Stove Piping

I am having a stove pipe issue with my AR15 SBR.

Here is a few bits of info:
  • It's new. less than 300 rounds.
  • It's clean. Detailed strip and clean.
  • It's an SBR. 7 inch. LOUD.
  • It was well lubed. Even over-lubed eventually
  • Ammo was new and consistent.
The next thing I am going to try is swapping out the lower with the pistol lower I originally had on this rig. It ran fine in the past with that lower.

My theory is that the buffer spring is too strong because the barrel is so short and the recoil is so light.

Any other ideas?

--Yes I assembled the thing myself? What are you saying!?


That Guy said...

Check your gas key. Mine was doing mysterious jams, including stovepipes, and one of the gas key screws had sheared off. everything LOOKED fine, but the key was loose making it seem like it was under gassed.

Laura said...

i was told by an AR gunsmith that over-lubing can cause problems. mebbe that's part of it?

New Jovian Thunderbolt said...

cheapest and easiest check... swap that buffer tube spring for a shorter one.

then fiddle with the gas key.

i doubt it is over-lubing, Laura, you should see how dry he leaves it, normally.

Laura said...

eh, was just a thought. :)

Anonymous said...

I would have thought the buffer spring was too weak and allowing the bolt to slam back too fast and pop the extractor off the rim.

Or the extractor spring is screwed up in some fashion.

JB Miller said...

I have run it dry, a few drops in the lube holes and wet with lube. All the same.

I swapped back the original pistol lower.

Went back to my range again every third shot was a stovepipe just like the pic.

The action goes back far enough to pick up the next round so it is getting enough gas to go back far enough.

I will keep looking.

Old NFO said...

You probably tried different ammo also, right?

Anonymous said...

make sure the gas tube is clear, end-to-end.

A buddy had a blown primer get stuck in his, and caused all kinds of problems.

JB Miller said...

I did try different ammo. I also did a detailed inspection of the ammo and casings.

It seems to be getting enough gas through the tube. Enough in fact to cycle the bolt back far enough to load the next round. You can see in the photo the next round is half way in the pipe.

It's either not letting go of the spent casing or it's somehow bouncing back in.

B said...

Shorter buffer. THe bolt may move far enough to pick up another round, but not hard enough to kick the case out of the extractor properly.

David said...

I'd tend to vote with those calling for a lighter buffer assembly; standard buffer might be slowing the BCG too much to kick the extracted case clear.

Could simply be a jacked-up extractor not releasing the spent you have a different BCG you could throw in there?

Or it could be under-gassed for some reason.

Or I might not know what the hell I'm talking about.