Need help- AR-15 is now single shot

[WBAR]

The other day I turned one of my fully functional ARs into a single shot (no ejection of spent case or cycling of action) after replacing the GI handguards with Magpul MOE ones. No, I did not move the low-profile front sight block in the installation process. A cursory inspection by my gunsmith indicates I did not pinch the gas tube. The AR is a Bushmaster lower with A2 buttstock, ATI upper (M4 configuration), and ST bolt group (truck gun). Ammo used was Federal 55 gr. FMJ & Independence 55 gr. FMJ. I've switched out the bolt carrier group for another try tomorrow. Any other thoughts? Thanks, Bill

[bsoileau24]

Did you check the gas rings on the bolt?

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[Righter13]

The other day I turned one of my fully functional ARs into a single shot (no ejection of spent case or cycling of action) after replacing the GI handguards with Magpul MOE ones. No, I did not move the low-profile front sight block in the installation process. A quick inspection by my gunsmith indicates I did not pinch the gas tube. The AR is a Bushmaster lower with A2 buttstock, ATI upper, and ST bolt group (truck gun). I've switched out the bolt carrier group for another try tomorrow. Any other thoughts? Thanks, Bill

if you have an Air Compressor you can blow air down the chamber and tape off the muzzle and see if the air comes through the gas tube.

[_Stormin_]

Pics would help to try and fix this quite a bit. The more concerning thing is that you've had a smith look at it and they could not diagnose the problem...

[Ryno12]

Obviously there's an issue with the gas system. Check the gas block alignment, tube, etc. This should be a simple fix.

[WBAR]

Gas rings look good, but I've also changed out the complete bolt carrier group and will retry with the new assembly tomorrow.
Gunsmith just gave it a cursory inspection (not in detail); any thing more will cost me a $40 shop charge.
Next step will probably be to remove the MOE handguards and try it if the new bolt carrier group fails to correct the problem.

[Swag]

Is the gas block pinned or screw/clamp? If it's screw/clamp, you may have canted the gas block during the handguard installation.

[Kenneth]

Is the gas block pinned or screw/clamp? If it's screw/clamp, you may have canted the gas block during the handguard installation.

Has to be something like this.


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[WBAR]

Thanks, guys. The block is held by two hex screws which seem to be very tight, and the block looks straight. But this is something that I need to have checked.

[rushca01]

Thanks, guys. The block is held by two hex screws which seem to be very tight, and the block looks straight. But this is something that I need to have checked.

Make sure it's not sitting directly against the ledge on the barrel. There should be a 1/16 gap give or take.