Which Carbine Buffer for 18" Rifle-Length Gas System?

AR/M4 AR Technical Discussion
1

I’m working on an SPR-ish build and using an 18" Rainier SPR profile barrel with a rifle-length gas system. I’ll be using a carbine buffer tube. What buffer should I be using?

2

I’ve ran an H2 just because I have one, works fine for me.

3

H3 is the same weight as a standard Rifle buffer. That’s what I run in my 18in BCM SS410 3gun rifle

4

Pretty much what John said. I would be running the A5 or an H3 with a blue Springco spring.

5

Just curious as to which A5 buffer you think is best on this setup? I have the standard A5 on my SBR setup and it runs well but I like the 18inch rifle setup as well if I ever buy another rifle it will have the A5 again.

6

I have an FN military 20" rifle barrel and I use the Vltor A5H3 buffer with a green Springco spring.

7

Since we’re on the subject, I may as well run this past you. I recently completed a Noveske/BCM build using a BCM 20" SS410 barrel with a stock A5 buffer (A5H2) and it won’t cycle (short strokes) Mark’s 77 SMK loads. It runs 193’s fine. I really only did a function check & rough sight in with it. For shits & giggles I swapped lowers with an H2 buffer & it cycles the 77’s fine. It literally has less than 3 mags through it at this point. I wasn’t gonna worry about it till after I ran a few mags of 193s through it. Does it sound to you that this is just a “break in” issue or do you think it should cycle the 77s right from the get go?

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8

I don’t know what gas port size Rainier uses, but if it’s regular A2 20" size, you might get some short strokes in the cold weather with a H3.
I agree with the guys recommending the A5. That should give the best reliability. Smoother shooting with the A5 doesn’t hurt anything either.

9

I don’t know anything about the handloads per se. But, I have fired it with M193 (Federal and IMI), M855, Hornady Steel TAP (55gr. and 75gr.), markm 60gr. loads (I call them .223+) and I have never had any issues. Of course, I use Springco springs exclusively so maybe that is a factor.

The Vltor A5H2 weighs around 5.33 and the carbine H2 weighs around 4.6. So I am not sure why it is happening since I know that a 20" will run with a carbine H3 buffer. In fact a rifle buffer weighs around 5.1-5.3 oz. so my guess is that it’s an ammo issue.

10

Could very well be. I’ll give it some time to loosen up & see what happens. I may have to make some adjustments to the load. Thanks.

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