Buffer weight for SBRs?

Keith03

Newbie
I will have to shoot it again this weekend and look at the ejection pattern closer. I will give up mild 223 to gain durability with 556 loads.
I shot a verity of ammo with and without the can.
Even AE 223 and 55g 223 pressure handloads never got the the right of 2:00. Even without the can.
As one would expect the higher pressure ammo, can, etc pushed things to 1:00.
Mk262 was 1:00 with and without a can.
 

Yondering

Regular Member
Keith, that's seriously overgassed even without the suppressor. I'd be concerned about long term durability with that setup, as it's beating itself pretty hard.

Personally, I wouldn't even bother trying to fix that with heavy buffers, I'd go straight to some sort of gas restriction, like an adjustable gas block, or bushing in your current gas block. Does that rifle have a low profile gas block under a handguard, or something like an A2 front sight block?
 

Keith03

Newbie
It has low pro gas block under the handguard. I think those were some sort of special material gas block to survive 10" 5.56 suppressed abuse right?
I ordered that upper December of 2015 if anyone has a timeline on DD MK18 gas port sizes. This is why I have never shot it much.
 

Yondering

Regular Member
I'm not sure on the "special material"; as a machinist that doesn't sound right to me, but ?

Regardless, there are a number of good options for replacing that with a low profile adjustable gas block, which is your best option for fixing the gas issue, and one of the few options that's not a band-aid. My preference is something like the Seekins adjustable blocks; set it once, lock it down, and forget about it. I'm not really a fan of the "click adjustable" blocks, and don't have anything good to say about the Superlative "bleed off" system.
 

OK-5-0

Member
Would guess SLR, they OEM the DD low profile gas block already.


Sent from my iPhone using Tapatalk Pro
Update, the adjustable gas block was a temp fix from DD. They are now making new barrels for us with the correct size gas port for suppressing. At no cost to us I may add. I’ll be happy when this is all over but DD came through with some outstanding customer service.
 

5150Magnet

Amateur
I'm guessing it also varies based on the ammo being used, but from what I'm see from most the lightest weight buffer is a H. I have two 11.5 AR pistols which both use H buffers and so far I have shot a bunch of 55gr and 62gr with no issues. Understanding not to go below 10.3-10.5 length otherwise you might run into reliability issues I'm also seeing a lot of you guys lean towards using H2 and up. No experience with suppressors due to where I live so that side of things is completely foreign to me.
 

Dpvaz56

Member
Out of interest but does anyone use an H3 for an unsuppressed 10.5 or 11.5? Also, anyone have any experience using the Geissele Super 42 with a 10.5” or 11.5”?
 

marcusa

Member
Sharing a recent experience/email with Geissele CS.

Recently acquired a URGI 10.3 which came with the Super 42 and H3 buffer. Pretty much immediately replaced one of the tungsten weights with steel to make the buffer an "H2". Installed with a LAW adapter, I was finding operation to be sluggish with .223 ammo and that the bolt wouldn't lock back even with some 5.56 options, primarily 55gr. I did experience a couple short stroking malfunctions especially in cold weather.

I've been exchanging a few emails with Geissele CS, but the TL;DR is that the LAW adapter adds 2 oz to the BCG and changes the recoil dynamics. Currently running with the Super42 and a "Carbine" buffer (removed all three tungsten weights and replaced with steel), and now cycles all ammo I've tried so far. Curious if others have had similar experience.

From Geissele CS:
Thank you for the update. The law tactical folder does have a space that adds a few ounces so It would not be a true H1/H2/H3 and additional tuning would be required. Would you be able to tell me if it is now running in the H1 configuration?

My latest response:
Thanks for following back up. I did exchange one of the tungsten weights with steel to make the buffer a "H1" with the super 42 spring. I found that function was improved, but that the bolt would still not lock back consistently on the last round, depending on ammo. Federal M855 worked without issue, but cycling was sluggish and locking back was inconsistent with 55gr Wolf Gold .223, 55g Federal AE .223, IMI M193, CBC M193, Speer Gold Dot 62gr and Gold Dot 75gr. What surprised me most was that Federal Mk318 62gr OTM would not consistently lock back. I am running unsuppressed and brass ejection is somewhere between 4:30 and 5:00.

According to LAW Tactical's website, the buffer extension weighs 2 oz. Exercising some google-fu:
Carbine buffer weighs approx. 3.0 oz
H1 buffer weighs approx. 3.8 oz
H2 buffer weighs approx. 4.6 oz
H3 buffer weighs approx. 5.4 oz
H4 buffer weighs approx. 6.8 oz

So with the LAW adapter the overall weight of the cycling system (less BCG) is:

Car + LAW = 5 oz (between H2/H3)
H1 + LAW = 5.8 oz (>H3)
H2 + LAW = 6.6 oz (~H4)
H3 + LAW = 7.4 oz (>H4)

Since the Super 42 is an extra power spring, I'm guessing that an H1 buffer plus extension at 5.8oz, heavier than an H3 - is causing the issue. Next step is to try to replace the last tungsten weight in the buffer with steel to make it equivalent to a standard carbine buffer, which would put the total weight of the buffer and LAW extension between a typical H2 and H3 weight, which would be within the recommendations for a 10.3" with carbine-length gas system. Unfortunately I don't have a suppressor to test, but I wonder if the 5oz combined weight would be a pretty sweet spot between suppressed/unsuppressed.

If you like I'd be happy to report back after the buffer swap and range trip.
 

JPate

Newbie
I've had an H2 in my 11.5 BCM but just switched over to the H3 as I felt the recoil was more harsh than it should have been. I run unsuppressed exclusively with 5.56 and the Geissele Super 42 buffer
 

J-rad

Newbie
H2 for a Triarc 12.5” mid length, Armaspec SRS H2 on a 20” Rainier ultra match. The 12.5 Triarc seems to like the H2, the Armaspec H2 and 20” rifle length is $$$ though longevity is yet to be proven.
 

shoobe01

Established
FWIW, my SBR is a no-name lower we won't discuss, but has mostly been replaced with good bits over time. Has an H buffer and gets uninteresting chrome-silicon springs.

I have three uppers:
  • 12.5" BCM 5.56
  • 10" .300 through DSG but made by Seekins
  • 10" 9mm, originally some no-name junky thing, but some bits replaced and for example now has an authentic Colt SMG receiver
And, a suppressor. Both the 5.56 and the .300 both use that a lot.

Works.

100% of the time. Never change the buffer, never had to put an adjustable gas block on. I did do that to the .300 to make it even less gassy, but it wasn't needed for reliability.

I feel left out. Or like I am doing something wrong that it just keeps working when I clip on my upper or screw on the suppressor. H. Not H2, or 3. Just H.

???
 

J-rad

Newbie
For
FWIW, my SBR is a no-name lower we won't discuss, but has mostly been replaced with good bits over time. Has an H buffer and gets uninteresting chrome-silicon springs.

I have three uppers:
  • 12.5" BCM 5.56
  • 10" .300 through DSG but made by Seekins
  • 10" 9mm, originally some no-name junky thing, but some bits replaced and for example now has an authentic Colt SMG receiver
And, a suppressor. Both the 5.56 and the .300 both use that a lot.

Works.

100% of the time. Never change the buffer, never had to put an adjustable gas block on. I did do that to the .300 to make it even less gassy, but it wasn't needed for reliability.

I feel left out. Or like I am doing something wrong that it just keeps working when I clip on my upper or screw on the suppressor. H. Not H2, or 3. Just H.

???
For what it’s worth I ran a 12.5” carbine gas with a carbine buffer suppressed, this resulted in a very deep scoring in my upper receiver from my cam pin and a bent gas tube that locked up the action.
 

Farmboy20

Regular Member
Question for this thread with the a5 system what all does that entail. Rn i just have a pistol lower with a sb a3 brace on it, with a standard carbine spring and buffer in it while i wait on my 12.5 5.56 triarc upper to come. Is the A5 system just a spring and buffer i can buy and throw in my lower or is there more to the system?
 

marcusa

Member
Question for this thread with the a5 system what all does that entail. Rn i just have a pistol lower with a sb a3 brace on it, with a standard carbine spring and buffer in it while i wait on my 12.5 5.56 triarc upper to come. Is the A5 system just a spring and buffer i can buy and throw in my lower or is there more to the system?

The A5 system is an A5 buffer tube, spring and A5-specific buffer. The tube itself is slightly longer than a standard carbine tube, the spring is a rifle-length spring (Vltor or Sprinco green) and the buffers themselves are also slightly longer than a standard carbine buffer. Although they are labeled similarly, i.e. A5H1, A5H2 the weights are also not the same.

For the system to work properly you will need an A5 length tube (Vltor, BCM makes one as well), rifle-length spring (Vltor or Sprinco green) and the appropriate A5 buffer for your setup.
 
I've experimented quite a bit with my DD MK18 upper (produced in 2018 with a 0.070" gas port). When I built my lower I originally went with a Sprinco Blue + H2 buffer and had lockback issues in cold weather (the gun operated fine in warmer months and/or indoor ranges). I switched to a standard power spring with better results, but it still felt sluggish. Later down the line I added a Law Gen 3-M folder and had lockback issues even in warm weather. I ended up having to switch to a 3 oz carbine buffer for reliability. Brass ejection was weak in the 2:00 to 3:00 direction. I've kept the Law adapter, but I eventually switched the buffer system to an A5. I'm currently using an A5H0 (3.8 oz) and standard rifle spring. The gun has been reliable with this combo, but ejection is still weak in the 2:00 direction. I'm waiting for a SOLGW BCG to be in stock so I can try that and see if ejection improves.

------------------------------------------------------------------------
I also built a similar lower for my dad's BCM 12.5" Kino upper. That gun runs like a sewing machine using the Law adapter, A5 buffer, Sprinco Green spring, and A5H3 buffer. Despite the combined 8.3 oz of the buffer + adapter plug and the extra power action spring, ejection is strong, and brass ejects consistently in the 4:00 direction. You could catch his brass in a coffee can!
 
Top