Buffer Type?

[Shihan]

Im sure this has been asked to death but what ype of buffer should be used with a 16" carbine?
Also what type comes standard from the factory with a
M&P15T
LMT lower ?


Thanks

[Robb Jensen]

With your set up I'd use an H buffer.

S&Ws come with a CAR buffer from the factory.

The H will help slow it down and stop any extraction issues. I'd also be sure it had a black extractor buffer and I'd use a Crane 0-ring or MGI D-fender extractor enhancer over the extractor spring.

[LukeMacGillie]

Use the buffer that comes with the gun, up until such point that the gun does not run. Then consider respringing/buffering.

[twl]

Often the one that comes with the gun when new is the best one to start out with.

As time goes on, you may experience some gas port erosion, which would cause the gas port to enlarge, thereby altering the balance between the gas metering and the moving masses(which includes the buffer). This changes the cycling behavior.

You can help to restore the balance after that occurs by using a heavier buffer.
The buffer should allow good function of the weapon with a variety of ammunition, and in a variety of operating temperatures.

Too heavy buffers can cause short-stroking, and too light buffers can cause overcycling. Strive for a good balance.

[Shihan]

Im making a parts order for a customer this week so I figured I would pick up some stuff for myself while I was at it and had no idea what type to order for myself. Life was easy when I would just have the armorer do anything that was needed.

So to verify from the factory

S&W M&PT uses a standard Car buffer?

LMT uses a H-Buffer?

Thanks

[tiger seven]

My LMT lower came with a standard carbine buffer in it.

Derek

[Shihan]

I called LMT and they said the H-buffer would work better and then I called Stag and they said the standard buffer would work better unless I was using the weapon on full auto.
Is there any down side to using a H-buffer?

[Robb Jensen]

I called LMT and they said the H-buffer would work better and then I called Stag and they said the standard buffer would work better unless I was using the weapon on full auto.
Is there any down side to using a H-buffer?

If using very weak ammo it might not lock the bolt back.

[msr]

How about a buffer recommendation for an 11.5"?

[Robb Jensen]

How about a buffer recommendation for an 11.5"?

H to H2.

[watchluvr4ever]

My brand new LMT CQB length MRP with 16" barrel came with a CAR buffer. Should I leave it be or put in a heavier buffer? If yes what buffer? BTW, I haven't shot it yet because I'm waiting on my sights. Thanks!

[welchtactical]

I've been using the H buffers for a while now with a Wolff extra power spring. Seem to work pretty well. A must with Piston ARs IMHO.

[Robb Jensen]

My brand new LMT CQB length MRP with 16" barrel came with a CAR buffer. Should I leave it be or put in a heavier buffer? If yes what buffer? BTW, I haven't shot it yet because I'm waiting on my sights. Thanks!

LMTs run slightly small gas ports and run fine on CAR weight buffers. I'd just run a CAR buffer.

[Buckaroo]

At the risk of outing myself as a real noob.....

What does a piston upper need a buffer for?

[Robb Jensen]

At the risk of outing myself as a real noob.....

What does a piston upper need a buffer for?

The buffer is the thing that pushes the carrier forward again. Regardless if an AR is direct impingment or piston it still needs a buffer.

[Buckaroo]

So there must be an "H" buffer for a piston system.

That makes sense. It just confused me when the discussion went from DI to Piston uppers and it appeared that the buffers were the same.

I have no exposure to Piston uppers so thanks for helping me learn something!

[Robb Jensen]

So there must be an "H" buffer for a piston system.

That makes sense. It just confused me when the discussion went from DI to Piston uppers and it appeared that the buffers were the same.

I have no exposure to Piston uppers so thanks for helping me learn something!

A H buffer is a H buffer regardless of the type of upper on the lower.

It's like saying there two different 17" Wheels for Mustangs (one for supercharged models and another for naturally aspirated models). The wheels don't know. ;)

[C4IGrant]

The gas port size in the gun plays a big part in the equation. LMT uses very small gas ports in the 10.5's as they are intended to run on FA. So generally I would run no more than an H buffer in these weapons.

For most any other weapon with a carbine gas system. I would run either an H or H2 and a quality spring (CS is preferred).

All Stag, S&W, BM, RRA, DPMS, Oly and LMT's come with carbine buffers.

Colt is one of the few companies that ships their weapons with H and sometimes an H2 buffer.


C4

[Buckaroo]

A H buffer is a H buffer regardless of the type of upper on the lower.

It's like saying there two different 17" Wheels for Mustangs (one for supercharged models and another for naturally aspirated models). The wheels don't know. ;)

OK, so I am off to research piston uppers. Thanks for helping!

[UPSguy]

I understand that if you have too heavy of a buffer a sympton is failure to lock open. How do you know if you need a heavier buffer?

[Robb Jensen]

I understand that if you have too heavy of a buffer a sympton is failure to lock open. How do you know if you need a heavier buffer?

Hard extraction.

[Shihan]

LMTs run slightly small gas ports and run fine on CAR weight buffers. I'd just run a CAR buffer.

Gene Swanson recommends running H-buffers in their carbines for what its worth.

[Robb Jensen]

Gene Swanson recommends running H-buffers in their carbines for what its worth.

Interesting since LMTs ship with CAR buffers.

[Shihan]

Interesting since LMTs ship with CAR buffers.

Weird isnt it? They say they can ship with a Hbuffer if asked.


Email back and forth from LMT

Do you recommend the Hbuffer for Semi auto's?



Thanks

Chris



I run H buffers in all of our rifles. From 10.5 up to the 16 inch. I also run a lot of full auto so the H buffer slows things down a bit.



Gene Swanson

Technical Specialist

Lewis Machine and Tool Co.

1305 W 11th Street

Milan, IL 61264

PH:309-787-7151

FX: 309-787-7193

SwansonG@lewismachine.net


--------------------------------------------------------------------------------


Sent: Monday, August 20, 2007 7:16 AM
To: Swanson, Gene
Subject: Re: Info?



Hi Gene what buffer do you recommend for your 14.5 carbine?



Thanks

[taliv]

i don't suppose there's a picture thread somewhere comparing all the different buffers you guys have been talking about?

i'm not sure i could pick any of them out of a lineup.

[UVvis]

i don't suppose there's a picture thread somewhere comparing all the different buffers you guys have been talking about?

i'm not sure i could pick any of them out of a lineup.

Generally they all look the same, but are stamped on the face.
Car = blank
H = "H"
H2 = "H2"
H3 = "H3"
9mm buffers are generally solid and dark.

Randall (I think) has a good picture of buffers with the spacers and weights showing, see below.

Here is the thread: http://m4carbine.net/showthread.php?t=6827

And the pic from that thread. Randall, I hope you don't mind me listing this here, but it is on the other thread....

http://ar15barrels.com/tech/buffer-construction.jpg

[Hootiewho]

I just got one of my 6933's (11.5")back from SAW having the reliability package performed on it; it originally came with an H buffer, but they installed an H2 buffer. I was told in an email by Ken at SAW once before to run an H3 buffer in a commando lenght barrel especially if suppressed though. They sell the H3 buffer as Commando buffer, so I may give them a call Monday to make sure that the H2 is right. Will report back.

[TWR]

I have a couple of questions.

What about carbines that came with non collapsing stocks (rifle stocks)? Do they drill the gas ports differently for those?

Also what buffer would you run in a midlength?

[UVvis]

I have a couple of questions.

What about carbines that came with non collapsing stocks (rifle stocks)? Do they drill the gas ports differently for those?

Also what buffer would you run in a midlength?

In my two mid-length guns I've been running standard recoil springs and H2 buffers. I haven't run into any feeding problems. Don't know if a H would be better, but the H2's have worked fine for me with my BCM and Sabre middy guns.

I think the gas port hole is drilled to a pre-determined sized based on where the port is in relation to the barrel, and relation to the muzzle. Not based on what type of stock you plan to have

[TWR]

In my two mid-length guns I've been running standard recoil springs and H2 buffers. I haven't run into any feeding problems. Don't know if a H would be better, but the H2's have worked fine for me with my BCM and Sabre middy guns.

I think the gas port hole is drilled to a pre-determined sized based on where the port is in relation to the barrel, and relation to the muzzle. Not based on what type of stock you plan to have

Carbines came with rifle stocks including the 5 oz buffer and then some had collaspable stocks with the 3 oz buffer. Now there's all this talk about running heavy buffers may cause short stroking, i just don't understand.

[AR15barrels]

Something to ponder here...

The "standard" AR or M16 gas system used a 5oz buffer (A2) and a lightweight action spring.
This is the smoothest running setup.
When they chopped off the stock to make a carbine, there was not enough room for 5oz of weights anymore so carbine buffers weigh 3oz.
The spring tension got bumped up to help account for the loss of buffer weight.

Now, we see the trend towards heavier and heavier carbine buffers by installing 1, 2 or 3 tungsten weights.
What we don't see is the reduction of spring rates accordingly.
This is mostly because most carbines are over-gassed to begin with.
With a properly gassed barrel and an H3 buffer, it should be necessary to clip some coils off the spring in order to solve the short stroking.
The fact that most barrels won't short stroke with an H3 buffer and stock carbine spring is just further proof that the barrel is over-gassed.

I have measured and documented literally hundreds of gas ports.
I have a real good idea when gas port sizes should be on different gas system and barrel lengths.

[jmart]

I think the gas port hole is drilled to a pre-determined sized based on where the port is in relation to the barrel, and relation to the muzzle. Not based on what type of stock you plan to have

Fair enough, but carbine uppers are typically paired with collapsible stock lowers which use different springs (length and spring rate) and buffer weights than A2 stocks. And the A2's are paired with rifle length gas systems. I can't recall anyone who offers carbine barrels on A2 lowers, can you? So it does beg the question about whether or not you should run a carbine spring/buffer setup with a spacer in an A2 stock rather than a rifle-weight buffer and spring. Any thoughts?

[AR15barrels]

I hope you don't mind me listing this here, but it is on the other thread....

Feel free to post ANY of my technical pictures when it helps to explain something.
I keep them all in this folder (http://ar15barrels.com/tech)

All I ask is that you read and comply with the "read this first" (http://ar15barrels.com/tech/!!!read-this-first!!!.txt) file.

[AR15barrels]

Fair enough, but carbine uppers are typically paired with collapsible stock lowers which use different springs (length and spring rate) and buffer weights than A2 stocks. And the A2's are paired with rifle length gas systems. I can't recall anyone who offers carbine barrels on A2 lowers, can you? So it does beg the question about whether or not you should run a carbine spring/buffer setup with a spacer in an A2 stock rather than a rifle-weight buffer and spring. Any thoughts?

Whenever an A2 buffer and spring are an option, they are ALWAYS the better solution.

[jmart]

Whenever an A2 buffer and spring are an option, they are ALWAYS the better solution.


So then with a carbine/collapsible stock, should the only decision be whether or not to run a H2 vs 9mm buffer? Or does the different spring rate of the carbine spring change the system enough where it's not simply a matter of matching carbine buffer weights as closely as possible to a rifle buffer?

[AR15barrels]

does the different spring rate of the carbine spring change the system enough where it's not simply a matter of matching carbine buffer weights as closely as possible to a rifle buffer?

Yes, so don't automatically assume you need an H2 or 9mm buffer.
This will vary more depending on port size and barrel length than anything else.
An LMT 10.5 would certainly short-stroke with a 9mm buffer, but a Colt 10.5" NEEDS a really heavy buffer.
Colt's gas ports run around 0.015" larger than LMT's which is a HUGE difference in the same length barrel and gas system.

In general, run the heaviest buffer that does NOT cause short stroking.
So keep going heavier until it short strokes, then back down to the next lightest buffer.
This will put you in the sweet-spot of function.
The action will run cleaner.
Brass will not get as beat up either.

[UVvis]

I also don't think all carbine springs are the same power, just to compound the issue. Which might make ordering multiple springs from the same lot make more sense.

[AR15barrels]

I also don't think all carbine springs are the same power, just to compound the issue. Which might make ordering multiple springs from the same lot make more sense.

Not just that, but the spring changes power as you use it.
A brand new spring is stronger than a spring with 3K rounds fired.
So if you find the sweet setup, but then go shoot 3K rounds, you MAY need to go to the next heavier buffer to get back to that sweet setup again.
Compound this with gas port erosion on carbine gas systems and you really see a change in how the gun functions over the life of the parts.

[TWR]

Thanks Randall, I did not know rifle length springs were weaker than carbine springs. That makes sense and answers a few other questions I've had.

So adding Colts plastic buffer and shaved bolt carrier, really kind of got things out of kelter I bet. I have one gun that came with both and after I changed them out it still ran perfectly. I did change the spring to an extra power CS spring and that caused short stroking with most ammo, so sounds like I got that one pretty close. For now anyway.

[Bob Reed]

Hello Randall,

Sir, in your view, why wouldn't LMT (or anyone for that matter) just drill their ports to Colt's spec's? Wouldn't it achive more consistency amoung different buffer weights & ammo?

Also, outta all the current makers, who does use Colt's port sizes?

Edited to add: Sorry if my question is a bit off topic, I'm not trying to drift the thread.

Thanks.

[PaigeB]

What type of buffer should I use for an 16" LMT shooting 6.8?

[C4IGrant]

What type of buffer should I use for an 16" LMT shooting 6.8?


I would try an H2 and see what you get.



C4

[JLM]

I have heard that LMT changed the port size on the 10.5's over time, in an effort to get more commercial ammunition to run. Anyone know for sure, or are they still using smaller ports?

[AllAmerican]

Has anyone had any expierience with the AR-restor??? It is shown in the Guns & Ammo mag. the Book of the AR15, as one of the top ten accesories to look at. It is called the Enidine AR-restor Recoil Reducer.

[C4IGrant]

Has anyone had any expierience with the AR-restor??? It is shown in the Guns & Ammo mag. the Book of the AR15, as one of the top ten accesories to look at. It is called the Enidine AR-restor Recoil Reducer.

Not needed. Maybe if you are running FA and wanted to reduce your rate of fire, but that would be the only reason.


C4

[petey1]

What would be a good buffer choice for a Stag 16" carbine upper and would that recommendation be different based on the stock choice (collapsable vs. fixed)? Thanks in advance for helping a newb out;)

[AR15barrels]

What would be a good buffer choice for a Stag 16" carbine upper and would that recommendation be different based on the stock choice (collapsable vs. fixed)? Thanks in advance for helping a newb out;)

Depends on the length of fixed stock.
There are two different lengths of buffers.

http://ar15barrels.com/tech/stocks.jpg

It makes no difference if the stock is fixed or collapsible if both styles of stock you are comparing use the carbine length buffer/spring.
If you are comparing an A2 stock to collapsible stocks, then you would certainly run an A2 buffer/spring in the A2 stock and a Carbine buffer/spring in the collapsible stock.

[petey1]

Depends on the length of fixed stock.
There are two different lengths of buffers.

http://ar15barrels.com/tech/stocks.jpg

It makes no difference if the stock is fixed or collapsible if both styles of stock you are comparing use the carbine length buffer/spring.
If you are comparing an A2 stock to collapsible stocks, then you would certainly run an A2 buffer/spring in the A2 stock and a Carbine buffer/spring in the collapsible stock.

Thanks. Would an H buffer be a good choice in a carbine length (collapsible) Stag if I were starting from scratch (a build)? I guess I'm still wondering if an H buffer is necessary, or should I try the "standard" carbine weight buffer first (and work up if need be)? Thanks again.

[Robb Jensen]

Has anyone had any expierience with the AR-restor??? It is shown in the Guns & Ammo mag. the Book of the AR15, as one of the top ten accesories to look at. It is called the Enidine AR-restor Recoil Reducer.

They weigh almost was a H2 weighs but also have the benefit of being hydraulic. They do make locking the bolt back manually more difficult for the last 3/4" or travel, if you're not paying attention you might lock it back on the carrier and not the face of the bolt. They do make the felt recoil feel 'softer' especially if combined with a muzzle brake/comp.

[TacDoc]

I have heard that LMT changed the port size on the 10.5's over time, in an effort to get more commercial ammunition to run. Anyone know for sure, or are they still using smaller ports?

I just got my LMT 10.5 upper last month and it ran flawlesly with regular, H, H2 and H3 buffers and a USGI carbine spring. I also tried an ISMI spring and it didnt hold the bolt open at the last round, even with the regular buffer. I keeped the H3 buffer with this rig because less recoil was felt. The ammo I use with my 10.5 is Federal AE 55gr and BB Black Hills 75 & 77gr.

I installed a Larue 7.0 rail in this upper and forgot to measure the gas port... :rolleyes:

[AR15barrels]

Thanks. Would an H buffer be a good choice in a carbine length (collapsible) Stag if I were starting from scratch (a build)? I guess I'm still wondering if an H buffer is necessary, or should I try the "standard" carbine weight buffer first (and work up if need be)? Thanks again.

16" carbine gassed barrels are the biggest offenders when it comes to being over-gassed due to the excessively long dwell time.
I would run the heaviest buffer that you can get away with.
Certainly start with an H or H2 right away.

If you are considering an A2 stock, then a regular A2 buffer is the setup as it's heavier than all but an H3 or 9mm buffer.

http://ar15barrels.com/tech/buffer-construction.jpg

[AllAmerican]

Not needed. Maybe if you are running FA and wanted to reduce your rate of fire, but that would be the only reason.


C4

Another question... How often should a buffer spring be replaced?? I have been a heavey user of the M4 in the military, and if not mistaken I had the same weapon (at one time) for at least 3 years. Now I am a user, not an armorer. I don't remember ever haveing any service done unless it was done in armory and I was not aware of it. I have searched but could not find any info in the archives. My rifle now is a short flattop BM.

Thanks Grant!

[C4IGrant]

Another question... How often should a buffer spring be replaced?? I have been a heavey user of the M4 in the military, and if not mistaken I had the same weapon (at one time) for at least 3 years. Now I am a user, not an armorer. I don't remember ever haveing any service done unless it was done in armory and I was not aware of it. I have searched but could not find any info in the archives. My rifle now is a short flattop BM.

Thanks Grant!


If the spring is SS, then every 3-5K it should be replaced. This type of PM would have been done by your armorer and you wouldn't have known about it.

If the spring is CS, then I would change it out about ever 8K (or longer).


C4

[jmart]

Another question... How often should a buffer spring be replaced?? I have been a heavey user of the M4 in the military, and if not mistaken I had the same weapon (at one time) for at least 3 years. Now I am a user, not an armorer. I don't remember ever haveing any service done unless it was done in armory and I was not aware of it. I have searched but could not find any info in the archives. My rifle now is a short flattop BM.

Thanks Grant!


Check Robb's post at the end in this thread (http://m4carbine.net/showthread.php?t=6827) from the Tech Board. replace when springs fall below the min lengths listed.

[AllAmerican]

YES!!!! That is information I was looking for! I would like to pick up a spare, in case the election comes out the wrong way......
Thanks Again!!!

[kittyhawk]

Great info guys. My problem is I just got a new 14.5 LMT upper and put on a New RRA lower with factory carbine buffer and spring. I pulled apart my buffer and it is 1 chunck of steel not the Small ones like were in the Pics and the Spring measures10 5/8: It functions great with all ammo But Wolf which is what I have Lots of. What would you suggest besides scraping the Wolf. Would swapping out buffers or springs be the way to go?

Thanks

Dave

[Robb Jensen]

Great info guys. My problem is I just got a new 14.5 LMT upper and put on a New RRA lower with factory carbine buffer and spring. I pulled apart my buffer and it is 1 chunck of steel not the Small ones like were in the Pics and the Spring measures10 5/8: It functions great with all ammo But Wolf which is what I have Lots of. What would you suggest besides scraping the Wolf. Would swapping out buffers or springs be the way to go?

Thanks

Dave

Your upper should run fine on a CAR weight buffer. If it gives you extraction problems go up to an H buffer.

[kittyhawk]

Oh it extracts just fine it just short strokes. I was using Fed 55gr bt, prvi 75gr hpbt and those worked Great, it's just the dam Wolf kept Short stroking, I had the Same Problem with a New S&W Tac, it was sent back last week. Problem is my wife got me 1000 rounds of wolf for Xmass( god bless her but she knows nothing about ammo and the idot at the local shop recomended it and was Cheap.) and I need to shoot it all up and not waist it.
I hope to find a cure soon.

Thanks

Dave

[Robb Jensen]

Wolf is weak and you shouldn't base your reliability opinions on it. If the rifles runs well on brass cases ammo then stick with brass cased ammo. I don't suggest anyone shoot Wolf in a DI gas AR. Piston AR? No problem.

[kittyhawk]

Thanks for the Input, I know wolf is week so it will get ran through my Saber Middy, It eats it with 0 Problems. Just ordered 1000 rounds Prvi 55fmj.

Thanks for all the help. Thats why I like this site so much the knowledge factor is through the Roof and everyone is willing to help one-another
out.

Dave

[HTTTRH]

Is there a "How to" guide with pics on a buffer swap? Here or any other site?

[RE4]

Its a brainless procedure- separate your upper and lower, depress the metal stub holding back the buffer and spring and your buffer/ spring pops out from the extension tube. take out the old buffer and replace with new one.

I did it in less than minute.

I cant wait to try out the 9mm buffer tomorrow. I'll report back (i'll even put the standard back in and compare..)

[RE4]

Its a brainless procedure- separate your upper and lower, depress the metal stub holding back the buffer and spring and your buffer/ spring pops out from the extension tube. take out the old buffer and replace with new one.

I did it in less than minute.

I cant wait to try out the 9mm buffer tomorrow. I'll report back (i'll even put the standard back in and compare..)

[ROADKING]

Well how did it do. ?????????

[EzGoingKev]

I have a Colt 6920 and the bolt is the older style with the unshrouded firing pin and milled out rear section. It came with an "H" buffer.

I have read that the latest spec on the 6920 is the M16 bolt with the "H2" buffer. I do not know what they did regarding the spring.

[jwinch2]

OK, so does anyone have a good recommendation on a reputable H buffer to purchase? I have an LMT which was shipped with a CAR buffer.

Cheers,

Jason

[C4IGrant]

OK, so does anyone have a good recommendation on a reputable H buffer to purchase? I have an LMT which was shipped with a CAR buffer.

Cheers,

Jason

We have LMT H buffers in stock.



C4

[jwinch2]

We have LMT H buffers in stock.



C4

Cool, I'll check it out. I'm assuming you can use the spring that came with the CAR buffer or that the H buffer would come with a new spring? Thanks!

[3678barnes]

Very informative thread. I am putting a Noveske 18" SPR barrel on a Colt rifle. I plan to replace the full stock with a VLTOR carbine stock. Can someone recommend which buffer I should install?

[ROADKING]

I have always heard the stock buffer works good.

[QuietShootr]

If the spring is SS, then every 3-5K it should be replaced. This type of PM would have been done by your armorer and you wouldn't have known about it.

If the spring is CS, then I would change it out about ever 8K (or longer).


C4

An important point when talking about CS buffer springs: Make sure you're talking about the standard-power CS spring, not the XP CS spring. The standard-power CS springs (available from Brownells) are great. The XPs are a solution in search of a problem to cause.

Edit for my opinions on buffering (worth what you're paying for it):
Add the standard power CS spring from Brownells before you do anything else. Then:

5-round lockback test: using a known good magazine and five single rounds. Single load one round at a time, and holding the weapon very loosely, fire the shot. The weapon must lock back on an empty magazine 5 times to be considered a GO for that combination.

16" bbl, carbine length gas: try the 5-single round lockback test with an H2 and commercial ammunition. If successful, rapid fire 16 rounds (4 each) through the weapon, rotating it in all 4 positions (0, 90, 180, 270 degrees, held loosely.) If it runs, go to H3 and repeat. If it runs, go to Colt 9mm buffer and repeat. If it works, dump two magazines of commercial while holding the gun loosely. If it cycles and locks back, you're good to go.

14.5bbl, carbine length gas: try the 5-single lockback test with commercial ammo. if it runs, go to the H buffer. Repeat. If successful, rapid fire 16 rounds (4 each) through the weapon, rotating it in all 4 positions (0, 90, 180, 270 degrees, held loosely.) if it runs, go to H2. Repeat. if it runs, go to H3 or 9mm. Repeat the test. IF it works, you're GTG. STOP when the weapon short strokes or otherwise fails to feed, and repeat the previous test. If the weapon passes, the previous weight is the correct one for your weapon.

10.5" LMT: Repeat 14.5 procedure.

16" bbl, midlength: test as above, but start with CAR buffer and work no higher than H2.

JMO, of course, subject to change when I'm not communing with John Barleycorn.

[Jaeger]

I tried an H2 and an extra power CS spring ( http://www.sprinco.com/tactical.html )in my N4 and it puked regularly. It runs well with the supplied H buffer and standard spring.
That's a good testing procedure Quietshootr. Thanks for posting it. I think I'll get the H3 and 9mm and a CS standard spring with my next order and try those combinations.

[liftman]

Wow this thread has been around a while. I'll keep it going with another noob question.

It seems that most of the talk in this thread is concerning DI systems and not really anything about piston systems. I'm gathering info on some builds I'm starting, and was wondering what to use for buffers and springs in a carbine stock and a 16" gas piston and a 20-24" gas piston system? Where would a good starting point be?

Thanks


ETA: This may be a good candidate for a sticky.

[Daemonbane]

I'm ordering a BCM 20" upper this evening and I was wondering if I should use my original carbine buffer & spring or use an H2 buffer & spring I ordered from BCusa that I planned on trying out.

[BufordTJustice]

Wow this thread has been around a while. I'll keep it going with another noob question.

It seems that most of the talk in this thread is concerning DI systems and not really anything about piston systems. I'm gathering info on some builds I'm starting, and was wondering what to use for buffers and springs in a carbine stock and a 16" gas piston and a 20-24" gas piston system? Where would a good starting point be?

Thanks


ETA: This may be a good candidate for a sticky.

From the CMMG piston gun I've shot, I'd say that a starting point would be the H-Buffer with a standard power Chrome Silicon Buffer spring. If that works, maybe consider a sprinco XP buffer spring or a Tubbs flat wire buffer spring. If your gun can function with an XP buffer spring and H buffer, I would go for an H2 or a Spike's Tactical ST-T2 (also offered by PWS) and see if the rifle will lock-back when empty using the heavier buffers. You want to be as heavy as possible without sacrificing reliability. I had everybody telling me to 'not bother' using a heavier buffer or XP flat wire CS buffer spring....that a 16" middy didn't need it....a 16" middy didn't owuldn't run with it, etc etc etc. Well the naysayers were wrong...and now I've got a super smooth shooter that locks back on empty using .223 ammo even when dirty (300 rounds through it). The point is: find what works for you and be willing to experiment. I can only recommend chrome silicon springs (i.e. CS) as they take very little set over their lifetime...and their lifetime is commonly observed to be in the 20K-50K round range with only a single digit variation in spring strength. Regular stainless buffer springs provide noticeably reduced pressure by 3K rounds (sometimes less) and become unreliable after about 5 or 6K. Ask Pat rogers about that. ;)

I have a BCM 16" middy with a M16 bolt carrier, Tubbs Flat wire buffer spring, and Spike's ST-T2 buffer and my rifle eats everything (even cheap wally world .223 practice ammo). My guns shoots exceptionally smoothly....feels like a smaller caliber than my buddy's CMMG piston gun (or another's CMMG M4 clone).

[RAM Engineer]

I would like to nominate this thread for sticky status in the AR Technical Discussion subforum.

[rsilvers]

It is the job of the rifle maker to ship with the correct buffer. That being said, probably few do. I recommend using whichever buffer gives 800rpm with NATO ammo and a normal spring. True, not everyone has access to a FA lower for testing - all the more reason why the rifle maker should do this as part of their testing and selection process.

AAC 300 AAC Blackout 9 inch uppers are set up for H2 buffers. The 16 inch are designed around H buffers.

[RE4]

From the CMMG piston gun I've shot, I'd say that a starting point would be the H-Buffer with a standard power Chrome Silicon Buffer spring. If that works, maybe consider a sprinco XP buffer spring or a Tubbs flat wire buffer spring. If your gun can function with an XP buffer spring and H buffer, I would go for an H2 or a Spike's Tactical ST-T2 (also offered by PWS) and see if the rifle will lock-back when empty using the heavier buffers. You want to be as heavy as possible without sacrificing reliability. I had everybody telling me to 'not bother' using a heavier buffer or XP flat wire CS buffer spring....that a 16" middy didn't need it....a 16" middy didn't owuldn't run with it, etc etc etc. Well the naysayers were wrong...and now I've got a super smooth shooter that locks back on empty using .223 ammo even when dirty (300 rounds through it). The point is: find what works for you and be willing to experiment. I can only recommend chrome silicon springs (i.e. CS) as they take very little set over their lifetime...and their lifetime is commonly observed to be in the 20K-50K round range with only a single digit variation in spring strength. Regular stainless buffer springs provide noticeably reduced pressure by 3K rounds (sometimes less) and become unreliable after about 5 or 6K. Ask Pat rogers about that. ;)

I have a BCM 16" middy with a M16 bolt carrier, Tubbs Flat wire buffer spring, and Spike's ST-T2 buffer and my rifle eats everything (even cheap wally world .223 practice ammo). My guns shoots exceptionally smoothly....feels like a smaller caliber than my buddy's CMMG piston gun (or another's CMMG M4 clone).

Get a JP adjustable gas black and be done with it- quickly and more cheaply. My SW MP15 was seriously over gased.

[rsilvers]

My SW MP15 was seriously over gased.

If it was over-gassed, maybe use the next buffer or two up? H2, H3? Seems better than using an aluminum gas block with a set screw.

For me, over-gasssed is defined at a cyclic rate over 825 rpm without a silencer and over 950 rpm with one. I have the feeling a lot of guns thought to be over-gassed are really not.

[buzzman003]

So did we figure out what over gassed is? Is it a rate of fire or a test that includes the clock positions?

In summary, my cheap DPMS flat top oracle, needs an H buffer and not the standard Car buffer.

[rsilvers]

I would define it as - with a full auto lower, the cyclic rate should not exceed 950 rpm.

But how far and what direction the brass is thrown is a good clue.

[RE4]

So did we figure out what over gassed is? Is it a rate of fire or a test that includes the clock positions?

In summary, my cheap DPMS flat top oracle, needs an H buffer and not the standard Car buffer.


I didn't figure out that it was over based until I installed an adjustable JP gas block. I closed the gas port screw on my block and started to open it up by quarter turns. The rifle was cycling the ammo and locking back with only a 1/2 turn out ! Just in case to be able cycle weaker ammo (I reload) I opened it another 1/2 turn.


I did this with a carbine buffer that I took the weights out of. The recoil is non existent and the brass that ejects falls out undamaged a couple feet away.

[ra2bach]

So did we figure out what over gassed is? Is it a rate of fire or a test that includes the clock positions?

In summary, my cheap DPMS flat top oracle, needs an H buffer and not the standard Car buffer.

I assume you mean ejection pattern when you say "clock positions"? understand that many factors affect ejection pattern so it is not a reliable indicator.

overgassed (or not) is determined by cyclic rate and nothing else. this changes with gas port diameter, the power of ammo used and buffer/spring rate.

based on previous results, I would say your DPMS would be very safe with a H2 buffer and mild .223 spec ammo. if you're the experimenting kind, since you already have a CAR buffer, get an H3 buffer and pull the weights to mix and match the tungsten with steel weights to get CAR, H, H2 and H3 weights.