A friend of mine is an armorer for sig .. and a collector. He acquired a KP-31 ten years ago that had never been fired. His is not totally Finnish .. evidently in the 1930’s Birmingham Small Arms manufactured many of the barrels for the Finnish company that I cannot remember or pronounce their name.
According to my friend it was and still is the most accuatate sub machine gun built. Unlike the infamous UZI’s of our day, ther are no stamped steel and spot welded parts. Everything including the breech was machined steel.
Recoil was controlled by not putting the butt to the shoulder but allowing the fore thumnb on the forestock to carry the recoil while the butt of the gun was pulled in tightly to the chest. It allowed for a recoil to be absorbed in a straight axis, relative to the shooter, which accounted for its accuracy.
I was amazed at the simplicity of the gun .. simple to strip down and field clean .... I would love to have one myself.
Oh .. and the Finn’s ... they were a force to be reckoned with. We have drive by shooters .. they had “ski by shooters” that drove the USSR nuts and kept the fear level high amongst the soviet troops. Nobody wnate to be stationed in that region.