[GarrettJ]

I keep toying with the idea of using a USP for USPSA. I've got a number of 16-round mags and a jet funnel. However, that is still somewhat limiting, when I've got other guns that hold 20 rounds in a 140 mm mag for that sport. Some have said they had shoehorned various aftermarket Glock basepads on the HK mags with some success.

I'd read here previously that Bruce Gray had been converting STI mags to work in the USP. I tried one of my STI .38 Super mags, and it fit just fine. If I wanted to convert a mag, would it be as simple as taking an STI .40 mag and cutting a catch in the appropriate place? Other than typical mag tuning, is there anything specific to converting one of these to work in a USP?

 

[brutetc]

I would expect the follower in the STI would need to be modified, but I don't have an STI mag in front of me to look at. Will the STI magazine lock the slide open?

-Sean

 

[GarrettJ]

I would expect the follower in the STI would need to be modified, but I don't have an STI mag in front of me to look at. Will the STI magazine lock the slide open?

I'm not terribly concerned about the slide locking open. If you shoot to slide-lock in USPSA, you're not planning your stage well, or it's not going well. Half of my match guns have the slide stop disengaged anyway, so it's a non-issue there. As for functionality, as long as it feeds the last round correctly without interfering with the slide, it should be good to go. Good detail to be aware of though.

 

[brutetc]

I'm not terribly concerned about the slide locking open. If you shoot to slide-lock in USPSA, you're not planning your stage well, or it's not going well. Half of my match guns have the slide stop disengaged anyway, so it's a non-issue there. As for functionality, as long as it feeds the last round correctly without interfering with the slide, it should be good to go. Good detail to be aware of though.

Good point, most of my competition shooting involved wheel guns and rifles, so I haven't had to pay attention to magazine reloads, just grab a second gun

-Sean