I've tried four different caps on the slix shot nipples (CCI 11, REM 10 and 11, and RWS 1075). I use a revolver capper and straight line capper in testind. All worked just fine, none fell off before firing, no failures to fire using just capper pressure to place them, and the only ones that might have caused a cap jam - due to the fact that they pretty well disintegrated - were the RWS 1075s