I own and Inland Marine and a Saganaw Gear carbine. One, the Saganaw Gear, is like new. A buddy of mine bought it in the 1970's for $20 plus shipping. I have the paper work. It's the Korean model with the bayonet lug. The other is the Inland. It was a San Quentin guard gun and has no bayonet lug or finish, but it shoots a bit better.
People claim that M-1 carbines are not accurate. That has not been my experience with these little rifles. Nor do they kick. My grandson who was uncomfortable shooting the AR15 loved shooting the carbine. I do too.
Get a military one. They are around. Figure $600 to $800. Yeah they are "spendy" (as we say in Oregon) but a lot of fun to own and shoot. Oh, don't go bear hunting with one. However, I had a friend who carried one in WWII. He said that during the War all of the GI's were exclaiming how they wanted one to hunt deer with. He brought one home and immediately shot a black bear...and her cub! Their skins adorned his den wall.
Concerning the magazines. The 30 round ones, in my experience, jam. I only load five in my 15 round mags and they shoot out. They do with 10 too.