A lot of good comments, pictures, and opinions.
I wasn't aware of the M2 catch. Worth looking into. I have two USGI 30 round mags that feed fine, but I appreciate the comments about the 15 rounders. I have two other carbines, a Saginaw and an Inland. Those had mostly original parts, so I'm leaving them alone.
I love the original look as well, but for home defense, I wanted something with a bit more versatility than the original USGI version. At night, a good 125 lumens flash light beats a bayonet, red dot sight beats the original iron sights, and the folding stock helps in tight spaces. The 30 round magazine gives enough firepower, you probably won't need to reload. I agree the original one is pretty darn tactical to begin with, but it can still be improved for indoor and night use. I do agree the added weight from the folding stock, 30 round mag, and added extras is not a plus.
As a collector of Swedish Mausers, a collectible is something that is matching down to the firing pin, so I was a bit surprised by the strong feelings about what I consider to be a parts gun. To each his own, I guess. I feel no remorse at converting this one into its present form and I am willing to suffer the wrath of the carbine Gods if I brought bad JuJu on myself.
I'm still puzzled by the discussion about .357 magnum. Has ANYONE run that round through a carbine? Does it cycle, is it safe, is it accurate? It would offer some additional versatility for home defense ammo, IF it is suitable.