Home Forums Hunting & Shooting AR and Tactical Rifles Carbine vs mid length gas block

Maybe you are right TWR, but like I said, with full house GI ammo it'll run great with any lower configuration. It's only when you drop a grain or so it'll give issue. These are loads that run great in other guns so that isn't an issue.

My whole point is once you change the "recipe", you may have to change something else as well to get it to balance.

Changing the "recipe" has screwed up lots of guns but you have to remember tomato soup has to start with a tomato. The standard is only one weight rifle buffer and spring. If one won't run on the standard buffer/spring, it's time to look for the problem.

JP and some of the others used lighter and heavier buffers, carriers, springs and such to reduce recoil and muzzle jump to increase speed of the follow up shots. A very specialized and finicky proposition.

I do know of one 70's made Colt SP1 carbine that will not run with an A2 stocked lower. Evidently the gas port was sized to run with the lightest carbine buffer but that's strictly on a 16" barrel and carbine gas system.

What's the load it won't run?

The JP stuff isn't finicky, it runs great as designed, their just isn't any "reserve" for a really dirty gun, it'll get sluggish faster than stock. Match guys know how long they can go without cleaning, and if it wasn't reliable, they wouldn't be entering sponsored money matches with something that they thought would choke.

LC brass, WW primer, 55gr Montana Gold FMJ, 25.5 gr TAC.

Have you tried running a different BCG with that upper to see if that could be the issue? I suspect you have, but thought I'd ask anyway.

That load, with the exception of WSR primers, is pretty standard and should run.

"their just isn't any "reserve" for a really dirty gun, it'll get sluggish faster than stock"

That's what I call finicky. There's lots of ways to increase this or decrease that but the one fact I always go back to is how was it designed to work. I don't want to beat my guns to death yet I want them to run and run and run... I've run a low mass carrier, light buffers, heavy carriers, extra power springs, etc., etc. Maybe I just haven't come up with the right combonation that will beat the way it was designed.

Was just reading this and was wondering if this could be part of the problem I saw this weekend. Was with a guy shooting a Bushmaster Predator using some reloads that I had loaded for him. The rifle would not reset the trigger it appeared that the bolt was not cycling far enough to get the hammer to catch on the disconnect. The bolt would pick up another round but the trigger would not be reset. Could cycle the bolt by hand and the trigger would reset. Even had it to double fire a few times...the load that I had loaded was 22gr/H335 68Gr/HPBT CCI400. Could it be that the bolt was not cycling far enough back to make the trigger operate properly?

Yes that was the problem. You were at the starting load for the bullet and powder you were using. You could go to a lighter buffer and makes sure you have the bolt properly lubed or increase the powder charge another grain or grain and a halve.

Possible but sounds like a trigger problem since it doubled, probably a bad disconnector.

Load one round in a magazine and fire it, it should lock the bolt back, repeat 10 times. This will tell if it's a gas/ammo problem or not.

I've not used H335 yet so I don't know about the load but it sounds reasonable since I'm looking at a 28 gr load with 50gr bullets to try myself.

It's funny, playing with different buffers, I've had the bolt beat the magazine follower and skip a round, then I've had too heavy a buffer and wouldn't lock back and was sluggish. Always seems to be the same combo it was designed around that works...

H335 did the same thing in my AR 20 Practical with the rifle length gas tube . I changed to H4895 and it worked fine. One other thing with the Tubb's Spring it wouldn't work either load reliably, went back to the spring that came with the buffer kit and it worked great.

So with the wylde chamber or 5.56nato a person would need to move more to the upper end of the reloaing dat.

Gas systems work their best at certain pressure levels or pressure curves . I would at least go to the medium book level on my loads in the semi-autos or try another powder.

I'd guess trigger issue as well. I actually had this same problem this weekend with an AR I recently built. Well, I actually had a few issues because I was trying some different things. First the AR would not cycle on it's own, too heavy of a buffer spring, but I suspected that this might be an issue before I even shot it. Changed out the buffer spring with a friends 6.8 and it fixed the problem, and his 6.8 works great now too (no twang and almost no recoil now). Then once I got my rifle to cycle, the trigger would not reset. For some stupid reason I never preformed a functions check on it prior to shooting, or if I did (which I cant recall doing) it worked then. Anyway the trigger would reset if I pushed it forward after cycling, so that lead me to believe there was something wrong with the disconnect. On a visual inspection with the upper off you could see it get hung up. I lightly brushed the surface with a fine flat needle file, then some 1000 grit paper, then some polishing compound; no more hang up, and the trigger (RRA 2 stage) is slightly lighter on the first stage now too. Functions check is a go now, so now I just have to get back to a range and put it through it's paces.

H335 is just barely faster than TAC, it should run fine in an AR, as I've used faster and slower... but I tend to load all I can get, no need for light loads.

So I am dumb regards this, I have H2 buffers in one carbine gas and one mid gas, both mil spec buffer tubes, both collapsable stocks, both purchased complete from factory, both work with everything and all the time. I bought an LMT defender 2000 lower with an H3 buffer thinking to use it if I built a 300blackout, I sold it recently because I lost interest in that idea. So it probably will not work with 5.56??? I better call the guy and tell him.

I run H buffers in my middies and have run H2 buffers in my carbines without issue. Set your gun up for 5.56 pressured ammo and the H3 will probably work fine. Throw in some Rem UMC 55gr FMJ and it will probably choke.

It all depends on what ammo the gun is setup for. My first Noveske 18" SPR barrel is an intermediate gas. I figured a standard carbine buffer would be the one to use. I ran some XM193 ammo through it only to have it cycle so fast it would skip stripping a shell out of the magazine toward the bottom of the mag. I called Noveske and was told their barrels are setup to run MK262 ammo in 120 degree heat, ie., lots of pressure. A stuck an H buffer in their as they requested and it ran fine.

Each gun is it's own, a 223WSSM I worked with, needed a 9mm buffer and an extra power spring or it would pull the rims. The guy stuck a Tubbs weight system in his carrier and a Tubbs spring(because someone told him it was what he needed) and had to drop back to a carbine buffer. It was all my fault of course...

So if you was to swap out an A2 stock on a rifle length say 20" barrel gun then you would need to run what type spring and buffer. Man I thought this AR stuff was suppose to be easy..Jezz..

Hard to say, my cousin swapped 2 or 3 of his 24" barreled uppers to carbine stocks and besides his 223WSSM, he had no issues with standard carbine buffers. But never tried one on a 20" barrel.

VLTOR/BCM developed the A5 stock for the Marine Corp. It has been said that a carbine stock on a rifle barrel doesn't work 100% of the time (although Canada's C7/C8 has been doing this for years) and this new stock cures the problems.

I had a 20 inch Fulton armory upper on a RRA lower that shot xm193 fine, I think the original upper was a mid length gas as from the factory. Glad I read all of this for future reference. I may need to tell the fellow I sold the LMT too about the H3.