[kalibr]

I have about 2k through my 9mm P99.  Zero mulfunctions until I started practicing "double-taps".  Firing 147 grain blazers in rapid successions has cause the slide to lock back with some rounds still left in the magazine on several occasions.  Subsequent slow firing didn't produce any slide lock-backs.

What gives?

Gun/magazine were well cleaned and judiciously lubricated.  Haven't tried other ammo.

 

[E.T.]

Maybe that during rapid fire and double taps your thumb unintentionally touches the slide catch ?

Let me know