Bottom line up front: we recommend that all S15 users upgrade their pistols with to a metal mag catch, either ours or someone else’s that is properly made. Here’s why.
First off, the proper term is mag catch, but we won’t complain if you call it a mag release (clip anyone?). S15 mags are of course made from steel, and Glock mag catches are made from polymer. This combination is potentially problematic for anyone who plans on actually using their pistol for more than an Instagram prop.
The mag catch serves a few different purposes: it secures the mag in the frame of the pistol, but it also holds the magazine in the proper position within the frame. This is an important distinction. If the magazine sits too low or too high in the frame, the slide either won’t reciprocate, or rounds will not reliably strip off the magazine and feed into the chamber.
Steel being harder than plastic, eventually using S15 mags with a plastic catch will cause feeding problems. How long this will take depends on a bunch of different factors, most importantly, your specific gun and how much you shoot. We have guns with plastic catches with many hundreds of rounds that are still functional, but some customers report excessive wear after just a couple hundred rounds. Feeding issues also seem to occur much faster in early gen 1 (silver slide) guns with plastic catches vs. gen 2 (black slide) guns because of the differences in the frames.
Since we can’t predict when your plastic catch will wear out enough to cause you issues, we are taking the safe route and recommending that you swap out the plastic catch for an aluminum catch. We make one that works great, but there are also other options on the market, and while we haven’t tested anyone else’s catch, presumably they work just fine.
It’s not an expensive part to swap out, and the peace of mind is worth it.