Frank, everything I'm seeing doesn't show it includes a buffer. It Should work fine with any milspec lower and buffer/spring. It Should have included 3 choke tubes though. Most semi automatic shotguns require a break in period to work out all the kinks before it'll cycle 100% reliably. Before buying anything else I'd recommend running roughly 100-150 rounds through it and giving it a good clean/lube after. I've read a few people having feeding issues with certain ammo due to the magazine. If that turns out to be the case I'd recommend contacting the manufacturer. You can contact them at (844) 432-4867 or you can email them at (internationalfirearmcorporation.com). Sorry you're having trouble but hope this helps some.

Hi Frank, the supplied buffer is fine. The stiff spring is the issue. Lock your bolt back for 48 hours and try your shells again. You'll be surprised. Also, Buds state that they do not open factory sealed Firearms etc, so I would contact IFC Customer Support to get first hand information on exactly what should have been included (by UPC code) and they should be willing to get you accurate info and replacement chokes if they were missing at : https://internationalfirearm.com/ -- Cheers and stay safe!

Frank, from what I'm reading, it should work with a standard mil spec buffer & springs. People with custom lowers will have issues if the buffer and spring are different from standard Mil Spec buffer and springs. If you have mil spec buffer, I would try a higher velocity shell. As far as the choke tubes, it looks like they should have been included also. I would contact the manufacturer to see about getting some sent your way, the info should be in your user's manual. Good luck & have a great weekend!