I made a lot of 410 shotguns on the standard SMLE rifle. Simple matter to bore and ream the barrel leaving in a degree of choke and chamber for the 3" 410 cartridge. Although the magazine stays in place the 410 won't feed from the mag but a single loaded cartridge will just drop in and chamber easily. The empties extract and eject perfectly. Remove the rear sight and replace the front blade with a bead and good to go. The bored out barrel lightens the SMLE up nicely and makes a slick and strong little gun with a good safety either on the bolt as Caprivi's gun has or left side of action for the latter model SMLEs. They usually threw a nice pattern and with the 3" shell were good little killers.

We cut our teeth on these as kids using them on ducks and rabbits and got more than a few goats at close range with the 410 slugs too. My father before me made them up and I learned from him and carried on the gun work.

I don't know why Caprivi's 410 has a long bolt action, the standard SMLE bolt and action made for the 303 British cartridge is plenty long enough for 3" shells. Very nice collectable though.