A simple -5 Rounds limiter for the Ruger BX-15 magazines, as used in the Ruger 10/22 and others.

Semi-auto rifles are restricted to 10 round magazines here in Germany for competition use. Rimfire magazines are generally not restricted, so larger capacities are readily available. I wanted to use my Ruger 10/22 with the BX-15 magazines instead of the stubby BX-1, which are a pain to reload under time pressure (e.g. for the “BDS Mehrdistanz” discipline), as they sit flush in the rifle.

I previously used cut down .308 cases with electrical tape around them, to achieve the same effect. But since I now have an X1C, I decided to design a proper limiter and print them. I included the F3D file, in case anyone wants to adapt it (e.g. to the BX-25). The thickness might be reduced by a tad still (could also be reduced in the slicer if you don't want to mess with the design), but I wanted to err on the thicker side, to ensure that the limiter is firmly held in place and doesn't shake around (would probably not hurt function, but annoy me).

Installation is easy and can be done in a matter of seconds. Just remove the two screws, separate the two halves (no spring tension, so nothing should be coming flying out). Add the limiter into the bottom of the left half with the markings facing up (see pictures) and assemble the magazine again.

I designed it in a way that the 11th round can still compress the stack about half or ⅔ of the way, but it can't be pushed under the feed lips. This should allow the fully loaded magazine (with 10 rounds inside) so be comfortably be loaded even on a closed bolt, since the stack of cartridges can be compressed. This is especially useful, since the 10/22 does not have a last round bolt hold open and most reloads would be done on a closed bolt.

I printed the test prints in PLA with the 0.4mm nozzle and 0.28 Extra Draft profile on my X1C. The final versions I printed in PETG with the 0.4mm nozzle and the 0.2 Strength profile, again on my X1C. Honestly, pretty much any material and profile should work. This is not a laod bearing part in any way. Since there is no downward spring tension in the BX mags (the coil spring attaches to the top), it's basically just chilling there at the bottom of the mag and not doing anything.

This is my first published design. So I'm happy for any feedback :)