Stovepipes - 16" Grendel and AR10

[zekers7]

Im having the same issue with my AR10 and Grendel. Both are stovepiping once every 6-10 rounds. After a string of shooting with the AR10 it was the same result every other shot.

Grendel:
16" JT barrel with carbine length gas
Carbine spring
H3 Buffer

AR10
Mega arms 16" Barrel with mid-length gas
DPMS BCG, DPMS 308 carbine spring and 308 carbine buffer

I ordered + strength ejector/extractor springs as well as a wolff XP carbine spring for the grendel. My only thoughts is that both systems are extremely over-gassed.


problem has been solved. An adjustable gas block worked wonders on both rifles. I switched both back to the lightest possible spring/buffer setup possible and tuned the gas down to what would reliably cycle the action unsupressed. Not only did this solve the stovepipe/extract issue but it actually greatly reduced the felt recoil of both rifles. They are both MUCH softer shooting than before and honestly have no idea why ive never tried an adjustable block on my other rifles.... Day and night difference

[VASCAR2]

Is this factory ammo, if so what kind. I had similar result using an H-2 buffer with a reload with 30.0 grains CFE 223 and 123 grain Nosler CC. The CFE223 load wasn't building pressure fast enough and my rifle was short stroking. I switched to Carbine buffer and the 16" J&T carbine gas upper functioned. H-3 buffer is heavier than H-2. As the rifle gets hot on a new build might explain why it starts to malfunction after a few rounds. I use a lot of CLP on the BCG on my new builds.

My 16" J&T has a fixed A-2 front sight. Are using an adjustable gas block? Under gassed and over gassed can be hard to distinquish. If you have a carbine buffer you might try it especially if your shooting Wolf or PPU brass or steel cased ammo.

[zekers7]

it is locking open on the last round. Im going to try the plus power ejector and extractor springs as soon as they come in, watch where the brass is ejecting and try to get some iphone slow motion footage of it jamming.

[VASCAR2]

Sounds like a good plan. My extractor was biting into the cases pretty good when my J&T 16" was new. I used some fine sand paper and smoothed out the extractor which seems to have eliminated the gouged brass.

[LRRPF52]

Could be the extractor holding onto the case head.

This seems to be common enough that I see it at least 1-2x per month. If the extractor has sharp edges on the lip, they need to be toned down a bit.

[VASCAR2]

I saw on another forum the OP is apparently using a suppressor on both the 6.5 Grendel and AR-10. Might need to consider an adjustable gas block.

[Rickc]

you have the same problem on two different rifles. an AR15 Grendel and a .308 AR10.

I don't think it is the rifles. I think it is something you are doing or not doing.

[LRRPF52]

If you're shooting suppressed, that will accelerate the Bolt Carrier velocity enough to cause your stove pipes.

A good way to fight it is with a heavier buffer and longer gas system length.

CLGS 16" is one of the worst offenders for excessively high cyclic rate even unsuppressed.

[SHM1979]

I had this exact issue with my Grendel and tried all the things talked about here and more (replacing extractor/ ejector, polishing both pieces, replacing the springs for both, trying different ammo and mags, etc...) I finally took it to a gunsmith out of frustration and he put an adjustable gas block on it and solved the issue. The picture you posted is exactly what I was experiencing so I think you may have the same issue as me (I think VASCAR2 is correct and the gun may be over gassed). Here is the link to a YouTube video I put together documenting my issues and how I attempted to fix it (hopefully this will save you many cuss words and frustrating trips to the range) https://www.youtube.com/watch?v=LcCY9RkpgB0

[LRRPF52]

I had this exact issue with my Grendel and tried all the things talked about here and more (replacing extractor/ ejector, polishing both pieces, replacing the springs for both, trying different ammo and mags, etc...) I finally took it to a gunsmith out of frustration and he put an adjustable gas block on it and solved the issue. The picture you posted is exactly what I was experiencing so I think you may have the same issue as me (I think VASCAR2 is correct and the gun may be over gassed). Here is the link to a YouTube video I put together documenting my issues and how I attempted to fix it (hopefully this will save you many cuss words and frustrating trips to the range) https://www.youtube.com/watch?v=LcCY9RkpgB0

Those AR-Stoner barrels, the 18" MLGS ones, have way too large of a gas port at .0935", when they should be .076". That's most of the problem right there.

Every 18" MLGS Grendel I've built, and there have been several, have worked out of the gate. They all had .076" ports.

[zekers7]

problem has been solved. An adjustable gas block worked wonders on both rifles. I switched both back to the lightest possible spring/buffer setup possible and tuned the gas down to what would reliably cycle the action unsupressed. Not only did this solve the stovepipe/extract issue but it actually greatly reduced the felt recoil of both rifles. They are both MUCH softer shooting than before and honestly have no idea why ive never tried an adjustable block on my other rifles.... Day and night difference

[Flyguy11]

LRRPF52 Thank you for telling me about adjustable gas blocks and gas port size before I did my build. It saved me a headache.