I was going to build one of those but decided to build a 357 Automag instead. The problem with the 375/38-40 was the bullets. Not too many available. Also you have to make another barrel. With the 357 Automag, I had the barrel rebored to 357. Then got a set of dies to make the ammo. Sent some ammo to Clymer and had a reamer built. The face of the carbine bolt had to be opened up for the larger base and an extractor modified. I later found that the extractor from the the Universal Vulcan 44 pump carbine would work better than the modified stock one. I lived in Ft. Lauderdale and Universal was still around. I ended up with a carbine that would give a 158 gr jacketed bullet 2000 fps, a useful gain. Had to drop the 357 Automag loading data by 10 percent to get a useable load. The 15 shot mag held 7 rounds and the 30 shot held 14 rounds. No mods to the mags or feed ramp was necessary. Accuracy was excellent. The scope mounts available then were a problem as the brass would hit the scope. Now we have a forward scope mount that replaces the handguard so that would work well.