Help:AR short stroking

[Throat Erosion]

I have a Bushmaster XM15 E2MS, it is a A3 flat top with a 20 in bbl, and I have been having problems with it short stroking. After the charging handle is pulled all the way back and dropped, a round is chambered, then it fires fine. The bolt carrier goes back and the shell is ejected. However, the bolt carrier doesnt go back far enough to get behind the next round in the magazine and chamber it. So consequently the bolt slides back forward without the next round.

I have tried many different types of ammunition(handloads, factory loads, 45gn, 55gn, 68gn,ect) I have also tried different magazines and replaced the gas tube and I have still been having the same issue. It has also been cleaned and lubed(not over lubed though) and I have still been having the same issue. Does any one have any ideas or suggestions for me?

I tried to give as many details as possible but if you have any other questions feel free to ask.

Thanks

[Byte Stryke]

Gas leak
Check rings by doing "The Stand"
with the BCG out of the receiver, Extend the bolt to the end of the stroke, Stand it on end, see if the BCG Collapses. If it does, need rings
Check Gas tube alignment/Damage
Excessive carbon Under hand guard near the gas block

beyond that... take it to Bert at BP tactical for a look over.

[Throat Erosion]

I forgot to mention that I did check the gas rings and realigned them a few different times and ended up just getting a single ring from midway usa so i didnt have to worry about the alignment of the three and it still continued.

[Marlin]

Check the gas key on top of the bolt carrier. Make sure both screws are tight.

[mc223]

Lubricate with Automatic Transmission Fluid.

I forgot to mention that I did check the gas rings and realigned them a few different times and ended up just getting a single ring from midway usa so i didnt have to worry about the alignment of the three and it still continued.

Lubricate with Automatic Transmission Fluid.

Although these Mcfarland 1 piece gas ring sounds like a great thing they really are not. They do not expand into the carrier reliably and do not last long.

Lubricate with Automatic Transmission Fluid.

If not kept at the fringe of over-lubed they will drag heavily and cause an excessive delay of the BCG, which will behave as a short stroke.

Lubricate with Automatic Transmission Fluid.

Use the 3 ring OEM setup for better results. Even if the rings become aligned there should not be enough gas leakage to cause a SS condition.
A GI will not be stopping in the middle of a firefight the check the gas rings aren't aligned.

Lubricate with Automatic Transmission Fluid.

[Kaiser.Shooter]

My buddy has the same carbine and had the same short stroke problem.
After 2 times shipping it back to Bushmaster they finally resolved this issue by drilling the bigger barrel's gas port.

[Great-Kazoo]

buffer and spring passed muster?
oh yeah toss that 1 pc ring.

[henpecked]

Primer lodged in the gas key?

[Throat Erosion]

I will start looking into those things. But it is hard to test things without firing so i will start making a checklist of things to do next time i get out. Keep the ideas coming and i'll see what i find out.

Does anyone know what the gas hole size should be, coming out of the barrel into the gas tube?

[Kaiser.Shooter]

I would try first to clean the gas port and the gas tube.
Pour into the gas tube some carbon remover, let it seat for 1-2min and purge with compressed air right into the gas tube, after that clean the bore.