Gun won’t cycle

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Brettpep55
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Gun won’t cycle

Post by Brettpep55 » Fri Sep 20, 2019 5:49 pm

I have a 300 blackout AR pistol with a7.5 inch barrel. When I initially built it I did not have cycling issues. It started a week ago it would no longer cycle sub sonic rounds. Now it won’t cycle any rounds. Looking as to what the issue might be?

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bugs1961
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Re: Gun won’t cycle

Post by bugs1961 » Fri Sep 20, 2019 6:01 pm

Possibilities:

Gas block loose and shifted
Gas tube obstruction
Worn out piston rings on the bolt
If the BCG isn’t disassembled regularly, crud on the bolt and inside the BCG
Inadequate lubrication

Brettpep55
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Re: Gun won’t cycle

Post by Brettpep55 » Fri Sep 20, 2019 6:05 pm

I’ll try breaking down and cleaning the BCG. What would be the best option for cleaning the gas tube?

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plant.one
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Re: Gun won’t cycle

Post by plant.one » Fri Sep 20, 2019 11:09 pm

pull the gas block. check for a blockage at the port.

my first 300blk barrel acted like that - ran fine at first, but there was a nasty chip at the gas port in the rifling. was shaving copper. my gas port plugged completely.
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Brettpep55
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Re: Gun won’t cycle

Post by Brettpep55 » Sat Sep 21, 2019 12:32 am

Yea that actually makes sense. There are a lot of brass and copper shavings every time I shoot.

bamashooter
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Re: Gun won’t cycle

Post by bamashooter » Sun Sep 22, 2019 11:12 am

Brettpep55 wrote:
Fri Sep 20, 2019 6:05 pm
I’ll try breaking down and cleaning the BCG. What would be the best option for cleaning the gas tube?
Normally there's no need to clean the tube. It self-cleans. Some folks will "swab out" the tube port on the gas key but I've never seen the need. Of course an obstruction can occur but that's not the norm.

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wildfowler
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Re: Gun won’t cycle

Post by wildfowler » Sun Sep 22, 2019 2:32 pm

When you take the gas block off, you want to see a clean circle of soot all the way around port which would indicate proper alignment.

They can be tricky to get properly aligned.

I also like to make sure the gas tube itself is as free floating through the receiver as possible. I don’t know if it can become an issue with the proper functioning of the bolt carrier or not. But I like the tube to literally rattle around freely and not be in a bind against one side of the receiver hole that it passes through.

When you put the gas block back on put a little bit of blue Loctite around the edge of the underside of the block to help seal it off.
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