What buffer going from mid-length to 14.5" carbine?

[Doc Safari]

I see a lot of threads concerning what buffer for a 14.5" mid-length, but so far I haven't found one on my particular situation.

I purchased a complete BCM mid-length weapon last spring. The rifle has an "H" buffer installed.

The GF decided that was "her" gun when we're at the range and wanted a carbine 14.5" pencil barrel with permanently pinned FH. Done deal. Got it from BCM this morning with BCG headspaced to it and a BCM Gunfighter charging handle.

Now it's got me thinking.

Should I have replaced the buffer also, or should I reasonably expect the 14.5" carbine upper to cycle properly with the "H" buffer as it came from the factory with the lower? I don't know what buffer spring is installed: it's whatever BCM installs with their mid-lengths at the factory.

We plan to shoot mostly PMC .223 through it, since I have more of that ammo than any other, but of course I want it to be reliable with 5.56 ammo as well.

Should I hurry up and order a carbine buffer? Will the "H" buffer probably work? Is this going to be a trial and error thing until I find the right combination?

[PRGGodfather]

You should be just fine. An H in a 14.5 middy would much like running an H2 on a carbine, which many of us do without problems. It should be a very soft shooter.

[Doc Safari]

You should be just fine. An H in a 14.5 middy would much like running an H2 on a carbine, which many of us without problems. It should be a very soft shooter.

Mine is not a mid-length 14.5" though...it's a carbine upper...or did I misread your response?

:D

[buckshot1220]

The H buffer will be good to go with both.

[Todd.K]

H for a correct ported 14.5" carbine like yours.

[Doc Safari]

Thanks for the responses guys.

Is the mid-length 16" roughly equivalent in gas pressure/dwell time, (or whatever term I'm searching for) as the 14.5" carbine, and that's why some people prefer the mid-length for a barrel with a non-permanent FH?

(I thought I had read that in a thread months ago, but maybe I'm thinking of something else.) :confused:

[markm]

According to some of RSlivers measurements, the carbine will be optimal and closest to a rifle buffer system with an H2.

This is assuming you're running a Mil spec spring and not some rainbow homo spring.;)

[Doc Safari]

Everything is all BCM factory.

So, what are you saying? I should get an H2 buffer?

I'm wanting maximum reliability.

Most responses on this thread seem to indicate the H buffer is the correct one.

How will the H2 buffer help?

[markm]

Well... the fact that you're going to run PMC might be a reason to just go H buffer. Reliability will be better... it's just that the gun will run a little harder.

Anything 14.5 or shorter gets an H2, H3, A5, or Rifle buffer system in my arsenal. (except for the middy)

[Doc Safari]

Well... the fact that you're going to run PMC might be a reason to just go H buffer. Reliability will be better... it's just that the gun will run a little harder.

Anything 14.5 or shorter gets an H2, H3, A5, or Rifle buffer system in my arsenal. (except for the middy)

Okay, that answers my question, thanks.

Your post makes me think that I should at least try out an H2 buffer if I start running mostly full power 5.56 ammo. Good to know.

[Doc Safari]

Just for kicks I e-mailed Bravo Company. They said to use the standard carbine buffer. Not that the H buffer won't work, according to their response, just that the carbine buffer may run better, and that the lighter ammo will have an effect also.

Interesting the range of responses I've gotten to this thread.

I may order up a carbine buffer since it's only eleven bucks, but it sure indicates that some experimentation cannot be avoided.

In a nutshell: there is no right or wrong apparently--just fine tuning.

[Iraqgunz]

I won't attempt to read Pauls' mind, but my guess is that he was playing it safe and giving you an across the board answer.

Since many people are shooting a variety of ammo types one has to be cautious.

I did quite a bit of testing with markm's 14.5" midlength and we ran all kinds of buffers to include the H3 and I believe an A5.

In the end, whatever buffer you use, make sure that all of the ammo you use, will cycle the weapon.


Just for kicks I e-mailed Bravo Company. They said to use the standard carbine buffer. Not that the H buffer won't work, according to their response, just that the carbine buffer may run better, and that the lighter ammo will have an effect also.

Interesting the range of responses I've gotten to this thread.

I may order up a carbine buffer since it's only eleven bucks, but it sure indicates that some experimentation cannot be avoided.

In a nutshell: there is no right or wrong apparently--just fine tuning.

[Doc Safari]

I won't attempt to read Pauls' mind, but my guess is that he was playing it safe and giving you an across the board answer.

Since many people are shooting a variety of ammo types one has to be cautious.


I kind of took it the same way. They also know that if the gun doesn't cycle they may get a warranty complaint when really the gun is fine if you understand the differences in ammo power. I'm guessing the standard carbine buffer is what Paul would consider will run "wide open" with the most ammo types. It's just that the gun will suffer more wear and tear with hotter loads than if an "H" buffer were used, if I understand the whole buffer changing concept.

This is where I was surprised as to which one Paul would recommend: all of my BCM guns, whether 16" M4 or 16" mid-length, came with the "H" buffer. I was a bit surprised that he recommended the carbine buffer. I even e-mailed back to get him to clarify and he confirmed. "Plain Jane" carbine buffer was his recommendation.

IIRC most people recommend running with the "heaviest buffer that will allow the action to cycle," correct?

EDITED TO ADD: The standard USGI 14.5" M4 uses an "H" buffer, right?

[rsilvers]

Whichever buffer results in a cyclic rate closest to 800-825 rpm when on a FA lower.

Seriously - that is the only answer. No one can tell you which buffer is best without this test. If it were me, I would first put in an H2 buffer, then adjust the gas port to be the correct cyclic rate.

In leu of all this - you can look what what ejects to same distance as rifles which are known to be set up correctly. I am not sure how far that is though - I never correlated ejection patterns to cyclic rates. It is not a perfect way to go about it.

[rsilvers]

IIRC most people recommend running with the "heaviest buffer that will allow the action to cycle," correct?

Not sure what most people recommend, but that is not a good thing to do. There are ARs that cycle at 550 rpm, but they are not as reliable across a broad range of conditions and level of dirtiness as ARs that cycle at 800 rpm.

[PRGGodfather]

Mine is not a mid-length 14.5" though...it's a carbine upper...or did I misread your response?

:D

Nope! I misread your post. Either way, you're fine, though. We run Hs on middies, and H2s in our carbines as standard fare.

[Iraqgunz]

And what if you don't own full auto and don't have access to one?


Whichever buffer results in a cyclic rate closest to 800-825 rpm when on a FA lower.

Seriously - that is the only answer. No one can tell you which buffer is best without this test. If it were me, I would first put in an H2 buffer, then adjust the gas port to be the correct cyclic rate.

In leu of all this - you can look what what ejects to same distance as rifles which are known to be set up correctly. I am not sure how far that is though - I never correlated ejection patterns to cyclic rates. It is not a perfect way to go about it.

[Iraqgunz]

IIRC Colt was shipping new military contract M4's with the H2 buffer. Although I cannot be 100% sure, I believe that was the case.


I kind of took it the same way. They also know that if the gun doesn't cycle they may get a warranty complaint when really the gun is fine if you understand the differences in ammo power. I'm guessing the standard carbine buffer is what Paul would consider will run "wide open" with the most ammo types. It's just that the gun will suffer more wear and tear with hotter loads than if an "H" buffer were used, if I understand the whole buffer changing concept.

This is where I was surprised as to which one Paul would recommend: all of my BCM guns, whether 16" M4 or 16" mid-length, came with the "H" buffer. I was a bit surprised that he recommended the carbine buffer. I even e-mailed back to get him to clarify and he confirmed. "Plain Jane" carbine buffer was his recommendation.

IIRC most people recommend running with the "heaviest buffer that will allow the action to cycle," correct?

EDITED TO ADD: The standard USGI 14.5" M4 uses an "H" buffer, right?

[Doc Safari]

Well, then I guess it's experimentin' time.

If weather and time allow, I'll try it out this weekend.

Everything is pointing to "split the difference and start with the H buffer." I have some PMC Bronze .223 and I believe some Winchester white box 5.56. I'll have to dig around and see.

I've got the standard carbine buffer ordered from BCM, so if it arrives Priority Mail before I have time to go to the range, I'll leave the "H" buffer installed in the weapon and have the carbine buffer handy.

Probably I will not order an H2 buffer unless someone convinces me it's really necessary. I'm somewhat confused as to what advantage it offers over the H buffer except in reducing wear and tear with hotter ammo. As long as the H buffer cycles reliably with the widest range of ammo, it's the one I'll keep in the gun.

I'll try to report my results over 100 rounds or so as I have a chance to go to the range, which may or may not be this weekend depending on what ranch business I have to do.

[TacMedic556]

Hey Doc,

I highly respect the opinion of Mike Pannone. I recommend the following three articles:

http://www.defensereview.com/m4m4a1-carbine-reliability-issues-why-they-occur-and-why-theyre-our-fault/

http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/

http://www.defensereview.com/m4m4a1-carbine-reliability-issues-part-ii-diagnosing-the-root-cause/

Malfunctions: http://www.defensereview.com/an-operators-view-of-m4m4a1-carbine-and-ar-15-carbine-malfunctions/

I spoke with him recently and he has been moving towards heavier reciprocating weight (like H2) with "standard" springs or a "blue". As always function test for performance and reliability. Read his articles though. Good stuff.

I have a Colt Carbine with an H and Blue, and a 14.5 BCM middy with an H and a standard "white" spring.

I have run an H2 in the carbine and it runs fine with M193 and 855.

[Doc Safari]

Hey Doc,

I highly respect the opinion of Mike Pannone. I recommend the following three articles:

http://www.defensereview.com/m4m4a1-carbine-reliability-issues-why-they-occur-and-why-theyre-our-fault/

http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/

http://www.defensereview.com/m4m4a1-carbine-reliability-issues-part-ii-diagnosing-the-root-cause/

Malfunctions: http://www.defensereview.com/an-operators-view-of-m4m4a1-carbine-and-ar-15-carbine-malfunctions/

I spoke with him recently and he has been moving towards heavier reciprocating weight (like H2) with "standard" springs or a "blue". As always function test for performance and reliability. Read his articles though. Good stuff.


First of all, I don't want to dismiss the articles out of hand. The man has clearly amassed a lot of experience in this subject, and I believe he knows what he's talking about. (Yes, I took Evelyn Wood's Speed Reading Course and I really did and can read and comprehend the articles that fast). It's clear that there is more than one way to enhance an M4's reliability by tweaking different components. Given.

I'm afraid we're beginning to see nothing but trees and have forgotten the forest.

To simplify things to avoid the "won't go mad trying all of this" syndrome:

I want to take what is now a BCM 14.5" carbine, which started as a bone stock 16" BCM mid-length, and make the minimum number of changes to make it as reliable as a bone stock 16" BCM carbine. I want it to be reliable with 5.56 ammo, and reasonably reliable with .223 (allowing for the fact that Wolf and others may be too underpowered).

I've not had a problem shooting PMC Bronze .223 in the same carbine as 5.56 XM193, so I consider it adequately powerful to cycle reliably.

All of my 16" BCM carbines came with an "H" buffer.

The former 16" mid-length, which is now the 14.5" carbine, also came with an "H" buffer.

I do not know what recoil spring BCM installed in each rifle, but I thought Paul at BCM would have mentioned it if relevant when I e-mailed them as to what buffer to use.

So, to summarize...the bottom line is that a change in buffer appears to meet the criteria for "minimum number of changes" to make the 14.5 as reliable as the 16 middy.

And....if so...what buffer would that be?

[Todd.K]

I want it to be reliable with 5.56 ammo, and reasonably reliable with .223 (allowing for the fact that Wolf and others may be too underpowered).

You should be fine with the H buffer.

[Doc Safari]

You will never go wrong with the H buffer in a Carbine though. Hope some of it helped. Again, this is not my opinion, its just what others much more experienced than me have come up with. take care.

Between you and Todd.K and the others who've said as much, I will stick with the plan to have the "H" installed for my first test and I'll keep the carbine buffer on standby.

You've presented some good info, especially for people who do a lot of tinkering or participating in harsh firing schedules to quote a term.

I may try some of these other combinations later but for now I'm content to get the gun working for everyday use.

[ra2bach]

Well, then I guess it's experimentin' time.

If weather and time allow, I'll try it out this weekend.

Everything is pointing to "split the difference and start with the H buffer." I have some PMC Bronze .223 and I believe some Winchester white box 5.56. I'll have to dig around and see.

I've got the standard carbine buffer ordered from BCM, so if it arrives Priority Mail before I have time to go to the range, I'll leave the "H" buffer installed in the weapon and have the carbine buffer handy.

Probably I will not order an H2 buffer unless someone convinces me it's really necessary. I'm somewhat confused as to what advantage it offers over the H buffer except in reducing wear and tear with hotter ammo. As long as the H buffer cycles reliably with the widest range of ammo, it's the one I'll keep in the gun.

I'll try to report my results over 100 rounds or so as I have a chance to go to the range, which may or may not be this weekend depending on what ranch business I have to do.

I don't have access to cyclic rates but dwell times on a 16" midlength and 14.5" carbine are practically identical as a 20" rifle.

this is considered to be the sweet spot. I would use an H, H2, or an A5 buffer in a midlength unless I was having problems and then go down one in weight till the symptoms disappeared. same for a 14.5 carbine....

[Doc Safari]

THE TEST

With a Bravo Company carry handle rear sight, I quickly learned the gun was sighted in "close enough for government work" at 50 yards without even having to touch the sights. This carbine is one accurate sumbitch at least with the Coke cans I was blasting. Since I was more interested in reliability for this test, I wasn't worried about getting the gun perfectly sighted in.

For control, I decided to use 100 rounds of PMC Bronze 55-grain .223 from a known lot that has been 100% reliable over 500 rounds in my 16" Carbine.

I also had 40 rounds of Winchester white box 5.56 in 55-grain.

I lubed the BCG like I always do. I decided to use a known reliable magazine (Bravo Company mag with MagPul follower) to eliminate that as a cause of potential malfunctions.

I also decided to load fresh magazines by locking the bolt back manually and tripping the bolt catch to load the first round.

For the first 20 rounds of PMC I loaded two rounds in the mag and fired them to test cycling and the bolt locking back. Test passed. Ejection was at about 3 o'clock.

The 40 rounds of 5.56 fired flawlessly. Recoil was noticeably snappier than with .223.


Now the bad news.

Although both ammo types cycled just fine, I had two noticeably spectacular failures to extract with the PMC. One empty case had to be gently tapped out of the chamber with an old AK cleaning rod. The other empty case fell out when I got the BCG rearward and the mag out of the rifle. Both failures to extract tended to happen within the first five rounds of the magazine.

Since this was a lot of PMC known to be reliable in my 16" carbine, I'm trying to figure out what would have caused two extraction failures in 100 rounds with this 14.5" carbine. Extraction of the Winchester 5.56 was flawless, although I wish I had 100 rounds of it to make the chances of malfunction more equal.

My first thought is that maybe I need to switch to an H2 buffer.

Is the extractor trying to rip the case out of the chamber when it's still expanded?

Is there something potentially wrong with the extractor itself?

I eyeballed the extractor, chamber, and locking lugs on both the receiver extension and bolt for any obvious flaws and didn't see any.

What do you think?

[TacMedic556]

This is with a new BCM BCG with BCM extractor spring? It could be an extraction spring issue if the tension is not enough. Make sure it is installed properly over the black insert, large opening of spring pushed onto black insert and into the "cup" on extractor. Should be a snap. If you do not have a good spring try with a Crane "O" ring. I am not a fan of "o" rings in my bolt (another issue) but if your spring is weak do it. A nice 5 coil spring from Sprinco or BCM should work fine without the "o" ring.

If it is a BCM BCG and the extractor spring is good it could be your ammunition. I'm sure Iraqguns or another more knowleadgable expert will be able to offer you more information. Let us know what you find out.

[Doc Safari]

This is with a new BCM BCG with BCM extractor spring?

Yes, and the O-ring still sits in the packaging. :D

Waters: Meet Mud.

On the theory that it might be too light a buffer I headed back out to the range with about 75 more rounds of the same lot of PMC .223.

This time I installed the standard carbine buffer on the theory that an even lighter buffer would cause even more of the same malfunction. If I got a couple of failures to extract with PMC ammo and the "H" buffer then the lighter carbine buffer should lead to even more failures to extract, correct?


Recoil of course felt noticeably stouter with the standard carbine buffer.

To my surprise I did not have even one malfunction this time.

Could it be that Bravo Company's advice was correct and the carbine buffer would be more reliable with the lighter .223?

Was the heavier "H" buffer maybe causing the bolt carrier to drag on the ammo in the magazine just enough to make the extractor a little sluggish in pulling a sticky round out of the chamber?

Could it be the gun needed a little break-in?

I cannot believe it is the ammo: it would be an incredible coincidence for the failures to extract to have happened just within 200 rounds of today's session, when I just happened to be shooting the 14.5" carbine.

I even took my 16" back out after my first post on this forum today because I needed to fine tune the sighting of my Aimpoint T1 on that carbine. Not one malfunction with the same lot of PMC and that rifle either.

So I am stumped.

I wish I had a few more boxes of different brands and powers of ammo. This test could go on all day. :jester:

I love this rifle. It shoots to point of aim and more accurately than any rifle I've owned in many moons.

So, my conclusion: maybe BCM was correct in advising me to install the standard carbine buffer?

I'd love to hear everyone's thoughts on this.

[Doc Safari]

It could be an extraction spring issue if the tension is not enough. Make sure it is installed properly over the black insert, large opening of spring pushed onto black insert and into the "cup" on extractor.

All good to go from what I can tell. Proper black insert, spring seated properly, extractor does not look bent, everything had plenty of lube (still). I would even say the extractor spring has plenty of tension in my Troglodyte opinion because it took considerable thumb pressure to hold the extractor in place and re-insert the extractor pin.



If it is a BCM BCG and the extractor spring is good it could be your ammunition. I'm sure Iraqguns or another more knowleadgable expert will be able to offer you more information. Let us know what you find out.

Although I can't rule it out, it would be an incredible coincidence for two rounds to be bad in the over 200 I fired today, and those rounds just happened to occur while firing the 14.5" carbine and within a couple of magazines of each other. Remember also that this lot of ammo I consider "vetted" because it's from a case I've been firing flawlessly in my 16" BCM carbine for months.

I might blame the D & H mag except that it's one I knew was good.

After installing the standard carbine buffer, I actually "cheated" and used two untried D & H mags because they were already loaded.

Once again, not a single malfunction on that last trip to the range with the same ammo.

So? Ammo? Could be a couple of bad rounds but once again what an incredible coincidence.

I won't consider this carbine properly vetted until it shoots around 500 rounds without repeating the malfunction, and with a variety of different types of ammo.

But I lean toward thinking Paul at BCM was correct and the change in buffer cured it.

If I'm looking at it wrong, feel free to speak up.
Thoughts?

[TacMedic556]

I might blame the D & H mag except that it's one I knew was good.

After installing the standard carbine buffer, I actually "cheated" and used two untried D & H mags because they were already loaded.

Once again, not a single malfunction on that last trip to the range with the same ammo.

So? Ammo? Could be a couple of bad rounds but once again what an incredible coincidence.

If I'm looking at it wrong, feel free to speak up.
Thoughts?


From reading others such as Pannone, 80% of Malfs that occur are magazine related, so that could be an issue. 55 PMC would be ever so light enough to cause short stroking with that H buffer. So again it could be ammunition related, which is another common cause of malfs.

Running H weight buffers has become an accepted minimum weight for properly gassed carbines with 14.5" barrels and carbine gas systems. Heck, others run H2 and H3 buffers in carbines identical to yours.

Have you tried shooting it unshouldered and unsupported? I hate to say, "from the hip". Shooting it unshouldered at your side with a light grip with only one round and an empty mag will help determine if your bolt is locking back properly.

Try this same test with some M193 or M855 ammunition. I personally choose to run a minimum of H buffer and standard powered carbine spring in my Colts. With my 14.5 Mid length BCM (less gas pressure than your carbine) I run a H weight and a standard "white" sprinco spring.

My shooting partner, dad has run a "Blue" Sprinco (15% more tension) spring with an H2 buffer in his 14.5 middy BCM and did the test I mention above with several magazines and had lock back every time, and never has had a malf once.

Try a similar load perhaps, like the 55 grain HSM (hunting shack-orange box). See what happens?

Try to isolate that magazine you had the malfs with too. I number all my magazines and keep track of any malf that occurs with it. If you do not get this malf with any other magazines and your gun runs with your ammunition, even including passing the unshouldered lock back test, I would vote you keep the H buffer in it.

The military issues the 14.5 carbines with H buffers, BCM ships all their guns with H buffers (as do most manufacturers including LMT and Noveske). Every Colt 6933 in our SWAT locker has an H buffer, and was issued with them from Colt.

It is probably, a) Magazine related, b) ammunition related, c) parts related, or d) user error.

Your parts should be perfect (BCM), you seem to know what you are doing, so that takes away c) and d). That leaves us with a) and b). I left out maintanance related because you already said that it is lubed and wet. Sorry I wrote so much. Keep us posted.

[Doc Safari]

For the first magazine with the "H" buffer installed, I fired it from the hip a few times so I could see the ejection angle. I believe the very first two rounds were fired from the hip so I could watch it lock back on an empty mag, and thereafter I fired it from the shoulder with maybe an occasional round fired from the hip to see if the 5.56 and .223 ejected at the same angle.

I do know those D & H mags are not up to the same standard as USGI mags, but the only malf I've had with one before today was in chambering the first round from a fresh mag in my 16" carbine (failure to feed with the bullet nose getting hung up on either the feed ramps or the mag edge).

The mag that saw the two malfunctions was a mag I've trusted before. I would say that mag had fired at least 100-150 rounds through it before today without issue.

So, I can't discount the possibility that it's mag related.

I'm not trying to "insist" on my point of view, but I keep going back to Bravo Company recommending the standard carbine buffer. Like Iraqgunz says (and I personally believed) Paul recommended that one as a "catch-all" to make sure it shoots even with crappy underpowerd Wolf and Tulammo, but maybe that PMC is just a notch above that category too. Maybe my 16" is overgassed just enough that it hasn't had that failure...yet.

And no, I don't have any problem with long responses. I don't have all the answers either and I like to see people reason out their responses rather than just type out "it's gotta be this or that" with no explanation.



:cool:

[Doc Safari]

Since no one has offered any more replies, I hope nobody minds if I start using this thread as kind of a personal notebook.

Here's a thread where someone in a similar situation to mine apparently fixed it with a CAR buffer:

https://www.m4carbine.net/showthread.php?t=86251


Although his rifle was a mid-length, aren't the pressure curves for a mid-length and a 14.5" carbine the same (hence some people prefer the mid-length)? His problem was also apparently a lot worse than mine. He also had double feeds of live rounds. Interesting that the CAR buffer seemed to clear it all up, though.

Remembering back to when I first purchased my complete rifle as a 16" midlength, I remember only shooting 5.56 in it because of Bravo's disclaimer about their being more reliable with full power ammo. I wonder If would have experienced the same malfs with PMC and the midlength upper?

I've also done a search on "PMC stuck case" here and Google to see if that could be an ongoing problem. I haven't really found much there, unless it was one post buried in an epic thread that I just skimmed.

I'm not really sure what further tests I could devise, except to shoot up the remaining rounds in this lot of PMC bronze and see if the gun remains "cured".

I'm somewhat averse to blowing the rest of a case of ammo just for testing purposes unless I plan to shoot for practice anyway.

[Iraqgunz]

Doc,

I think you are way overthinking this. Simply shoot the weapon with the buffer that allows for reliable function.

Ammo should always be taken into account. Even the best manufacturer can churn out bad stuff.

[nml]

I think you are way overthinking this. Simply shoot the weapon with the buffer that allows for reliable function.+1 +1 +1 ... I wish we hadn't gone past "You should be fine with the H buffer."

[Doc Safari]

Doc,

I think you are way overthinking this.

Just trying to run an obsession into the ground--LOL. :alcoholic:

This is part of my learning curve. I was starting to enjoy the experimentation. :D

At some point I will run different types of ammo through it, but since I have a buttload of PMC I wanted to get the gun running reliably since the GF will be shooting it next time we go to the range.

Having run another half dozen flawless mags of PMC through it this past weekend, I'm satisfied with: carbine buffer for weak, cheap ammo/H buffer or heavier for full power 5.56. This also seems to agree with the manufacturer's recommendations.

Obsession finished. ;)

:D