New build malfunction

[hlee]

I recently put together a 300 blackout pistol and just finished my first outing with it. The upside is that it is precise- at least as precise as I am with a red dot sight. The downside is that it is a single shot. I was using Sellier & Bellot 124 gr fmj loads and the gun would not eject. Loading single rounds in a magazine, it would fire and extract, but would leave the spent case on the follower of the empty mag. The gun locked back on the empty mag. It would extract and eject unexpended rounds without issue. I also noted that the primers were somewhat flattened and many were partially pushed out of the primer pockets- not enough to readily see, but enough to feel. No, I did not try any other brands or loads of ammunition.

Pistol gas system
Nonadjustable gas block
Heavy buffer
Ballistic advantage 8.5” barrel

What say you? Overgassed? Bad extractor? Bad ammo? Other? I can get pictures tomorrow. Let me know what you need to see. Thanks.

 

[hlee]

I should know better than try to post with an iPad, I thought I was in them semi auto forum. If a mod sees this, can you please move this to the correct forum? Thanks.

 

[Sniperstud]

I've heard S&B can be a little hot, but I haven't used it.

Try a different brand of ammo. Stay with supers, so you'll be comparing apples to apples, more or less. If you have similar issues with the new ammo, Strip your BCG. ​

Remove your extractor and make sure you have an undamaged spring and O-ring present. If either the spring or O-ring is damaged or missing, replace them. Check ejector function to be sure it moves freely and doesn't feel gritty. If you have the tools, remove the ejector. Clean the ejector, spring, and their corresponding hole in the bolt. Lubricate when you reassemble.

 

[Apnea]

Is the extractor grabbing the case rim?