It's a "European style" Heel release.
Good news is you are very unlikely to accidently loose the magazine, or inadvertently dump it.
Bad news is it takes two hands to remove magazine, and you can't do multi-tasking 1 sec reloads. Just the inherent nature of the beast.
If you absolutely positively need to have rapid continuity of fire, tou need Two P64's, and execute a * Warsaw Reload * .