I have put 30 to 40 of the 20ga BuckHammers through my 20ga USH and have never had a FTF. My USH is on the frame the barrel came with from the factory, not a fitted barrel, if that makes any difference. The ammo was bought from 3 different places so I doubt they are the same batch or lot #. I have shot the BuckHammers out of my 12ga Turkey barrel with a rifled choke tube. That barrel is factory fitted to a .223 frame. I think I have shot about 40 rounds out if it without a bit of trouble other than a sore shoulder.