitude that weapons do not need to be cleaned, only lubed, it will be more difficult to ensure that guys take care of their guns. Even though it is only lubing it.

Lastly, has anyone ever done a comparative study between two identical guns where one system is regularly cleaned and lubed, while the other is never cleaned, only lubed, to see if there is a noticeable difference in parts wear?

I have seen many stupid things, like attaching a cleaning rod with a chamber brush to an electrical drill, and cleaning the chamber using that combination, to people using steel wool, scraping parts with knives/screwdrivers etc.

There is a middle ground between white glove cleaning and stupid cleaning, whilst being more thorough than just adding lube.

100% agreed; these are exactly the lessons I'm hoping we've learned. Lube is all well and good but sooner or later enough organic crap (sand and soil) will find its way into a weapon and do a lot more mischief than a bunch of carbon will. Let's not put too much faith in our lubricants.

[Redhat]

So if you were to write the new guidance on cleaning, what would you change?

I am in the camp of those who believe in proper cleaning and more importantly inspection. This conversation goes on and on but I haven't really heard how properly cleaning a weapon is bad or causes damage?

I will also throw out there that IMO, the issued CLP is less than satisfactory.

[jonconsiglio]

So if you were to write the new guidance on cleaning, what would you change?

I am in the camp of those who believe in proper cleaning and more importantly inspection. This conversation goes on and on but I haven't really heard how properly cleaning a weapon is bad or causes damage?

I think a work rifle should be maintained and lubed properly, but not white glove. I don't think it matters on a trainer or dirt shooter though and I wouldn't bother with much more than a wipe down of the internals now and then.

[Littlelebowski]

My time is money and I have better things to do rather than clean when I don't have to.

[Arctic1]

I will also throw out there that IMO, the issued CLP is less than satisfactory.

I have for the most part used BreakFree CLP, and personally I don't see what the big deal is. It has worked fine for me in a variety of environments (arctic, desert, subtemperate forest).

I have also used it on a variety of systems; G3, HK416, Glock 17, MG-3, FN-MAG, Minimi, Browning M2 HMG with no issues.

I have tried Slip2000 as well, and I can't say I have experienced a noticeable difference. Not that I have done tests to find out though.

[Redhat]

I have for the most part used BreakFree CLP, and personally I don't see what the big deal is. It has worked fine for me in a variety of environments (arctic, desert, subtemperate forest).

I have also used it on a variety of systems; G3, HK416, Glock 17, MG-3, FN-MAG, Minimi, Browning M2 HMG with no issues.

I have tried Slip2000 as well, and I can't say I have experienced a noticeable difference. Not that I have done tests to find out though.

The problem I have with it is not lubrication but its cleaning ability...or lack thereof. I believe a solvent does it quicker, easier and better.

[Arctic1]

Okay, now I'm tracking. I haven't used proper solvents for that, so that might well be.

The only solvent approved for use in our system is a copper fouling solvent for the Barrett M82 (not KG12).

ETA: It's this one:

http://www.morgansgunroom.com/acatalog/GMK_GU_93308.jpg

[sinlessorrow]

Ive never been in the military, but I have shot in some sandy places that caused my rifle to have plenty of sand at the end of the day.

My cleaning has and will always be to basically just wipe down the interior of the rifle with a rag, same for the bolt, wipe it down really good.

for the inside of the carrier I use the Cat-M4 with a 2"x2" patch on it and swab the inside of the carrier real good.

Then I run a bore snake 4 times through the bore.

For the chamber I use the chamber brush and twirl it for about 20 seconds and then dry out the chamber.

Finally I reassemble and Relube, this has always worked for me.

Arctic1, I doubt this applies to you since ya'll run the HK416, but from my experiences CLP has a very very low flash point. From what I have seen 6-7 mags of ammo and it will be mostly gone from the BCG. Slip2000EWL has lasted me 1,000 rounds in 1.5hrs before without needing to be relubed. I would have had to apply CLP 2-3 times during that time. CLP is also pretty hazardous to your health if you read the MSDS.

[everyusernametaken]

How does Gunzilla compare to Break Free CLP, in terms of staying put in the BCG when subjected to the heat of sustained fire? Is it basically equivalent? Any truth to the claims of being better than Break Free in sandy environments? Also, is the military actually using it like they claim?

[Roodoodog]

While on the subject and just out of curiosity, does anyone have any experiences with these yet?

C.A.T. M-4
http://i45.tinypic.com/sc4d4y.jpg

In regards to the original post, in my limited experience (but as posted by several others as well) I found keeping my bolt assembly lubed helped keep a majority of the carbon off and what did stick was easily removed.

[sinlessorrow]

While on the subject and just out of curiosity, does anyone have any experiences with these yet?

C.A.T. M-4
http://i45.tinypic.com/sc4d4y.jpg

In regards to the original post, in my limited experience (but as posted by several others as well) I found keeping my bolt assembly lubed helped keep a majority of the carbon off and what did stick was easily removed.

I have one and its the only scraper i would ever recommend, that said I dont use it to scrape, I use it to clean the inside of the carrier since it has a slot for a 2"x2" patch to get into the carrier and wipe it out.

the CAT-M4 does everything it says it does.

[Roodoodog]

I have one and its the only scraper i would ever recommend, that said I dont use it to scrape, I use it to clean the inside of the carrier since it has a slot for a 2"x2" patch to get into the carrier and wipe it out.

the CAT-M4 does everything it says it does.

Thanks Sin, for under $30 I should probably pony up the cash and grab one.

[Markasaurus]

i decided to respond because i'd like to get to the bottom of it. the main reason that the 'anti-cleaners' give is that by scraping the carbon off the bolt tail, you risk damaging it, and that it's a 'critical dimension'.
however, the built up crud on the tail changes the dimensions much more than any cosmetic damage or worn finish that using a bolt scraper tool does. so, that argument contradicts itself.
so, is it critical or not? personally, i don't think so. i don't think that scraping carbon off the bolt tail with the proper tool can damage or remove metal from the bolt enough to affect the functioning of the weapon. if so, letting the crud build up would affect it more. is it necessary to scrape it off? i don't think so either.

IMHO, i just think that it boils down to personal preference. clean it if you want or don't (and keep it lubed well). either way seems to work for both parties or else there wouldn't be much to argue about.

I use the G and G tool and the green scotch brite pads (the ones without the aluminum strands in them, from the 99 cents store). My bolt is a stag chrome plated, so if this treatment were damaging the metal i'd see it.

Here's the G & G tool, it is only $19.95. Half the cost of the CRT-15. You shove in the bolt tail, the round steel blade bears against the carbon. You then rotate the bolt, and the steel blade scrapes off the carbon. The steel blade is not very sharp at all, but it is contoured properly to fit the curve of the bolt tail. They sell spare blades but the one that comes with it is two sided, if you wear out one end there's another end to use. Also the G & G people sell what are basically scotch brite pads cut into strips, for final finishing. I just buy a 3 pack of the pads at the store and cut them into 2 inch wide strips, and it is the same thing.
http://i80.photobucket.com/albums/j169/marc780/BCFinal.jpg

Here's pictures of my chrome plated bolt after 1000 rounds, is there any chance i am damaging it?

http://i80.photobucket.com/albums/j169/marc780/Photobucket-AR_BOLT-007.jpg
http://i80.photobucket.com/albums/j169/marc780/Photobuck2AR_BOLT-017.jpg

[sinlessorrow]

I use the G and G tool and the green scotch brite pads (the ones without the aluminum strands in them, from the 99 cents store). My bolt is a stag chrome plated, so if this treatment were damaging the metal i'd see it.

Here's the G & G tool, it is only $19.95. Half the cost of the CRT-15. You shove in the bolt tail, the round steel blade bears against the carbon. You then rotate the bolt, and the steel blade scrapes off the carbon. The steel blade is not very sharp at all, but it is contoured properly to fit the curve of the bolt tail. They sell spare blades but the one that comes with it is two sided, if you wear out one end there's another end to use. Also the G & G people sell what are basically scotch brite pads cut into strips, for final finishing. I just buy a 3 pack of the pads at the store and cut them into 2 inch wide strips, and it is the same thing.
http://i80.photobucket.com/albums/j169/marc780/BCFinal.jpg

Here's pictures of my chrome plated bolt after 1000 rounds, is there any chance i am damaging it?

http://i80.photobucket.com/albums/j169/marc780/Photobucket-AR_BOLT-007.jpg
http://i80.photobucket.com/albums/j169/marc780/Photobuck2AR_BOLT-017.jpg

its hard to tell from the pics but the bolt tail does indeed appear to be much shinier than the bolt body, this would indicate less of a finish than the rest of the bolt that was not scrubbed with a brillo pad.

[Markasaurus]

That wouldn't surprise me - you're probably right, i may have scraped the chrome plate off. The chroming was not exactly top notch i don't think, I can't remember seeing chrome plating that wasn't SHINY.

I also have a titanium plated cam pin, i should have taken a picture of that too; the plating was totally gone, worn off from the part of the cam pin where it wears in the classic swirl pattern, after 100 rounds.

I have thought of getting the "Fail zero" parts but they are very pricey for the problem they are supposed to solve. Honestly if I had known how dirty the DI AR's get, and what a PITA to properly clean (dirty guns really bug me - yes, I have some kind of weird OCD, my apartments a mess but all my guns are spotless...)

Not to turn this into a piston gun post but allow me to stray a bit off topic for a minute....i wish i had bought the Stag 8 piston AR, it was less then $200 more at the same gun store. No worries about scraping bolts or carriers, just the piston. Some pics...i wonder how much they'd sell a conversion kit probably a lot...

Gas block on Model 8
http://i80.photobucket.com/albums/j169/marc780/STAG-PISTON2.jpg
Piston rod and spring and gas plug
http://i80.photobucket.com/albums/j169/marc780/STAGPISTON3.jpg
Piston and rod replaces gas tube
http://i80.photobucket.com/albums/j169/marc780/STAG_PISTON1.jpg

The bolt carrier...Stag claims the design eliminates bolt tilt.
http://i80.photobucket.com/albums/j169/marc780/STAGPISTONBOLT.jpg

[Col_Crocs]

okay, i've heard this so many times before i'm wondering by what mechanism the carbon 'self limits'?
does it build up to a certain point then not build up anymore? where does the subsequent carbon go after the previous carbon has self limited? does it build up then fall off? does it somehow lose adhesion to the bolt when it reaches a certain thickness?
just asking, as i'm curious.

I should've been more clear in my post. The idea it is self limiting has been put out there for a while now and I have come to agree with it for the most part. I dont think there is a specific point at which it no longer builds or that it no longer will at all, just that it doesn't go beyond the functional threshold. From my own observation of what little sample size I have of personal weapons and those from others I have handled, including a couple of high round count LE carbines... I have never seen carbon build up enough to affect function. My non-scientific take on it is, some of it gets blown off and becomes part of the loose gunk you can easily wipe off.

[sinlessorrow]

That wouldn't surprise me - you're probably right, i may have scraped the chrome plate off. The chroming was not exactly top notch i don't think, I can't remember seeing chrome plating that wasn't SHINY.

I also have a titanium plated cam pin, i should have taken a picture of that too; the plating was totally gone, worn off from the part of the cam pin where it wears in the classic swirl pattern, after 100 rounds.

I have thought of getting the "Fail zero" parts but they are very pricey for the problem they are supposed to solve. Honestly if I had known how dirty the DI AR's get, and what a PITA to properly clean (dirty guns really bug me - yes, I have some kind of weird OCD, my apartments a mess but all my guns are spotless...)

Not to turn this into a piston gun post but allow me to stray a bit off topic for a minute....i wish i had bought the Stag 8 piston AR, it was less then $200 more at the same gun store. No worries about scraping bolts or carriers, just the piston. Some pics...i wonder how much they'd sell a conversion kit probably a lot...

Gas block on Model 8
http://i80.photobucket.com/albums/j169/marc780/STAG-PISTON2.jpg
Piston rod and spring and gas plug
http://i80.photobucket.com/albums/j169/marc780/STAGPISTON3.jpg
Piston and rod replaces gas tube
http://i80.photobucket.com/albums/j169/marc780/STAG_PISTON1.jpg

The bolt carrier...Stag claims the design eliminates bolt tilt.
http://i80.photobucket.com/albums/j169/marc780/STAGPISTONBOLT.jpg

Move past your OCD. Carbon build u doesnt affect the rifle, run it wet and wipe it down when your done, thats honestly all you need.

[munch520]

No need to scrape it. Lube, ignore, drive on.

Boresnake, BCG wipedown, Slip2000 and 5 minutes is all it should take to 'clean' a carbine IMO.

Buildup is a sign you're using your rifle...which I view as a goooood thing :big_boss:


While on the subject and just out of curiosity, does anyone have any experiences with these yet?

C.A.T. M-4

Waste of money IMO. The scraper does nothing a spent casing wont. In either case, it's a waste of time.


That wouldn't surprise me - you're probably right, i may have scraped the chrome plate off. The chroming was not exactly top notch i don't think, I can't remember seeing chrome plating that wasn't SHINY.

I also have a titanium plated cam pin, i should have taken a picture of that too; the plating was totally gone, worn off from the part of the cam pin where it wears in the classic swirl pattern, after 100 rounds.

I have thought of getting the "Fail zero" parts but they are very pricey for the problem they are supposed to solve. Honestly if I had known how dirty the DI AR's get, and what a PITA to properly clean (dirty guns really bug me - yes, I have some kind of weird OCD, my apartments a mess but all my guns are spotless...)

Not to turn this into a piston gun post but allow me to stray a bit off topic for a minute....i wish i had bought the Stag 8 piston AR, it was less then $200 more at the same gun store. No worries about scraping bolts or carriers, just the piston. Some pics...i wonder how much they'd sell a conversion kit probably a lot...

There's never a reason to clean to the point of removing a finish/surface treatment.

IDK if the phrases "I wish I had bought" and "Stag" will ever cross my sober mind. Dumping a proven system for a shitty brand just because it 'runs cleaner'...this may be the wrong forum for that mindset. Just sayin.

[Markasaurus]

Boresnake, BCG wipedown, Slip2000 and 5 minutes is all it should take to 'clean' a carbine IMO.

Buildup is a sign you're using your rifle...which I view as a goooood thing :big_boss:



Waste of money IMO. The scraper does nothing a spent casing wont. In either case, it's a waste of time.



There's never a reason to clean to the point of removing a finish/surface treatment.

IDK if the phrases "I wish I had bought" and "Stag" will ever cross my sober mind. Dumping a proven system for a shitty brand just because it 'runs cleaner'...this may be the wrong forum for that mindset. Just sayin.
what's wrong with Stag?

The bolt is shot-peened, they use the full-auto bcg, a 5.56 barrel. And they have a lifetime warranty.

[sinlessorrow]

what's wrong with Stag? They are a subsidiary of CMT (continental machine and tool) and they have been making mil-spec uppers, lowers and ar parts for decades. Your top of the line AR might even have some of those parts in it.

The bolt is shot-peened, they use the full-auto bcg, a 5.56 barrel. And they have a lifetime warranty...does yours?

and bushmaster is a part of remington but that doesnt mean they are even close to quality

[Littlelebowski]

I have for the most part used BreakFree CLP, and personally I don't see what the big deal is.

It smells like camel taint and gives me PTSD.

[munch520]

what's wrong with Stag?

The bolt is shot-peened, they use the full-auto bcg, a 5.56 barrel. And they have a lifetime warranty.

A search will answer your question.

And to answer your inquiry before you edited it out, I believe mine is better because it has components that are known to be 'better' from BCM, Centurion, FN, Daniel Defense, etc.

But it has a 12" barrel...which isn't milspec. So I guess I should just shut up. And no, as an entire unit it doesn't have a lifetime warranty.


It smells like camel taint and gives me PTSD. :haha:
I'd say a prostitutes vag...or duck butter...but I don't wanna split hairs.

[HackerF15E]

I'd say a prostitutes vag...or duck butter...but I don't wanna split hairs.

Can't say I've ever smelled a beav that reminded me of CLP, or the other way around.

Maybe I'm hanging out with the right kind of women.

[Iraqgunz]

I have used CLP for many years and thank God I was able to escape into the modern age. CLP is total garbage and there is much better stuff on the market.

I have lubed .50 cals with CLP and watched it literally burn off after just a few hours while in Kuwait, Bahrain and Iraq.


I have for the most part used BreakFree CLP, and personally I don't see what the big deal is. It has worked fine for me in a variety of environments (arctic, desert, subtemperate forest).

I have also used it on a variety of systems; G3, HK416, Glock 17, MG-3, FN-MAG, Minimi, Browning M2 HMG with no issues.

I have tried Slip2000 as well, and I can't say I have experienced a noticeable difference. Not that I have done tests to find out though.

[munch520]

Can't say I've ever smelled a beav that reminded me of CLP, or the other way around.

Maybe I'm hanging out with the right kind of women.

Maybe she shoots a lot, was cleaning, and spilled it on her crotch?! :sarcastic:

Now a clam that smells like Slip...that's a classy woman!

[Markasaurus]

I have used CLP for many years and thank God I was able to escape into the modern age. CLP is total garbage and there is much better stuff on the market.

I have lubed .50 cals with CLP and watched it literally burn off after just a few hours while in Kuwait, Bahrain and Iraq.what lube do you use now?

[Redhat]

what lube do you use now?

His sig line(s) might offer a hint. :D

[Littlelebowski]

I have used CLP for many years and thank God I was able to escape into the modern age. CLP is total garbage and there is much better stuff on the market.


Preach it, brother!

Sent from my ADR6400L using Tapatalk 2

[Arctic1]

Well, for me it is hard to discredit something that has never failed me, be it hot deserts or freezing cold.

There might be better products, but CLP has worked for me so far.

[dangertree]

A search will answer your question.

And to answer your inquiry before you edited it out, I believe mine is better because it has components that are known to be 'better' from BCM, Centurion, FN, Daniel Defense, etc.


Known to be better? How so? Don't tell me to do a search, just tell me how? 40 years of manufacturing bolts for Colt, and everyone else, and the other brands are better how?

Particularly curious how BCMs branded bolt would be better.

Infomercial style group-think doesn't mean truth.

Facts please.

[mtdawg169]

While on the subject and just out of curiosity, does anyone have any experiences with these yet?

C.A.T. M-4
http://i45.tinypic.com/sc4d4y.jpg

In regards to the original post, in my limited experience (but as posted by several others as well) I found keeping my bolt assembly lubed helped keep a majority of the carbon off and what did stick was easily removed.

I have one and they work well. A quick couple of twists and you're done. There may still be a small amount of carbon left behind, but it will be inconsequential. I break mine out a couple of times a year when I get around to detail cleaning my ARs. It may not be completely necessary, but it's easy enough to do that it's part of my maintenance. I don't really clean on a regular schedule, just when the guns get especially nasty and I have some time on my hands.

Sent from my DROID RAZR using Tapatalk 2

[munch520]

Known to be better? How so? Don't tell me to do a search, just tell me how? 40 years of manufacturing bolts for Colt, and everyone else, and the other brands are better how?

Particularly curious how BCMs branded bolt would be better.

Infomercial style group-think doesn't mean truth.

Facts please.

Because folks that know more than you and me took the time to explain to me 'why'. And that's all there is to it. No amount of explaining/fact citing from me will convince you to ditch a part you are so emotionally attached to.

ETA: they may have started to put proper internals into their bolts, such as black extractor insert. But as I said, I'll just trust a company like BCM who makes one that's ready to roll.

[Plumber237]

If the carbon build up on the bolt tail does bother a particular person, buying a set of cheap dental picks works really well. I picked up a set for around $5, which since they're so cheap they aren't the ridiculously heavy duty picks. They are strong enough to scrape off carbon that has a little solvent on it, yet weak enough that they don't take the finish off the bolt tail.

Oh yeah and a big +1 for Slip2000 EWL. Besides the fact that it takes an eternity to burn off from firing, it seems so carbon resistant that after a long shooting day you can damn near wipe all the carbon off without even using solvent!

[dangertree]

Because folks that know more than you and me took the time to explain to me 'why'. And that's all there is to it. No amount of explaining/fact citing from me will convince you to ditch a part you are so emotionally attached to.

ETA: they may have started to put proper internals into their bolts, such as black extractor insert. But as I said, I'll just trust a company like BCM who makes one that's ready to roll.

You don't know me, or what I know. I don't believe anything without a reason, and I've never seen anything against Stag Arms that I couldn't chalk up to them not being an advertiser here.

I don't judge quality of a firearm by the color of the extractor insert.

Who makes those BCM bolts? I remember when CMT decided to mark their bolts with "CM" for a bit, BCMs bolts suddenly were marked CM. :dirol:

[Suwannee Tim]

Everybody basically says leave it alone. I can't.not only does it bother me to have a still-dirty gun, the metal underneath will pitt if you ignore the carbon long enough....

I have a Colt I bought in 1982, shot about 2K times, cleaned and lightly lubed and put away. Early this year I hauled it out and disassembled it. The carbon was still there, right where I left it 30 years ago but no evidence of corrosion. If there is corrosion under the carbon it will break right through and be conspicuously obvious. This has happened to my 5.45 mm which shoots corrosive ammo two or three times. It doesn't seem to hurt a thing as it didn't occur on a mating surface which surfaces don't accumulate carbon. The 5.45 doesn't corrode if given a hot water cleaning or oil bath even though the carbon is still there. I have never scraped the carbon from it, the amount of carbon retained seems to stabilize and causes no issues.

Here's a question for the OP: There is carbon building up under your gas block, did you know that? What are you going to do about it?

[polymorpheous]

You don't know me, or what I know. I don't believe anything without a reason, and I've never seen anything against Stag Arms that I couldn't chalk up to them not being an advertiser here.

I don't judge quality of a firearm by the color of the extractor insert.

Who makes those BCM bolts? I remember when CMT decided to mark their bolts with "CM" for a bit, BCMs bolts suddenly were marked CM. :dirol:

Come to troll for a fight?
This is not the forum for it.

That being said...
Stag has been know for tight chambers on marked 5.56mm barrels.
Sure BCM may get parts from CMT, (and so do many other manufacturers), but BCM sets forth very specific parameters for materials, stress relieving, QC testing, etc.
Stag may or may not hold themselves to same standards as BCM.

[munch520]

You don't know me, or what I know.

til you're username is red, blue, or yellow...I don't give a shit and assume you're just as clueless as I. Welcome to the club :sarcastic:

[Iraqgunz]

You don't know who makes the bolts for BCM either. I will tell you that they are not made by CMT.

They are made from Carpenter 158, shot peened, HP/MPI tested and they undergo a very thorough QA/QC process and hand inspection.


You don't know me, or what I know. I don't believe anything without a reason, and I've never seen anything against Stag Arms that I couldn't chalk up to them not being an advertiser here.

I don't judge quality of a firearm by the color of the extractor insert.

Who makes those BCM bolts? I remember when CMT decided to mark their bolts with "CM" for a bit, BCMs bolts suddenly were marked CM. :dirol:

[Littlelebowski]

You don't know me, or what I know.

You are quite right and we will continue not to give a **** as you play coy and beg for attention.

[khc3]

Just curious from a technical standpoint (understanding it's not a practical idea for a gun that is actually used), but has anyone ever soaked a carboned-up bolt in any solvent long enough for it to be just wiped off, or is that just not going to happen?

[Markasaurus]

Just curious from a technical standpoint (understanding it's not a practical idea for a gun that is actually used), but has anyone ever soaked a carboned-up bolt in any solvent long enough for it to be just wiped off, or is that just not going to happen?

I have been accused of OCD enough in this thread i'm now going to prove it, ha ha. I did some research on small arms and the nature of the carbon and the answer is probably no. You can soak it in almost anything you name, until you and I are collecting social security and the carbon will still be stuck on there like JB weld and will still need to be scraped off if you want it gone.

There is no chemical that will "dissolve" the carbon that wouldn't dissolve the bolt too. I have tried every chemical recommended by every BODY and not one of them had the slightest effect. The chemical composition of the carbon is such that nothing will dissolve it, it is not normal dirt it is different (remember that a diamond is basically WHAT substance?)
The statement made by some that "I use XXX lubricant and the carbon just wipes away and/or won't stick" is something i find hard to believe. I don't care if you are running a fail-zero bolt or whatever they come up with next year claiming to be even better - the carbon is going to stick to the bolt tail.

Photo is off somebody else's pitted bolt tail. I looked closely, its not carbon, dirt or anything else, it is pitting.

Got from here: http://vuurwapenblog.com/2011/10/05/how-well-do-melonite-and-nickel-boron-failzero-resist-corrosion-part-2/
http://i80.photobucket.com/albums/j169/marc780/93797124-race-to-politicize-shooting.jpg

[ErikS]

Anyone tried an ultrasonic cleaner/brass cleaner.

Not a tumbler of course.

I like my weapons clean and stay ahead of the carbon on the tail.

[madcratebuilder]

I've had some used bolt groups that were pretty nasty. I soak them in my carb tank for a few days. Any carbon left comes off with a small stainless toothbrush. A carb tank is not for the average gun owner, stinky and they well remove a few layers of skin if you don't use precautions.

[Littlelebowski]

Doesn't look like pitting, markasaurous. Looks like buildup.

[dangertree]

They are made from Carpenter 158, shot peened, HP/MPI tested and they undergo a very thorough QA/QC process and hand inspection.

...as do Stag Arms HP/MPI bolts.

[sinlessorrow]

I have been accused of OCD enough in this thread i'm now going to prove it, ha ha. I did some research on small arms and the nature of the carbon and the answer is probably no. You can soak it in almost anything you name, until you and I are collecting social security and the carbon will still be stuck on there like JB weld and will still need to be scraped off if you want it gone.

There is no chemical that will "dissolve" the carbon that wouldn't dissolve the bolt too. I have tried every chemical recommended by every BODY and not one of them had the slightest effect. The chemical composition of the carbon is such that nothing will dissolve it, it is not normal dirt it is different (remember that a diamond is basically WHAT substance?)
The statement made by some that "I use XXX lubricant and the carbon just wipes away and/or won't stick" is something i find hard to believe. I don't care if you are running a fail-zero bolt or whatever they come up with next year claiming to be even better - the carbon is going to stick to the bolt tail.

Photo is off somebody else's pitted bolt tail. I looked closely, its not carbon, dirt or anything else, it is pitting.

Got from here: http://vuurwapenblog.com/2011/10/05/how-well-do-melonite-and-nickel-boron-failzero-resist-corrosion-part-2/
http://i80.photobucket.com/albums/j169/marc780/93797124-race-to-politicize-shooting.jpg

you cant compare a bolt that has had corrosive 5.45 surplus through it to that of one with non corrosive 5.56.

of course it will have pitting if you leave it dirty using corrosive russian surplus. the diff is with 5.56 you will never have pitting caused by carbon.

[Littlelebowski]

That picture is very obviously buildup, not pitting. Note how the deposits are raised, not sunken.

[Littlelebowski]

...as do Stag Arms HP/MPI bolts.

We got it, you love your Stag. Good for you.

[sinlessorrow]

That picture is very obviously buildup, not pitting. Note how the deposits are raised, not sunken.

IDK......it does look like pitting and it did come from vuurwapenblog. the diff is it was a test to see how diff finishes worked with the corrosive 5.45 ammo when left to corrode.

so comparing it to 5.56 like the poster was trying was a poor attempt.

[Littlelebowski]

On a different device, I see both pitting and deposits now.

Funny thing is that I've got a pitted 5.45 bolt with over 23k rds on it. Just runs and runs. I'm certain the cleaning queens would have a fit over it :cray:

[Suwannee Tim]

Looks to me like someone went at it with a chipping hammer. I used to live in a house with a moisture problem and had a lot more rust than I really want to remember. It kind of desensitized me to corrosion. I don't regard a little corrosion as a horror especially on a working gun unless it is in the bore.

I'll put my LMT MRP / Spike's / 22 LR up against Little's 5.45 in the dirty contest any day. And I scraped some of the crud out of it and cleaned the bore last week. I haven't run across a neat freak at the range yet but I remain hopeful. My employer bought me a brand new AED which I carry with me on the clock and off. Maybe I'll get to use it.:D

Carbon is hard, strong and inert. It isn't easy to remove and it can't be disolved in anything short of a molten metal. The good news is the inert part. The carbon alone won't cause corrosion and neither will anything else in a non-corrosive cartridge.

I like to keep my bolt wet with oil on the theory that it penetrates the pores of the deposit then when heated by firing it flashes to a gas and spalls carbon off.

[GTifosi]

That picture is very obviously buildup, not pitting. Note how the deposits are raised, not sunken.


IDK......it does look like pitting

It is absolutely build up.
The gold colored stuff is on the surface and is the result of someone using a bronze bore brush to try unsuccessfully to clean the deposits, not tiny flakes /powder impregnated into the hardened machine steel.

The edge and shoulder that lead to the gas ring groove is clean and smooth, yet its the thinnest most easily damaged section of the entire piston area.
Any pitting would assuredly be most evident there first, yet its true and unmarked, because there's no damage/pitting and carbon won't stick there as the motion of the bolt in the carrier keeps it scraped clean.

[Dionysusigma]

I just give mine a quick media blast (what we use at work to remove paint from aluminum) every 1,000-1,200 rounds or so Also hit the inside rear of the carrier. Gets everything clean as a whistle and doesn't remove anything else.:)