AR feed malfunction

[MistWolf]

That definitely sounds like short stroking. Verify with a lock back check using full power ammo, then start looking for the leak/blockage .

[26 Inf]

Gas system - gas tube, carrier key, rings, receiver extension, spring, buffer

even though it works with another BCG

do lock back test - with a couple different mags - USGI and poly

check to make sure gas tube is installed correctly into gas block

shotgun upper and remove BCG and charging handle - see if BCG slides onto and off of gas tube, then do it with the charging handle in place

inspect BCG - carrier key, use gravity test for rings

check spring - a to insure it is the correct spring for the RE - carbine should be 10.5"

reinstall buffer and spring, insert BCG and close 'er up, lock action to rear, let bolt go forward - does it go fully into battery - check by pressing forward on the concave portion of the BCG. If it didn't go into battery we need to figure that out

Bring BCG slightly to rear with charging handle, insert index finger and gently ease the BCG forward, then press the charging handle all the way forward. Now, press the BCG all the way to the rear, you are feeling for any binding through out the carrier's rearward travel. At furthest rearward travel, press the bolt catch in and ease the bolt forward, check to make sure the BCG is retained to the rear by the bolt hear, not the carrier.

Due to the fact that I want the thing to function whether it is dry or lubed - I wouldn't lube the BCG as much as I normally do use.

That's all I got, if that doesn't drill down to what is wrong, I cross my hands over my man parts (outside the jeans) and look perplexed.

[Circle_10]

I had a gun shear a gas key screw once and turn into a single shot. I had a thread about it. The key appeared to still be on tight so I didn't think that was the issue but on the recommendation of Iraqgunz I checked the gas key screws more closely and using a Wheeler Fat Wrench to take the screws out determined that one had in fact sheared in half.

I've also heard of popped primers getting stuck in the gas key and causing gas obstructions.

[Lincoln7]

I'd check for gas block alignment and gap between gas block and shoulder on barrel (~.025"?) which accounts for handguard endcaps.

[Iraqgunz]

Don't be surprised if it's the garbage WMD NiB carrier.