How to Convert a 20-Round Sten Magazine Back to 32-Rounds

The plastic magazine that came with my MasterPiece Arms 930SST “Mini” MAC 10 did not allow for proper feeding. It jammed after the first or second round. I needed more spare magazines, and I wasn’t going to try the plastic ones again.

Centerfire Systems (at the time) was selling a 10-pack of 20-round Sten mags. They were about $4 after shipping and a post-3% credit card surcharge fee. A single 32-round magazine was about $24 before ship and cc fee.

The 20-round magazines were allegedly converted by the Israelis to increase reliability in sandy conditions. Sten mag production during the war also covered a huge quality assurance spectrum. One of the reasons I wanted to buy a 10-pack of cheap mags is so I wouldn’t feel bad about junking one that wasn’t 100%.

The conversion involves four brass rods inside of the magazine well. The lower part of the rod is bent around the bottom part of the magazine. The top part of the rod is pressed into the top part of the magazine. In order to remove the rod, you snap off the bottom “hooks” and then drill out the top part.

I tried using a punch, and it wasn’t easy. I recommend you use a drill.

Here’s how I do it.

About the Author: Short Barrel Shepherd

Short Barrel Shepherd is a regular guy and works to make Web sites and mobile apps easier for people to use. He spends his free time attending fight-focused firearm, knife, and combatives training, motorcycling, writing, and playing games. His daily carry is a Glock 19 pistol and an AR15 .300 Blackout pistol in a backpack.