The problem in using any shotshell in a firearm with a rifled barrel is the very rapid dispersion of the shot pattern. At a very short distance past the muzzle the shot charge is rotated out of any useful pattern. Shotshells really are meant for guns with smoothbore barrels. It might work all right if you load your shot charge into a capsule, and then into the cartridge, but you wouldn't be able to put much in a cartridge like the Nagant. Doesn't hardly seem worth it.