View Full Version : Rockwell hardness on finishes
Caveat: please save me the inevitable "You don't need to clean that" when it comes to the bolt tail. I do and will continue to do so. This is a technical question.
Was looking at a company called TR-Enabling and a finish they have called Obsidian. They do a mil-spec BCG in it. It is a nickel-Teflon finish but has a Rockwell hardness of 70 (NP3 has a Rockwell of ~ 50). Now having spoken to Robar a few years ago I found out that using a brass/bronze bore brush to remove the bolt tail carbon deposits on NP3 is a no-go. So is the trusted old green scratchy pads we used in the Army. Have to use a nylon bore brush, and it takes a while to get my NP3 bolt tail spotless using that. My hard chrome bolts, where I can use a brass/bronze bore brush or scratchy pad, clean up really quick.
1) What is the Rockwell hardness of brass or bronze bore brush bristles?
2) I assume you can use a brush with a lesser Rockwell hardness on something with a higher one without removing the finish, right?
I'll bet tom12.7 has a slew of info! (hint hint)
Caveat: please save me the inevitable "You don't need to clean that" when it comes to the bolt tail. I do and will continue to do so. This is a technical question.
Was looking at a company called TR-Enabling and a finish they have called Obsidian. They do a mil-spec BCG in it. It is a nickel-Teflon finish but has a Rockwell hardness of 70 (NP3 has a Rockwell of ~ 50). Now having spoken to Robar a few years ago I found out that using a brass/bronze bore brush to remove the bolt tail carbon deposits on NP3 is a no-go. So is the trusted old green scratchy pads we used in the Army. Have to use a nylon bore brush, and it takes a while to get my NP3 bolt tail spotless using that. My hard chrome bolts, where I can use a brass/bronze bore brush or scratchy pad, clean up really quick.
1) What is the Rockwell hardness of brass or bronze bore brush bristles?
2) I assume you can use a brush with a lesser Rockwell hardness on something with a higher one without removing the finish, right?
I'll bet tom12.7 has a slew of info! (hint hint)
The typical copper alloys mentioned are measured using rockwell b scale, and fall in 55 to 90s.
Rockwell c is used for steels and hard materials, it used a different indenting device.
I really doubt brass or copper would do anything to np3, bronze I'm not sure. The metallic brush might take out any ptfe exposed on the surface but I'd imagine the nickel would protect everything else.
You could always try a Mr clean magic eraser.
Edit- is np3 has to be c scale right? A softer material will wear down a harder one over time, it just takes a long time.
The typical copper alloys mentioned are measured using rockwell b scale, and fall in 55 to 90s.
Rockwell c is used for steels and hard materials, it used a different indenting device.
I really doubt brass or copper would do anything to np3, bronze I'm not sure. The metallic brush might take out any ptfe exposed on the surface but I'd imagine the nickel would protect everything else.
You could always try a Mr clean magic eraser.
Edit- is np3 has to be c scale right? A softer material will wear down a harder one over time, it just takes a long time.
Hmmm.....off to Google.
I just use a paper towel and g96 clp. My sr25 bolt tail is a mirror. Chrome though. As to that np3 bcg...the locking lugs interface under many psi pressure with steel barrel extension, and the "skids" slide across type iiia ano with impunity...and robar says a copper brush is the devil? One of their claims...is not like the other.
Yeah, I sent a pm to the OP.
This was a "tech" I spoke to at Robar, not the owner or anything! He just said that using nylon brushes was optimal......but did say nichts on the bore brush or green scratchy pads.
RetroRevolver77
06-19-17, 11:43
I've often times wondered what the long term affects of running say a Nitrided or NicB carrier group in a standard anodized upper. If it wears pre-maturely or not.
I scrape the crap outta my bolt tails with a pick or jeweler's screw driver regardless of finish type. Standard bolts often rub to bare metal there on their own anyway.
I've often times wondered what the long term affects of running say a Nitrided or NicB carrier group in a standard anodized upper. If it wears pre-maturely or not.
Based on 3500 or so rounds I have on my setup, no, not really.
I had emailed the guys who do the Obsidian, TR-Enabling, with the very question I asked in the OP. Here is their response:
"You can use a brass brush however we would recommend using a standard plastic ap brush".
Not sure what an "ap" brush is. Nonetheless, it appears using a brass brush is not recommended.
tom12.7 likes hard chrome and so do I; you can see the dirt and use anything to get it off there.
RobertTheTexan
06-19-17, 19:47
All Purpose?
Sent from my iPhone using Tapatalk
I had emailed the guys who do the Obsidian, TR-Enabling, with the very question I asked in the OP. Here is their response:
"You can use a brass brush however we would recommend using a standard plastic ap brush".
Not sure what an "ap" brush is. Nonetheless, it appears using a brass brush is not recommended.
tom12.7 likes hard chrome and so do I; you can see the dirt and use anything to get it off there.
Chrome is awesome. People like to poo-poo it because its old tech, and hex chrome is bad for the environment and is a generally nasty chemical, not easy to work with, and good sources are becoming scarce.
But it fits into certain applications without a replacement.
NIB is really hard
Ni-ptfe is really corrosion resistant, but neither are direct replacements of chrome. I would choose NP3 as I don't clean the crap out of my stuff. Cr would be my 2nd choice in coatings all things equal.
I've come across the TR-Enabling as well. Have you looked at the Cryptic Coatings at all? IIRC, they're the retail arm of Toolcraft. Pricing is going to be around the same as TR, but Cryptic offers like 6 different coatings to choose from. All have varying degrees of friction coefficient, hardness, thickness of coating, etc. Their flagship is Mystic Black. Torture testing seemed to show it lives up to the hype.
Are you ultimately looking for hardness? If so, I believe DLC is king of that hill. It gets up into the 90s, but still retains some of the coefficient of friction advantages we see with the Nickel coatings.
I've long been hemming and hawing over purchasing a "fancy" coated bcg. Traditional has always worked, but I'd like to at least give one a shot. I simply can't decide. And it's a want, not a need. For now, I'll just continue to live vicariously through those who are able to make a decision :)
How do some of these coatings stack up against the coating LMT uses on their enhanced bolts? I believe LMT uses an Electroless Nickel coating of sorts on their enhanced bolts right? (I could be way wrong here, so forgive my lack of certainty).
If so, it looks like it could be comparable to the Nickel Teflon coating mentioned in the OP, so long as it's heat treated correctly.
"A typical hardness of electroless Nickel, as deposited is in the range 450-480 H.V. (46-48 Rockwell C.) However, the deposits can be precipitation hardened by heat treatment at 400°C for one hour, to 800-950 H.V. (64-68 Rockwell C.) This heat treatment will also improve adhesion and wear resistance."
http://www.hardchrome.com.au/technologies/electroless-nickel/
Hopefully someone more knowledgeable can break down the differences.
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How do some of these coatings stack up against the coating LMT uses on their enhanced bolts? I believe LMT uses an Electroless Nickel coating of sorts on their enhanced bolts right? (I could be way wrong here, so forgive my lack of certainty).
If so, it looks like it could be comparable to the Nickel Teflon coating mentioned in the OP, so long as it's heat treated correctly.
"A typical hardness of electroless Nickel, as deposited is in the range 450-480 H.V. (46-48 Rockwell C.) However, the deposits can be precipitation hardened by heat treatment at 400°C for one hour, to 800-950 H.V. (64-68 Rockwell C.) This heat treatment will also improve adhesion and wear resistance."
http://www.hardchrome.com.au/technologies/electroless-nickel/
Hopefully someone more knowledgeable can break down the differences.
Sent from my SM-N910P using Tapatalk
LMT is kinda cagey about what exactly the finish is. "Proprietary" is usually what you hear. That said, I have two Enhanced BCG's and love 'em. Yes, they do clean up easily and I'm not careful about what I use to clean them either.
Chrome is awesome. People like to poo-poo it because its old tech, and hex chrome is bad for the environment and is a generally nasty chemical, not easy to work with, and good sources are becoming scarce.
But it fits into certain applications without a replacement.
NIB is really hard
Ni-ptfe is really corrosion resistant, but neither are direct replacements of chrome. I would choose NP3 as I don't clean the crap out of my stuff. Cr would be my 2nd choice in coatings all things equal.
I look at it like this: the piston on every modern military small arm (since WWII, and even then many were) is chromed. The bolt on an AR is essentially the piston, so why not?
How do some of these coatings stack up against the coating LMT uses on their enhanced bolts? I believe LMT uses an Electroless Nickel coating of sorts on their enhanced bolts right? (I could be way wrong here, so forgive my lack of certainty).
If so, it looks like it could be comparable to the Nickel Teflon coating mentioned in the OP, so long as it's heat treated correctly.
"A typical hardness of electroless Nickel, as deposited is in the range 450-480 H.V. (46-48 Rockwell C.) However, the deposits can be precipitation hardened by heat treatment at 400°C for one hour, to 800-950 H.V. (64-68 Rockwell C.) This heat treatment will also improve adhesion and wear resistance."
http://www.hardchrome.com.au/technologies/electroless-nickel/
Hopefully someone more knowledgeable can break down the differences.
Sent from my SM-N910P using Tapatalk
Electroless is the method, not necessarily the coating.
High phosphorus engineering nickel can be deposited electroless, or electroplated.
NiB and NP3 (Nickel-ptfe/Teflon composite) are both typically deposited electrolessly for uniformity.
To deposit a metal, it needs to be oxidized to get it into solution, then reduced onto the substrate. This can be done chemically (electroless) or electrochemically (electrons reduce the ions on the cathode and oxidize them on the anode).
The method, the chemicals used as the "carriers"(anions in solution), and many other factors can influence the deposit structure and properties.
Then you have heat treatments which further alter the deposits.
Straight Shooter
06-20-17, 05:55
I had emailed the guys who do the Obsidian, TR-Enabling, with the very question I asked in the OP. Here is their response:
"You can use a brass brush however we would recommend using a standard plastic ap brush".
Not sure what an "ap" brush is. Nonetheless, it appears using a brass brush is not recommended.
tom12.7 likes hard chrome and so do I; you can see the dirt and use anything to get it off there.
The ap..All Purpose brush is the standard issue green toothbrush in the old gov issue cleaning kits. Remember the two heads..one big & one small? That's it.
I also scrape mine with a pick or a small screwdriver like MarkM said...I didn't wanna say that cause I figured Id get lectured that I was "gonna scratch/gouge/ruin the bolt by doing that. Done it for years with no probs yet.
The ap..All Purpose brush is the standard issue green toothbrush in the old gov issue cleaning kits. Remember the two heads..one big & one small? That's it.
I also scrape mine with a pick or a small screwdriver like MarkM said...I didn't wanna say that cause I figured Id get lectured that I was "gonna scratch/gouge/ruin the bolt by doing that. Done it for years with no probs yet.
Oh okay, I know what it is now, thanks. Never heard it referred to as "ap". I also have one with brass bristles; works well but deforms quickly.
Straight Shooter
06-20-17, 09:35
I had emailed the guys who do the Obsidian, TR-Enabling, with the very question I asked in the OP. Here is their response:
"You can use a brass brush however we would recommend using a standard plastic ap brush".
Not sure what an "ap" brush is. Nonetheless, it appears using a brass brush is not recommended.
tom12.7 likes hard chrome and so do I; you can see the dirt and use anything to get it off there.
Oh okay, I know what it is now, thanks. Never heard it referred to as "ap". I also have one with brass bristles; works well but deforms quickly.
Most welcome Sir. Pronounced A-P..not ap like a phone app tho.
Singlestack Wonder
06-20-17, 10:50
My goto finish for many years has been Melonite QPQ (known under many other names, i.e. black nitride, etc.). It has a rockwell hardness of ~55 and is a surface treatment vs. coating, plating, etc. which adds to potential dimensional issues. Impervious to rust, heat, etc., it is now the goto finish for many firearms manufacturers. Back when I utilized 1911's, all were melonite qpq treated (if I touch a blued or stainless pistol, rusty fingerprints would appear in an hour).
http://www.blacknitride.com/frequentlyaskedquestions.html
I look at it like this: the piston on every modern military small arm (since WWII, and even then many were) is chromed. The bolt on an AR is essentially the piston, so why not?
Why not?
Well, there are several reasons, depending on the exact type of chromium finish.
There are two distinct types of technical chromium electro-plating:
1) Hard Chrome plating (HC, AMS2406) - HC is NOT recommending for highly stressed parts like bolts. The reason is hard chrome plating, by the nature of its application leaves micro-cracks in the surface, which are stress risers. These are fatigue initiation points if the part is subjected to stress. Pistons are not subjected to very high stresses, bolt lugs are.
2) Thin Dense Chrome (TDC, AMS2438) - TDC is a different type of chromium plating that, well, is thinner and denser than HC. It also has a smooth crack-free surface, so its resistance to fatigue cracking is much better than HC.
TDC usually goes by various trade names such as Electrolizing, Armoloy, Electralloy, etc.
You can deposit a HC film as thin as 0.0002” however, that does not make it TDC, the difference between HC and TDC goes beyond what Specifications cover. It is related to chemistry, current density, temperature, etc. The deposit is different regarding physical and mechanical properties.
The original bolt and carrier for the AR-15 were never hard chrome plated. They were Electrolized (TM) by Electrolyzing Inc of Los Angeles, Not only was the process more expensive, but Electrolyzing Inc was unwilling to license their proprietary TDC process to anyone, and would have been unable to keep up with the high volume, full rate production of M16 would entail.
LMT is kinda cagey about what exactly the finish is. "Proprietary" is usually what you hear.
I noticed that, there were only a few places that even remotely hinted at what it actually was. I've been on the fence on ordering one for suppressed use while I wait for the stamp for my RC2. I may just have to do it.
.
Great comment, and thank you for the response. There are so many wonder coatings out there now that it's difficult to keep up with, especially when they seem so similar. It'd be nice if there was an in depth test done between the most popular choices, but I assume that would be a pricey endeavor.
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