View Full Version : Thinking about getting A5 buffer system w/ adjustable gas block...
BoringGuy45
08-29-16, 16:03
I have a standard M4 buffer tube coming in from BCM in a day or so, but apparently I've had my head up my ass and I'm just starting to look into possibly doing an A5 buffer system on the build instead. This will be for a 12.5" SBR that I'm planning on putting an SLR adjustable gas block on, as I'm planning on doing a lot of suppressed shooting. The question I have is: Does having one (adjustable block or A5 system) negate the need for the other in terms of stopping overgassing or lowering cycle rate, lessening the bolt bounce, etc? Or will both do different things?
Not the expert here but from my limited knowledge they are for different things. The A5 more so for slowing cycle rate to improve wear, recoil, etc. Whereas the adjustable gas block is for adjusting gas for shooting supressed and unsuppresed.
firefighter37
08-29-16, 16:48
They can both work in concert, but it may take some experimenting with buffer weights and gas port size to figure out what works best for you.
They can both work in concert, but it may take some experimenting with buffer weights and gas port size to figure out what works best for you.
I agree to a point. You can find a balance of port size for a 12.5" gas 5.56 AR that can work well without a can. Within that balance, you can run that same port with a can using additional reciprocating mass via the buffer.
I run these frequently. The actual port size and mass difference in the action just depends on the puzzle pieces presented. These can run really well, one of my favorite SBR 5.56 AR combinations.
I believe it is IG who has some good info on here about SBR's with A5's and running them supressed/unsuppressed. I would look into those posts. A lot to be learned in there.
No reason not to go a5 on a new build. Be warned, all your other lowers will grow a5 extensions too!!
Get the bcm 8pos or new magpul 10pos tubes. I suggest going with an a5h2 buffer and tuning your agb to the a5h2+can. That way you have the option of dropping to a5h0 buffer w the can off as Tom is suggesting.
You could tune to a lighter buffer, but I like to have a little extra weight in the action to keep reliability up when dirty or dry to really whack rounds out of the mag.
Without knowing what variables could be involved, there can be multiple scenarios. I would tend to choose variables that could lead towards a wider span of operation. This can be done by most with the A5H2 without a can and with the A5H4 with a can, both with some wiggle room for the variables. An A5H0 can run without a can, but the span in range can suffer compared to a more conventional A5H2 without a can.
Another model may be to gas it suppressed with the A5H4 with the can and reduce the action mass w/o a can to better suit the range in function via a reduced buffer mass. Be that an A5H3 or A5H1 over the A5H2. That is probably the simplest model, not the best, but easier for a user.
A suppressed only 12.5" 5.56 AR A5H2 can run with a very wide span of operation. This can be ideal for many, but the reduced mass may not suit users when the can is removed.
Clear as mud? It's not.
Tag for updates as I'm running a 12.5 with A5 and I'm very interested to hear what others have to say about buffer weight. I was planning to tune it unsuppressed with an A5H2 and see how it runs suppressed after that.
That can be a very viable option without a can. With a can that can be a good option to increase mass as long as you do not run out on available mass options.
BoringGuy45
08-29-16, 20:20
No reason not to go a5 on a new build. Be warned, all your other lowers will grow a5 extensions too!!
Get the bcm 8pos or new magpul 10pos tubes. I suggest going with an a5h2 buffer and tuning your agb to the a5h2+can. That way you have the option of dropping to a5h0 buffer w the can off as Tom is suggesting.
You could tune to a lighter buffer, but I like to have a little extra weight in the action to keep reliability up when dirty or dry to really whack rounds out of the mag.
I'm putting my Magpul SL on this build, so I think the BCM 8 position might be too long (wouldn't be able to collapse it all the way). Also, I was unclear on the new Magpul buffer tubes; are both the 7 and 10 position ones A5?
I think that only the 10 position tube is A5 compatible.
crosseyedshooter
08-29-16, 20:35
I'm putting my Magpul SL on this build, so I think the BCM 8 position might be too long (wouldn't be able to collapse it all the way). Also, I was unclear on the new Magpul buffer tubes; are both the 7 and 10 position ones A5?
I believe all the A5 extensions are the same overall length, but the extra hole position may be to accommodate standard carbine stocks like BCM/CTR/M4, etc. The BCM 8-position allows BCM carbine stock to fully collapse with maybe 1/2" gap to the castle nut, I'm assuming this locks in the second hole position of the 8 holes. A Magpul SL stock and Vitor 7-position will collapse to the first hole position and there is no gap to the castle nut.
Without triggering the need for safe spaces, most of this has been covered. I have made several posts about the A5 to include the barrel length and even the port sizing.
When I want the SBR to shoot smooth, I also top it off with an LMT enhanced carrier.
BoringGuy45
08-29-16, 21:54
I believe all the A5 extensions are the same overall length, but the extra hole position may be to accommodate standard carbine stocks like BCM/CTR/M4, etc. The BCM 8-position allows BCM carbine stock to fully collapse with maybe 1/2" gap to the castle nut, I'm assuming this locks in the second hole position of the 8 holes. A Magpul SL stock and Vitor 7-position will collapse to the first hole position and there is no gap to the castle nut.
This video is what I was wondering about:
https://www.youtube.com/watch?v=UnrVJT4UU10
I believe all the A5 extensions are the same overall length, but the extra hole position may be to accommodate standard carbine stocks like BCM/CTR/M4, etc. The BCM 8-position allows BCM carbine stock to fully collapse with maybe 1/2" gap to the castle nut, I'm assuming this locks in the second hole position of the 8 holes. A Magpul SL stock and Vitor 7-position will collapse to the first hole position and there is no gap to the castle nut.
That is exactly right. The MAGPUL 7 position is an improved carbine tube and the 10 position is A5.
A magpul SL stock will close all the way on any A5 stock, including bcm.
This video is what I was wondering about:
https://www.youtube.com/watch?v=UnrVJT4UU10
This video shows the 2 vltor branded a5 tubes and a carbine tube. The 6 position a5 was for regular stocks. 7 position a5 for extra long stocks designed to close to the castle nut on the longer a5 tube. Besides the number of positions they are the same product.
No reason to do all that now if you have even more positions to ensure ALL stocks will collapse as far as possible onto the tube while still engaging a position hole.
BoringGuy45
08-30-16, 16:44
Well, I ordered the 8 position BCM A5 tube!
BoringGuy45
09-07-16, 22:48
Okay, so my Magpul SL stock fits perfectly on my BCM A5 tube. I only got the tube; no spring or buffer yet. Now, for some advice: what would be the best buffer to start with? Should I go with their default A5H2 to start, or heavier or lighter? Unfortunately, I won't be able to shoot my rifle until, God willing, November or December when the stamp comes back.
All I can say is that my 12.5 BCM with LMT enhanced carrier and A5H4 runs fine suppressed and unsuppressed with 5.56 ammo.
Okay, so my Magpul SL stock fits perfectly on my BCM A5 tube. I only got the tube; no spring or buffer yet. Now, for some advice: what would be the best buffer to start with? Should I go with their default A5H2 to start, or heavier or lighter? Unfortunately, I won't be able to shoot my rifle until, God willing, November or December when the stamp comes back.
BoringGuy45
09-07-16, 23:40
All I can say is that my 12.5 BCM with LMT enhanced carrier and A5H4 runs fine suppressed and unsuppressed with 5.56 ammo.
Duly noted. If I was going to do something other than the "default" weight, I was thinking about going to the heavier route as I plan on suppressing it often.
It will also run with an A5H3. I opted for the heaviest and 9K rounds later it seems to be fine. If I was a little concerned about excess carbon, dirt, etc.. I would maybe go back.
Duly noted. If I was going to do something other than the "default" weight, I was thinking about going to the heavier route as I plan on suppressing it often.
MajorLonghorn
09-08-16, 23:00
I had SOLGW build me a 16" midlength rig with an A5 buffer system, a SLR adjustable gas block, and a Sionics NP3 coated BCG. It runs clean and shoots soft. I love it, especially with the Sniper Grey Cerakote.
BufordTJustice
09-09-16, 08:58
I believe it is IG who has some good info on here about SBR's with A5's and running them supressed/unsuppressed. I would look into those posts. A lot to be learned in there.
Running my Sionics Reduced Gas Port 11.5" with an LMT e-carrier, A5H4 buffer, tubbs AR10 flat wire SS spring, and SLR Sentry 7 Ti gas block. Runs super soft with and without can.
Added benefit: zero gas to face.
For those of you using an adjustable gas block with the A5 system for suppressed and unsuppressed use, is there any benefit to tuning it to run with an A5H4 as opposed to an A5H2?
BufordTJustice
09-09-16, 09:29
For those of you using an adjustable gas block with the A5 system for suppressed and unsuppressed use, is there any benefit to tuning it to run with an A5H4 as opposed to an A5H2?
Seems to be. There is apparently a synergistic relationship between the AGB, LMT e-carrier, and A5H4 buffer in terms of function and gas blow back over using an A5H2.
In fact, ready to have your mind BLOWN? I can, and have, run an A5H2 at the exact same gas settings. Which seems to defy simple physics, but i suspect the heavier buffer puts the overall timing of the gas cycle on the friendlier side of the chamber pressure curve during extraction, because going from 5.2oz to 6.8 should have an observable effect on function after having my AGB adjusted one notch away from not locking back.
Yet, here we are. Also, the A5H4 is REALLY smooth.
In fact, ready to have your mind BLOWN? I can, and have, run an A5H2 at the exact same gas settings.
That's good information to know. Thanks. Out of curiosity did you ever try tuning the gas down for the A5H2?
BufordTJustice
09-09-16, 11:34
That's good information to know. Thanks. Out of curiosity did you ever try tuning the gas down for the A5H2?
I did. I couldn't turn it down any lower than with the A5H4.
Dang, I get the mind blown part now. I really appreciate the input. It'll come in useful as I finish my setup.
Buford (or others), what size was the port on the sionics reduced port barrel? I ask because I have been playing with the same parts on a chopped 10.8" barrel with .069 gas port. With the sionics np3 carrier and green spring it would cycle and A5H4 but when dirty would not lock back, same with A5H3, even had some with the A5H1 after shooting suppressed and dry and dirty.
Putting in a mil spec rifle spring seemed to solve the issue, which was surprising because the springco spring isn't supposed to be any different in eight, just longer life.
Then I took the the LMT enhanced carrier with bcm bolt out of my other SBR, thinking it could be ideal with the small port, but it had failure to lock back when empty, and no problem when I put the sionics np3 bcg back in, it had gotten a quick wipe when I took it out, so was relatively clean. I was surprised because I thought the LMT carrier would lock back easier.
*this was with pmc bronze I purposely used to test the range of function
** This is meant to be a dedicated suppressed SBR, but when built it was tested with a standard carbine (weight) buffer, not with the A5. But Id still like to set it up so it will work non suppressed and run it 50/50 for a while
With a fixed amount of energy applied to the action system to perform work, there are ways to use that in different ways to perform the functions for proper cycling of the action. So let's compare a lower reciprocating mass to a higher reciprocating mass that both function well within a cyclic rate range, It's important to know that this is not across the board for all, this tends to fall into place for some, not all. In a overly basic form for this topic to keep it simple, let's take a look at their attributes.
A lower reciprocating mass requires less of that available energy to move. That initial action movement happens earlier, the cam action happens earlier to unlock. The amount of tensions required to unlock may be higher at that time than if it was delayed slightly to allow residual pressures/ tensions to drop. That earlier initiation of unlocking can burn up the rest of the energy applied during a complete cycle of the action.
A higher reciprocating mass requires more of that available energy to move. The initial action movement happens later, the cam action happens later to unlock. The amount of tensions required to unlock may be lower at that time than if it was initiated slightly earlier before with higher pressures/ tensions. The later initiation of unlocking can burn up less of the provided energy, but with more energy being used to move the action initially, it can properly complete the cycle of that action.
This is in no means to say that this happens the same way for everything all the time, it is not. There are some possible combinations that tend to do better with this.
This is over simplistic by intention. There's many more details that could be looked at. Even with more details, It's still just a balance of vectors of forces in time.
tom, able to give your thoughts on my two different bcg scenario above (in non-engineer terms)?
Buford (or others), what size was the port on the sionics reduced port barrel? I ask because I have been playing with the same parts on a chopped 10.8" barrel with .069 gas port. With the sionics np3 carrier and green spring it would cycle and A5H4 but when dirty would not lock back, same with A5H3, even had some with the A5H1 after shooting suppressed and dry and dirty.
Putting in a mil spec rifle spring seemed to solve the issue, which was surprising because the springco spring isn't supposed to be any different in eight, just longer life.
Then I took the the LMT enhanced carrier with bcm bolt out of my other SBR, thinking it could be ideal with the small port, but it had failure to lock back when empty, and no problem when I put the sionics np3 bcg back in, it had gotten a quick wipe when I took it out, so was relatively clean. I was surprised because I thought the LMT carrier would lock back easier.
*this was with pmc bronze I purposely used to test the range of function
** This is meant to be a dedicated suppressed SBR, but when built it was tested with a standard carbine (weight) buffer, not with the A5. But Id still like to set it up so it will work non suppressed and run it 50/50 for a while
A 10.8" is really pushing it, a 11.5" carbine gas 5.56 AR is as short as I care to try anymore, improved function can be had with that differently. There's a lot of variables there and my intention was to keep the open discussion simple without going too deep into things.
Per an email bomb, please don't email me needlessly. Yes, the same force applied to move the BCG to cycle the action places force onto the bolt, relieving some tensions to the bolt and BE. A higher reciprocating mass does apply more force to relieve bolt lug unlocking stresses than a lighter one does due to mass. The bolt is an internal piston in this system.
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