The SIG 310, aka MP48, is the final evolution of SIG's submachine gun design from the 1920s. It began as the MKM/P/S/O with a folding magazine well, wooden stock, and fancy lever-delayed operating system. Over almost 30 years of development, the wood stock and the lever-delayed system fell away, as did the really high quality finishing work. The folding magazine well and the magazine itself remained intact, however.

This final version is a very simple blowback mechanism with a similarly simple collapsing wire stock. It uses a 40-round double-feed magazine of 9x19mm ammunition, and fires at a zippy 1000 rpm. I was surprised by just how easily controllable it was despite the high rate of fire and short receiver - and also by the harmonic ringing of the wire stock when firing. While this may be an embarrassingly crude gun for the Swiss, it is a gun that most other countries would be quite proud of.