I have recently switched gears and have been building some 20" rifle length guns because I really like how smooth they are in comparison to the carbine length system. The question is, is there a way to get these things to run reliably with lower pressure non-nato ammo. They work flawlessly with anything that is up to nato specs but I have only been able to get about 3 rounds out before a malfunction with anything that isn’t. Is there a secret buffer/spring combination out there?
my BCM 20" upper works with wolf ammo, didnt do anything special its just the typical rifle buffer and spring
a 16" midlength will shoot just as smooth as a rifle upper probably. On my 16" middys I use H buffers and it shoots wolf and steel case fine.
Rifle length buffer/spring, stock assembly? or carbine?
my 20" has an A2 stock with rifle buffer and spring
my 16" middy has H buffer, carbine buffer tube, and spring
My old 20" Colt HBar ran fine with 223 or 5.56. My current 20" with Lothar-Walther barrel and carbine extension with carbine buffer also runs fine on 223 ammo.
223 ammo isn’t “lower pressure”. It’s loaded to safe pressures in 223 SAAMI spec chambers. 5.56 chambers will give lower pressures with the same loads compared to a 223 SAAMI chamber
Mine eats any .223 or 5.56 I feed it. No special combo of buffer or spring needed. For reference, my rifle uses a Green Mountain barrel.
I’m assuming your rifle is short-stroking. How wide is your gas port? Is the FSB or gas block aligned with the gas port?
I am getting short stroking actually.
I’ve tried 2 colt uppers so far, one an A1 the other an A2, both 1960’s era I was told. I mated them both with cavarms lowers, which I was told was carbine length RE, and tried from a carbine buffer up to an H3 buffer with no success. I didn’t try rifle length because I didn’t think you could with the cavarms lower. One LPK is a G&R the other a DD, with BCM re spring, buffers and BCG. Brownell’s mags with either green or magpul followers.
Shoots great with m193 & ss109 regardless of buffer. PRVI, UMC and wolf are a no-go. Short strokes about every 3-4 rounds.
I have no Idea how wide the gas ports are, I assumed they were milsurp and in spec. since they were small hole, but anything is possible.
The FSB’s appear straight to me, they definitely shoot straight enough. I’ll pull one off to see if there’s any indication of them being canted.
I have a green mountain barrel that I am in the process of putting an ACE ARFX stock on and before I do everything I wanted to see if I could get the cheaper stuff to work.
My brother’s 20" Palmetto State upper runs just fine on Remington UMC .223. It’s on a lower with a carbine length buffer tube and a carbine buffer.
Carbine RE… Do they function on a rifle RE?
The gas port on the FSB could be slightly forward of the gas port on the barrel, just enough so that there’s enough of a blockage so that the bolt carrier isn’t getting enough gas when shooting with .223. That’s what I was getting at.
A rifle system should work all day long with good .223 ammo. PMC Bronze and shit steel cased might choke it. But any decent .223 should run flawlessly.
Don’t get into this aftermarket spring nonsense. If a gun needs some idiotic colored spring to run right… replace the gun. :rolleyes:
I’m not using special springs, standard carbine or rifle. Guess I need to take’em down and do some inspecting. Thanks to all who responded.
What ammo are you running?.. Like I said… some ammo, Like PMC bronze has the wrong propellant in it.
Stuff like that has choked my 20 inch guns. No one notices those problems because most people are shooting carbine or middy gas systems.
PMC bronze is one, PRVI mostly, some golden bear, winchester white box and I think I had some wolf classic rolling around the range bag. None of which offered anything different. About 3-4 rds. then a malfunction.
My bone stock Colt Hbar A2 20inch barrel works just fine on Wolf, Silver bear PMC. Clean them Lube them and try different mags.
I did have a short stroke problem when I was shooting Tula crap out of old steel mag but when I loaded up a Pmag and re lubed her up she was up and running spitting some lube out but still running. Not the cleanest day of shooting Lube Plus Tula = muck and gunk…
I burned through all of the PMC ammo I bought on sale during the Magpul course. Zero issues with it.
Yep. Works great in short gas systems. Robb Jenson is the one that pointed out it chokes in Rifles.
I went and tried mine, and sure enough… This was a few years back. It’s possible they’ve changed the propellant since.
OP
Not the same barrel length, however my MK12 runs all the .223 ammo I’ve put through it. The barrel is an 18" Douglas SPR barrel.
I bought about 800 rounds of PMC bronze sometime last winter. I shot about 600 of it through two different rifle length gas systems. No issues at all. So, maybe they have indeed changed their recipe.
I would hope so. It’s really so easy to make ammo that runs a broad spectrum of gas systems.
These foreign banana’s are constantly getting it wrong.
I just found two magazines with some of it loaded. We’ll have to try it out and see.