Ammo......2 3/4" Federal Premium 00 Buck As fast as I could pull the trigger.....All 12 rounds down range without a stoppage. The mag rocks in the magwell quite a bit. I'm sure it has something to do with making a mag that will fit all Saiga's. But, it seems excessive. If you look inside the ejection port with a loaded mag in the magwell, you can see that there is a lot of room for error with how the bolt face contacts and feeds a round from the mag. So really not a big issue and the drum worked great.