If you start experimenting with prototypes, I think you'll find the VG1-5 operating system to be a disappointment. The whole gas chamber thing is about as useful as the Blish lock system in the early Thompsons. The VG1-5 will work just fine with a non-perforated barrel, just acting as a blowback action. It won't work well for heavier calibers, though - for that you would need to delay the bolt with something like the rollers that the Germans were developing at the same time.
Another issue you may find is that a straight magazine well combined with the recoil impulse will put a dent in your magazines.
Another issue you may find is that a straight magazine well combined with the recoil impulse will put a dent in your magazines.
