2nd Glock that doesn't stay open.

[Member 5605]

Just cut the thumb off.

 

[Kruel J]

Its really quite common. I've actually seen it more than once with right handed shooters. Since I shoot left, I have no experience with slides not locking back. I grip thumbs forward and honestly just a bit off the gun as well. Try floating your thumbs as they aren't really necessary to grip the gun anyway.

 

[pinne65]

Ok - it's confirmed, keeping the thumb of the slide stop while firing the last round will allow the slide to stay open. Just got to learn how to count down from 16 & 11 now.