Slide locking back with loaded mag

[weemsf]

I have a P07 in 40 S&W.  It has had maybe 500 rounds through it.  Super accurate, but it has developed a new problem.  While firing it will occasionally lock the slide open with a loaded mag.  Drop the slide using the slide stop, fire again, and it may or may not lock open on the next round.  Any ideas?

[painter]

Different ammo?

Some bullet shapes could possibly hit the slide stop.

[Cesar]

Most likely bullet is hitting slide stop inside frame due to either: 1) bullet shape/OAL; 2) weak mag springs allow rounds move forward during recoil and then bullets hit slide stop.

Also, your thumb may 'flick' slide stop up while shooting - check your grip.

[weemsf]

Practically new mags and locking open with three different shooters.  Made sure my thumb was not hitting the slide stop.  Ammo shape should not be a concern, as I was using 165 grain truncated cone Berry's bullets.