AR build short stroke problem

D_behrnes · Nov 17, 2017

Hey y’all I’m having an issue with one of my latest AR builds. My bcg continuously short strokes and I can’t seem to figure out why, maybe somebody on here can shed some light on the situation. I’ve tried using numerous brands of ammunition both .223 and 5.56 and nothing is functioning better than others. I’ve put this bcg in 5 of my other functioning rifles and it still short strokes. It’s so bad that It won’t even begin to eject the cartridge. Any ideas that could help me out here??

DaSouthernYankee · Nov 17, 2017

Have you checked the gas key? It could be loose, causing gas to escape outside the carrier. Also it could be worth checking to make sure there are gas rings on the bolt. Sounds stupid but stuff happens.

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dougstump · Nov 17, 2017

Here's a few thoughts:
1. The gas passage from the key through the carrier could be blocked.
2. Missing or really messed up piston rings.
3. Carrier is out of spec where the bolt slides in.
4. Is the key properly installed, tight with no evidence of gas leakage around the joint to the carrier.
5. You could try installing a known good bolt into the suspect carrier and see what effect it has.

Take the carrier group, pull the bolt all the way out. Gently set the carrier down vertically on the bolt. It should stay up, if not check the rings.

Here's a real "shot" in the dark. Clean the recess on the right side of the carrier with alcohol, then place a piece of masking tape to cover the two gas relief holes but stay within the recess so it won't interfere with the bolt movement. Load and fire one round. Is the tape still there? If you've got gas going through the carrier like it's supposed to, but leaking past the bolt, I'd expect the tape will be blown off.

Wish you were closer to Shreveport, I'd be happy to look at it for you.

topgunz1 · Nov 17, 2017

So that BCG causes problems in your other functioning rifles? sounds like it's a problem with the BCG, not the gas or buffer system. Check the extractor spring. I had a budget BCG that had a horribly weak spring, it caused no end of problems.

rcm192 · Nov 17, 2017

topgunz1 said:
So that BCG causes problems in your other functioning rifles? sounds like it's a problem with the BCG, not the gas or buffer system. Check the extractor spring. I had a budget BCG that had a horribly weak spring, it caused no end of problems.

Same here. I installed a MGI Dfender oring. It helped out alot. Extraction problems went away. Even with cheap steel in my 7.5" sbr. now all of my ARs have this product.

D_behrnes · Nov 17, 2017

I didn’t think about the o-rings I’ll have to take a look in the morning

D_behrnes · Nov 17, 2017

dougstump said:
Here's a few thoughts:
1. The gas passage from the key through the carrier could be blocked.
2. Missing or really messed up piston rings.
3. Carrier is out of spec where the bolt slides in.
4. Is the key properly installed, tight with no evidence of gas leakage around the joint to the carrier.
5. You could try installing a known good bolt into the suspect carrier and see what effect it has.

Take the carrier group, pull the bolt all the way out. Gently set the carrier down vertically on the bolt. It should stay up, if not check the rings.

Here's a real "shot" in the dark. Clean the recess on the right side of the carrier with alcohol, then place a piece of masking tape to cover the two gas relief holes but stay within the recess so it won't interfere with the bolt movement. Load and fire one round. Is the tape still there? If you've got gas going through the carrier like it's supposed to, but leaking past the bolt, I'd expect the tape will be blown off.

Wish you were closer to Shreveport, I'd be happy to look at it for you.

Will definitely go through the checklist in the morning hopefully one of these will help me out. Thank you

AR build short stroke problem

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