M3A1 "Grease Gun" 9mm full-sized replica

The M3, better known by its nickname "Grease Gun," earned that name for an obvious reason — its simple stamped-steel tube receiver looked more like a mechanic's tool than a submachine gun. Adopted by the US military in 1942 to replace the more expensive Thompson, it traded polish for practicality:
cheap to mass-produce, easy to maintain, and effective in the hands of tank crews and paratroopers right through Vietnam. The M3A1 update simplified the design even further, dropping the separate cocking handle in favor of a finger hole in the bolt.

Check out the photos and video above to see the finished build — the tube receiver and folding wire stock come through clearly, staying true to the utilitarian look of the original.

This full-size replica brings that no-frills design to life in 48 printed parts, 5 metal hardware pieces, and a single rubber band for the action. A complete video guide for assembly is included inside the download archive.

— SPECS —
Length: 545 mm
Width: 50 mm
Height: 310 mm
Plastic parts: 48
Metal parts: 5
Rubber band: 1

Questions about the build or sourcing the hardware? Drop a comment — happy to help you get it right.

🎁 Get 25% off your next model! Post a Make of your finished, assembled build — photos or a short video, with a quick voice or text comment about how the print and assembly went — and I'll send you a 25% discount code for any other model in my collection. Just message me once your Make is up!

Material: PLA
Minimum bed size: 220 x 220 x 250 mm
Layer height: 0.2 mm
Infill: 40% (100% for small plastic screws/pins)
Max print speed: 300 mm/s