I bought my first handgun a couple of weeks ago, a Walther P22 tactical (5" barrel). The 22 LR is an inexpensive way for us to get a lot of practice. My son and I took it out to the state range yesterday for the first time. After about 50 rounds the slide stopped staying open after the last round is fired. We were at the state range in Sweet Valley so we were firing 5 rounds at a time. I was using CCI mini mags. It never jammed or misfired but by the end of the 100 round box the slide was never staying open after the last round was fired.

I'm not sure if this is a problem with the gun or the ammo. We bought it at Cabella's in Hamburg. I don't want to make the 90 mile drive to find out it's a cockpit error on my part or something to do with the ammo I'm using. Any thoughts?