This is a magazine coupler for Gen 3 PMAGs to couple 2 10 round magazines together, intended for those living in stupid states. This does not extend the capacity of the individual magazines.
This coupler is under a lot of spring tension so print this with thick walls and lots of infill. So far 1.6mm/80% has held together without it exploding and shooting springs across the room. I am not responsible if this fails at any point in any way.
To decouple the magazines insert a small screwdriver or similar device into the slot in the back and rotate it to push up the individual magazine insert buttons, carefully sliding out that magazine. Remember, spring tension.
Monoprice Maker Select 3D V2
This is still a work in progress. If printed in ABS it seems to fit OK. If printed in PLA minor sanding was required in the coupler channels that slide over the bottom of the magazine due variations in material expansion characteristics. Sand the coupler, not the magazine.