Around WW2, Sweden decides that it's dangerous times, and they should buy some of these new-fangled submachineguns which people made so much noise over in WW1.
They buy some small smattering of things, some US Thompson guns (along with ammunition, because nobody made .45 Auto in Sweden at the time, and Norway, who actually used 1911 pistols as army sidearms, likely didn't have much production output left over for their neighbors), they also bought some subguns from Germany, but not a lot. So they look to their other neighbor, Finland, who have a pretty rock solid one, the Kp/31, as seen here
>>93975Getting in contact with Tikkakoski, they ask if they can have it to their specs, they want it in a bit of a different stock profile, sure, and a shorter barrel, alright, and they would prefer the 50rd quad-stack magazines instead of the drums, for the slimmer profile, alright, that can be arranged.
Also, they want it in the same caliber as their current service pistol, the FN 1903
>>101033Tikkakoski objects to this, because that means they'll have to set up special tooling for barrels and magazines in 9x20mmSR Browning, a semi-rimmed cartridge, which is a lot less easy to build a magazine around, even more so a double-stacked 30rd one, but here Sweden is asking for a 50rd one, a quad-stacked magazine, for a cartridge which can't really stack side to side in any particularly easy manner.
After a lot of "Please just buy it in 9mm Luger", they finally give in and get to work on making the damn things in this one caliber used basically only by Sweden and by Belgium.
Thus, what you have here is the Swedish m/37, a Finnish Kp/31 with a short barrel, funny stock, and a funny magazine. I'll point out that the 50rd quad-stack magazine as originally designed for 9mm Luger only worked kind of ok-ish, it's not nearly as reliable or sturdy as the simpler 36 round double-stack magazines, or the much more robust 72rd drum. I imagine reliability with these were never excellent.
