When I first purchased my 457, I bought two longer magazines that the seller assured me would fit. I think they held 10 or 12 rounds and were made for a rifle.
Anyway, I got them home and it was a week or more before I could try them out. They wouldn't stay in the gun! I could hold them up with...
FWIW, my opinion is that having a large number of bullets at your disposal would be the most important factor in a Paris scenario.
The main purpose in firing back would be to interrupt the attack. Faced with shots coming from the crowd, the attackers would no longer be able to stand there...
I bought a 457 years ago with two, 7-round factory mags. I also bought a couple of longer mags (maybe 10-14 rounds?) But they wouldn't stay in the gun when full of ammo. They popped out, seemingly at random.
I'm not sure what I bought. Maybe they were made for a rifle.
Anyway, since my...