I have an AR pistol that only sometimes ejects and other times the fired brass is rechambered  and I am stumped.


The gas port is .067 which is what it is supposed to be.

I have swapped BCGs from known working pistols.

Swapped buffer springs and buffer from known working pistols.

I have pulled the gas block and rechecked alignment I also checked to make sure there is no restrictions in the gas block or tube.

I have tried three different types of ammo as well.

I have swapped magazines, I have also swapped lowers and still have a single shot pistol.

It is wearing a KAK blade,tube, buffer and buffer spring

Last thing I know to do would be to get another gas block to see it that would fix the problem.


Any other ideas

Sounds like it's short stroking.

How are you checking gas block alignment?

Most people don't get the alignment right along the axis of the bore, assuming that the block should abut against the barrel shoulder.

More often than not, there needs to be a bit of stand-off from the shoulder to the back of the block so a hanguard cap can fit in between.

When you align the block to the shoulder, you might be choking off the port on the edge, which will restrict flow, and therefore short-stroke the action.

If the gas system is good.
Gas tube binding in carrier key?
Try a different mag?

May be short stroking and maybe not. Does the carrier go back far enough to pick up another round? If no round from the mag is being stripped off, the carrier is likely short stroking. If a round is being stripped from the mag but still no ejection then the ejector and or pin is likely not working properly.
If short stroking is indeed the reason and the same thing happens with multiple bolt carriers, buffers and springs then you have narrowed it down.
What's left to check and check again=
Barrel extension is binding on the bolt when under pressure?
Chamber is tight and stuck cases are slowing the carrier?
Gas block not aligned with barrel?
Gas tube not aligned with gas block?
Gas tube not aligned with gas key on carrier?
Bolt carrier not sliding smooth inside upper?
Pressure from the round in the mag slowing the carrier?
Buffer tube binding on spring or buffer?

Does everything cycle by hand properly / carrier slides smooth and ejects round and loads another round? If everything cycles by hand smooth it is more than likely not getting enough gas and the problem lies with the gas tube or gas block.

What ammo or load? My 8.5" 277 Wolverine with 0.67 gas port required pretty hot loads to lock open on last round. Ran great supressed.

Try loading one round in a mag, firing it and see if it locks back. If not it is short stroking.