I just got to test one of the ProMag drums today -- sorry to say this one didn't work worth a darn. This drum came from the SHOT show and I don't know if it's a prototype or not. I tried Remington bulk ammo, regular Remington, Federal and some Winchester ammo in it and I might get two shots in a row (if lucky) and then jams -- lots of jams -- this drum did not want to really feed anything. I paid attention to not allowing the rim of the round being loaded to slip over the rim of the previous round. This is not my drum mag so I could do no adjustments or mods to it -- only load it and try to shoot. I have two 10/22's and the drum acted the same in both. I even tried some Remington Viper ammo to see if the tapered bullet would help it feed but not luck. By the way, the feed lips are plastic. The picture below shows the feed lips on the drum mag with a stuck Viper round. When loaded the rounds mostly sit level and kinda nose down when the bolt tries to pick them up.