I’m sure it’s been covered before but my Google Fu isn’t working. I’m going with an adjustable gas block as I’ll be running my FA762SS on it once I receive the brake from Surefire. My question is since I’m running an adjustable that I’ll be tuning it to anyways, is it necessary to still run an heavy buffer like an H2 or H3? The build is an 18" Rainier Ultramatch with an intermediate gas, seekins adjustable, LMT FA BCG, and a UBR stock. Eventually I plan on picking up a JP silent capture spring from a friend, but in the mean time I’d like to go with a normal spring/buffer set-up.
I use an H2 for the testing of my patent pending modular adjustable gas block. I find that an H2 is all that is needed to stop bolt bounce for full auto. Anything heavier is just adding unnecessary inertia. Even for semi auto, bolt bounce is bad and should be eliminated. This is for 5.56. For other calibers, maybe something heavier than H2 may be required. I use a standard power ‘white’ spring from Sprinco. I spoke to Alan over at Sprinco and he also recommended that I stay with the ‘white’ spring since I am controlling the gas.
Here is a link to my gas block in case you are interested: http://micromoa.com
On paper this sounds good. But in practice a heavier buffer can make the gun more stable and smooth.
If I were tuning an adjustable. It’d be to an H2 buffer for carbine, or the standard A5 buffer for the A5 system.
I’ve seen several 3 gun setups that use adjustable gas blocks and ultra light buffers like the JP Low Mass. Their point is to speed up the cyclic rate with the reduced buffer. So it kind of depends on how and what you are shooting.
Generally speaking for me anyways, when ever I am making changes to the action of the AR from the gas block to the buffer, I’ll go back to standard buffer and spring and experiment from there. Just my $0.02.
I’m sure you know, an 18" barrel with a suppressor will be long and heavy.
For a high reliability, general purpose gun, I would not plan to use any buffer lighter than H2, with the A5 preferred.
The H2 has the minimum internal reciprocal weight required to effectively eliminate bolt bounce and is not surprisingly, equal to the rifle buffer.
It is possible to play with different weight buffers when switching between suppressed and non-suppressed use, but IMO, it is FAR better to adjust the gas drive than to adjust the moving mass.
There are a couple schools of thought to approach gas adjustment for suppressor use, depending on your needs.
If you plan to run it dedicated suppressed, a fixed gas port sized for suppressor use is probably optimal.
Depending on how much back pressure the can generates, the gun may not lock back without the can.
A low back pressure can is of great value in this case.
If you plan to run 50/50 with the can, a switchable type gas block with two different tuned ports is probably optimal.
A locking “click adjustable” gas block that allows you to count clicks when switching between suppressor/non-suppressor use is probably next best.
A screw type adjustable gas block with no lock is lowest on the reliability and utility scale.
For a go-to gun with an adjustable, in theory you’re going to want the lightest buffer that can still eliminate bolt bounce, and no heavier than that. H2 seems to be a popular choice judging from this thread.
If you add any more you’re introducing unnecessary reciprocating mass, which is going to increase muzzle movement and all that.
I think the A5 system would be an exception to that… Multiple members have said that their gun seem to cycle smoother and have less perceived recoil with the heavier A5 buffers than with the lighter ones. When I get mine I can let you know for sure if I end up playing around with buffer weights.
I think the reason for less perceived recoil/muzzle movement in this situation is the spring inside the A5 buffer. Not only does it keep all of the weights forward against the front of the buffer for consistency, it “cushions” the weights when the buffer reaches the end of the receiver extension. Not to get all mathematical with the laws of physics here, but essentially what is happening is that the kinetic energy in the weights themselves is transferred over a period of time as the internal spring compresses. While more energy is transferred, the energy from the additional weight is transferred after the initial impulse of the BCG and buffer body impacting the end of the receiver extension. Regardless of the weight inside an A5 buffer, the initial impact will have the same amount of energy if the mass of the buffer body + the BCG stay constant (which they will) and the velocity of said parts stays the same as well. However, the velocity will not stay the same (unless you really crank open the gas block to pound the heavier buffer backward at the same speed as the lighter one - which isn’t necessary or desirable) because the weight of the entire system is increased (BCG + buffer body + buffer weights). This will actually reduce the initial impulse due to the lower velocity. I guess the short version of the story is that more total energy will be transferred in smaller portions over a period of time, rather than all at once, resulting in smoother operation and less rifle movement.
If analogies are your thing, think of it this way: Shoot a small car with 10,000 BBs at a rate of 5 per second. Then shoot the same car with one pumpkin fired from a pumpkin cannon. Which is going to cause the car to move more? (This is an extreme analogy, but you get the point.)
All that said, my recommendation to the OP would be to go with the A5 system and an A5H4 buffer (heaviest buffer Vltor offers at nearly 7oz.) and then tune your gas block to whatever you need to to get it to function 100%. The slower buffer speeds should give you less perceived recoil and the added reciprocating mass will actually give you a larger “window” if you will, or margin of error, when shooting different types of ammo, or shooting suppressed vs unsuppressed. Said another way, if you tune for medium 5.56 loads unsuppressed, switching to hot 5.56 suppressed, or weak .223 unsuppressed will have less of an impact on how the system functions with a heavier buffer than with a lighter one. Make sense?
It’s more of a precision rig and weight is not an issue for me. I went with an H3 and I’m gonna try out the Seekins adjustable. I’ll likely always run it suppressed for some local matches where the ranges stay under 550.
When using aftermarket non standard parts you just have to test them. Way too many variables at play.
It’s like asking what’s the speed rating of my tires if I run them with 25-30psi of air pressure instead of the recommended 35psi.
I understand. I was hoping someone else had run a similar set-up at some point and I can use it as more of a starting point.
I know this is an old thread, but its subject is spot on to a question I was going to pose. I recently finished up putting together a build that I started over five years ago. Things just got busy and it got put to the back burner. The notable things about this build are that it has a 16” mid-length gas system with a pretty thin barrel, an adjustable gas block and a carbine buffer. I adjusted the gas block to run 100% with good quality 223Rem FMJ such as Fiocchi Tactical. I primarily use 5.56x45 M193, so I figured that it will run that if it will run the less powerful 223Rem. With both types, it spits empty cases into a nice pile 5’ to 8’ away at about 4:00. The spent cases look perfect with no head smears or dings. It’s running perfectly, but I couldn’t help but think about it anyway. Would a heavier buffer be more desirable? If so, what would be the benefit? Based on what I’ve read in this thread, bolt bounce could be reduced. I’m not planning on running the upper on full auto, so that’s not a big concern. Then I got to wondering when the H buffers were invented. According to what I’ve been able to find out, it was sometime in the ‘80’s and likely corresponded with the advent of the M4. My father was in Vietnam where he was a forward observer and later commanded an artillery battery. I asked him about the rifle that he had and he said that he had what he called a CAR-15. He said that it had a shorter barrel and handguard than the M16 along with a retractable stock. I asked him if he ever had any reliability issues with it and he said no. There were no failures to fire due to bolt bounce or anything else. He said that he kept it clean & lubricated and it ran like a champ. He fired thousands of rounds through it without issue. Of course, all this happened with a regular carbine buffer. Based on his personal observations, I wonder why the H buffer is now said to be such a must have for full auto fire. I don’t dispute that it’s an incremental improvement but wonder if it’s not used more to compensate for overgassing than anything else.
The H buffer isn’t a compensation for over-gassing. It comes stock on Colt 6920s now.
I think we did an H2 swap on a Euro Colt 6920 just to see if we could tell the difference and there was no change in function or ejection that we could tell. I think I put the factory H back in just to keep the gun original.
Probably back when this thread was going, RSilvers did a breakdown of which buffer weight combined with the Colt Carbine spring most closely matched the function of the rifle buffer system. His conclusion was that the H2 was the closest match.
I run H2s in every carbine I have that isn’t a VLTOR buffer system. I only have one 14.5 middy with a .077” port where I go with an H buffer. It’s gassed so lean that the H buffer works.
If I were you, I’d put either an H or an H2 in and dial the adjustable from there. The old Carbine buffer is so light. I have no idea why that buffer was ever produced.
Why? It’s running 100% reliably, feels great and the spent cases are going into a nice pile.
It’s just what Stoner started with when the carbine was developed. Lots more data was needed for others to figure out that a heavier buffer could increase reliability.
I’ve never found any gun that ran best on the carbine buffer. If I I had a gun that wouldn’t run on the H or H2, I’d be looking for the gas leak. Some guns will tolerate the carbine buffer, but it’s less than optimal. Especially if it’s the carbine gas length.
Being that you have an adjustable block, I imagine that you’ve dialed it in for that buffer. I just prefer to mimic the Rifle system that was deemed optimal by guys with more engineering knowledge than I have.
I actually had that happen with the H buffer on the previously mentioned 14.5 middy. It started getting finnicky. The gas tube had worn badly where it goes into the key and was leaking a bunch of gas.. puking it under the handguard where I couldn’t see it.
Conversely, I would never tolerate a gun that ran better on an H3.
I run H3s on a few of my suppressed ARs (and even heavier enhanced buffers on the 10s and ridiculously heavy Slash’s buffers on the pistol calibers), H2s on the rest, they all run flawlessly. Don’t have a single one still sporting an H buffer even though they’ll run with them, they’re just smoother with the heavier buffer.
I remember my first SBR 20+ years ago. “We” didn’t know crap about port sizes and all of that back then. It was an 11.5 Sabre Defense with a massive .080+ port. Miserable to shoot, and I just assumed that was the SBR game. Sucker would outrun the magazine follower and fail to lock back the bolt carrier was going so fast.