Help! 7.5 won't cycle

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

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CES76
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Joined: Mon Dec 13, 2021 4:18 pm

Help! 7.5 won't cycle

Post by CES76 »

I just built a CBC 7.5in pistol. However, I can't get it to run at all. It fires one round and jams, FTE everytime. I'm using Aquila 150gr FMJ's. I did swap a buffer spring and buffer from a 5.56 gun and at least that did eject the spent round, but didn't pickup another round from the mag. This gun is really undergassed. Any suggestions to help fix this would be greatlly appreciated!
CES76
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Posts: 4
Joined: Mon Dec 13, 2021 4:18 pm

Re: Help! 7.5 won't cycle

Post by CES76 »

Also, it has a Hanker brake on it instead of a standard A2. It’s a CBC industries upper.
ReadyAimDuck
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Re: Help! 7.5 won't cycle

Post by ReadyAimDuck »

How confident are you that you properly aligned your gas block?
CES76
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Re: Help! 7.5 won't cycle

Post by CES76 »

The upper was all complete. I just built the lower
CES76
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Posts: 4
Joined: Mon Dec 13, 2021 4:18 pm

Re: Help! 7.5 won't cycle

Post by CES76 »

CBC is saying that the Aguila is sub par ammo. Wants me to try a “name brand” to see if that corrects it. Who knows at this point
ReadyAimDuck
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Re: Help! 7.5 won't cycle

Post by ReadyAimDuck »

I'm not familiar with that ammo, but I would expect a properly assembled rifle to cycle factory supersonic 150 grain ammo to at least some extent. The fact that it cycles none of it leads me to suspect that something is off or out of spec.

I could be wrong. I freely admit no knowledge of that ammo, or 7.5" pistol uppers. I do think it's a good idea to try other ammo as a troubleshooting step, but I have a hunch that something is less than ideal in your gas system or buffer system that you want to address if you want that set up to run reliably.
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