There are two basic models of this Russian shotgun available in the U.S; one with the basic AK patterned fixed stock, the other with a welded open folding stock. In order for these to have been imported into the U.S the BATFE required the stock to be welded open making it one piece with the receiver.
The moment you break the weld (which is a very small spot that can be easily dremeled) you create a new non-U.S made part. You then would have to replace and or add U.S made parts to make the Vepr 12 922r compliant if you wish to have the original Russian folding stock operational.
Some people disregard the 922r law because of the belief that “no one really checks”, but keep in mind that if your gun is ever stolen, or used in a case of self-defense, anything that could possibly involve police custody of your firearm, even for a short while, then there will be problems if your gun is non-compliant.