View Full Version : What buffer are you running with your BCM 11.5" upper?
Rotorhead84
12-16-15, 18:24
Can't really find anything via a search of the internet for BCM nfa barrels paired with buffers. I see a lot of generic answers out there of "I run buffer "x" in my 11.5 or 10.5" or whatever. But the brand is usually left off the answer and I know that gas port sizes vary. I've read a lot of good things about BCM barrels and specifically their 11.5's and I'm wanting to pick one up for my first SBR build.
I'm not sure if I'm gonna go with their standard 11.5 or their CHF 11.5 but I am (perhaps foolishly) assuming that both use the same gas port size.
All that out of the way, what weight buffer are you using with your BCM 11.5? Carbine buffer spring of course...
jackblack73
12-16-15, 18:32
I use a BCM H2 with carbine springs. Runs Wolf fine.
https://www.m4carbine.net/showthread.php?53278-Buffer-weight-for-11-5-quot-SBR
https://www.m4carbine.net/showthread.php?166689-Just-ordered-a-BCM-11-5-upper-what-is-the-best-buffer-to-use
https://www.m4carbine.net/showthread.php?167491-Buffer-for-11-5-inch-SBR
A5H3.
Yep, I agree, the A5 is the way to go. The OP asking about a carbine RE though.
H2 = carbine RE
A5H3 = A5 RE
Rotorhead84
12-16-15, 19:03
A5H3.
That looks like a rifle buffer?
That looks like a rifle buffer?
It's a buffer for the A5 system.
https://www.m4carbine.net/showthread.php?164034-The-VLTOR-A5-thread-what-doesn-t-it-work-with
All my new builds get the A5 RE.
The standard A5H2 works great with most everything.
Rotorhead84
12-16-15, 19:53
All my new builds get the A5 RE.
The standard A5H2 works great with most everything.
Just googled it. Interesting idea for sure. Worth considering. However I was planning on running a UBR on this gun, so unfortunately I'm stuck with carbine buffers and springs.
domestique
12-16-15, 20:18
H2 works well with XM193 and a SOCOM556-RC.
Mine ran fine with an H2, I had to go to an H3 when I started to run it suppressed.
Mine ran fine with an H2, I had to go to an H3 when I started to run it suppressed.
What happened that made you have to switch to an H3 when running suppressed?
I ask because I'm awaiting for my can to get out of NFA jail.
I'm currently running a BCM 11.5 ELW with H2 buffer and carbine spring and it's been completely reliable.
What happened that made you have to switch to an H3 when running suppressed?
I ask because I'm awaiting for my can to get out of NFA jail.
I'm currently running a BCM 11.5 ELW with H2 buffer and carbine spring and it's been completely reliable.
When I ran it with a 30 cal can, I had no issue with an H2. When I would run it with a AAC Mini-4 I would get a handful of bolt over base and FTEs. Switched to an H3 and no more issues in about 1200 rounds.
When I ran it with a 30 cal can, I had no issue with an H2. When I would run it with a AAC Mini-4 I would get a handful of bolt over base and FTEs. Switched to an H3 and no more issues in about 1200 rounds.
Interesting...thanks for the quick reply. I've got an H3 in the tool box just in case.
Piggy backing this thread, what about with an adjustable gas block w/ suppressor? Stick with the H2 as a base line?
Not really an answer to the OP's question, but wouldn't you run the heaviest buffer that will allow your rifle to function reliably with run of the mill 223Rem ammo? This way you'll know it will run with 5.56x45, but you won't be ejecting the brass any harder than you have to? I do realize that the OP is trying to get an idea of where to start, but it would also be nice to know where it's best to end up.
Although I can't really go into specifics, there can be a trend of use for reliable functions for different applications of the 11.5" AR type 5.56 systems that may, or may not use a can. Generally, the better options work well in that band for use. Different barrels, cans, ammunition, action systems, etc may reflect more positive or negative in others for use.
So, let's say a BCM 11.5" 5.56 barrel is selected, it has it's own attributes. What is the ammunition range, 5.56 port pressure only, or anything including steel case .223? That can make a big difference.
Limiting the system to a carbine type action gives a narrower band of operation than of a more rifle like or A5 action type. I can understand a basic retro fit, that doesn't mean it could operate in function overall as well.
Adding a can is another variable, no two cans change operation the same way.
Another possible change is in the carrier, it is very possible to make a change and shift preferable results?
So, you get a BCM barrel and want to know what buffer to use? That question has an added request for a carbine action that limits choices.
Some crap, but available ammo would need a low buffer mass close to the 3 ounce to run, it would hyper cycle with this in many plausible combinations. If good 5.56 port ammo is run, a carbine H2 or H3 could be better. With a possible unknown can, it would be more like a H2 without a can with 5.56, and a H3 with 5.56 and most cans.
There are other possible combinations that could require more or less mass than normal, but how can a general consensus be made without knowing what they may be?
domestique
12-17-15, 18:06
Although I can't really go into specifics, there can be a trend of use for reliable functions for different applications of the 11.5" AR type 5.56 systems that may, or may not use a can. Generally, the better options work well in that band for use. Different barrels, cans, ammunition, action systems, etc may reflect more positive or negative in others for use.
So, let's say a BCM 11.5" 5.56 barrel is selected, it has it's own attributes. What is the ammunition range, 5.56 port pressure only, or anything including steel case .223? That can make a big difference.
Limiting the system to a carbine type action gives a narrower band of operation than of a more rifle like or A5 action type. I can understand a basic retro fit, that doesn't mean it could operate in function overall as well.
Adding a can is another variable, no two cans change operation the same way.
Another possible change is in the carrier, it is very possible to make a change and shift preferable results?
So, you get a BCM barrel and want to know what buffer to use? That question has an added request for a carbine action that limits choices.
Some crap, but available ammo would need a low buffer mass close to the 3 ounce to run, it would hyper cycle with this in many plausible combinations. If good 5.56 port ammo is run, a carbine H2 or H3 could be better. With a possible unknown can, it would be more like a H2 without a can with 5.56, and a H3 with 5.56 and most cans.
There are other possible combinations that could require more or less mass than normal, but how can a general consensus be made without knowing what they may be?
Holy crap Tom, did you stay at a Holiday Inn last night? ;)
To paraphrase: every rifle setup is different (barrel port, ammo, suppressor blowback etc.). It's best to run your setup and see how it ejects and work from there.
In general, a suppressed AR with a decent gas port will run a H2 or H3 depending on which ammo and how much backpressure your suppressor adds.
I wish it was that easy, but there's variables that work better than others in a range of use.
There are commercially available products available now that can support a wider range in function when compared to some traditional components. That doesn't mean the others are bad, they just operate differently.
In the OP's case, choices could be had that work with improvement over others.
Want to get bored and burned out? Get assigned into a focus group about some of these specifics.
With unknown variables, you can not have absolute conclusions. Knowing that, there are some combinations that are known to have a wider range in use. That does not mean the OP has that requirement.
firefighter37
12-18-15, 12:10
To answer the original question, I run an A5H4, but have also ran an H2 with good results. This is both suppressed and unsuppressed.
Mine suppressed with h2 and adjustable gas block
Sent from my iPhone using Tapatalk
One of the things that always frustrated me was the many variable encountered in the commercial market.
A contract market has (usually) a finer set of defined goals. Company "X,Y, and Z" may work pretty good.
Company X meets the goals well with a price point of "A".
Company Y is close to the goals with a lower price point than "A".
Company Z far exceeds the goals with a much higher price point than "A".
Who gets awarded?
Big ARMY buys X and Y, small ARMY buys X and Z.
Company focus determines who they want to cater to.
None are wrong in their actions.
Going into the commercial side with unknown variables, how do you make a general consumer prefer one to the other? What compromises are done?
What drives the contract market and what drives the commercial market are not mutually the same.
Rayrevolver
12-18-15, 20:00
Piggy backing this thread, what about with an adjustable gas block w/ suppressor? Stick with the H2 as a base line?
I was going to ask the same thing in my 11.5 middie thread. I have it set up, AGB + suppressor and running an A5H2. I also have an A5H4 laying around. I *think* the right answer is to setup and use the lighter buffer, but figured I would piggy back here too.
donlapalma
12-18-15, 20:41
I'm using an H2 and run 100% suppressed. I shoot mainly M193 and it has worked fine so far through 1,200 rounds.
The 11.5" 5.56 can be tricky, but there's many ways to skin that cat. Some options could be more preferable than others, just depending on what variables are proposed.
Some work is more or less fixed into the system. Hammer reset, proper over travel, feeding, and locking are easy to understand. What is less understood by most are the possible solutions to deal with the work in unlocking and extraction.
What possible combinations of gas port, available commercial components, and ammunition could result in a larger or more narrow operating band of function?
We want a wider band of function of use for a preferred setup. When using conventional concepts, there can be many plausible solutions. I do not prefer chamber and/or throat alterations, nor loose bores. I do not prefer the higher stresses and strains that require more work when compared to another system within the same confines for the same use to unlock and/or extract.
Within the confines of the current system, many options could be had. Choosing an option with a possible wider band of use/function is part of the goal.
An easy or easier possible solution is to look at the work involved. The carbine gas and carbine action could work together well with a simple H2 buffer. Does that mean that is the best solution? Maybe not?
The work involved with unlocking and extraction descends with time. A rapidly depressurizing barrel requires different amounts of work to operate at these different times. A wide or wider band of use may be had with some other options.
Let's say we keep the chamber short, no throating, in a tight bore. We want to delay unlocking/ extraction to minimize work and strains. How can we get closer to there with commercial parts? There can be some possible solutions.
If you look into the c
BCM 11.5 complete, H2 buffer, carbine spring, unsuppressed. Runs assorted GTG and garbage ammo.
Eurodriver
12-20-15, 16:05
BCM 11.5 complete, H2 Buffer, Carbine Spring, Suppressed. Runs assorted GTG and garbage ammo.
devilsdeeds
12-23-15, 01:39
I've been using an A5H5 in my 11.5 complete unsuppressed using xm193 with no issues.
My 11.5" BCM hasn't been run suppressed yet so keep that in mind, but if you order a factory BCM 11.5" SBR it will come with an H buffer installed. I run an H buffer in mine and it's worked flawlessly.
My 11.5" BCM runs both suppressed and unsuppressed with Spikes ST T2 just fine.
kaltesherz
12-25-15, 00:01
My 11.5 BCM upper runs on an A5H4 w/ green spring & LMT Enhanced carrier w/ Surefire SOCOM. Runs 100% both suppressed and not, very soft shooting.
Exactly the same set up I run with the exception of the suppressor.
My 11.5 BCM upper runs on an A5H4 w/ green spring & LMT Enhanced carrier w/ Surefire SOCOM. Runs 100% both suppressed and not, very soft shooting.
The addition of the LMT enhanced carrier with the rifle like A5 system has many potential positive attributes in function over the standard carrier with a carbine action in a 11.5" 5.56 AR platform.
I tend to prefer a porting that is more inline with the A5H2 with a Colt rifle action spring. If the system supports properly the A5H4 without a can, then you have reduced options if a can may be involved.
If it is gassed for a A5H2 with 5.56 ammo, non suppressed, you can step up or down as variables change. Lower buffer mass may be used with lower port pressure ammunition, like some .223. Higher buffer mass may be used with the addition of a can or other variables.
The LMT enhanced carrier with a rifle like or A5 action system seems to prefer more conservative porting to maximize gains when compared to a standard carrier with carbine type action system. The delay in time reduces the work load with this combination and does not need as much gas to drive the system to function properly.
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