Nice FN high power. Congrats. Have a hi power that an uncle in 4th Inf Div brought back.
If your WWII hi power slide locks back occasionally with one round still left in your magazine, you should probably replace the magazine spring. This was a problem I had back when I first started shooting my hi power back in the late 1960s. Chuckle, problem went away around 5 years ago when I replaced the magazine spring.