After months of reading and trying- good info here- I have this 1940 4 digit serial number ex cop Model 50 100 per cent. Most of the info to do this was from here with a few wrinkles.
The gun is about 95 % nicely finished and blued. Hard to believe she's 79 years old. In looking this was the best shape of any I'd seen.
Like was posted here, she must be kept clean I clean her after each shooting - 300- 500 rounds. The 20 minutes to do so is is well worth it.
Minimal lubrication is all it needs. I have been using a dry lube with just a bit on the ammo as well.
The original 12 round mags work fine BUT. the 22 round ones from Sarco made in Taiwan are ok too. I load them with just twenty for obvious reasons. Sarco has plenty and they are $65.00 each.
One thing which was a big help was an extra power recoil spring from Wolff. Got me from 90% to 100 % functioning.I think that because the bolt is so light it needs that extra push.
I have 4 30 round mages from Keystone.Only one works. I could not figure out why but I have two ideas. Back in 1940, there were plenty of submachine guns with 30 round magazines, The TSMG later on, the MP 40, Suomi, Lanchester. BUT MOST WERE SLAMFIRE GUNS with much heavier bolts. I'm thinking that' why they never developed a 30 round mag for this gun.
It's easy to see that the M 50 is not as heavily built as the TSMG. But it is several pounds lighter too, and much cheaper, in 1940 and for us.
It is not a combat gun for the dirt, mud, etc. But for us who can keep them clean on the range they are fine. Mine is 100 % with 3.9 of Red Dot and a 230 RN plated bullet. That is about half the pressure of the GI load. Good I think for this lightly built gun.The ROF still up there- really can't get less than a three shot burst off.
It breaks a firing pin every 500 shots or so but I will shorten one and hopefully fix that, too. Comments welcome