none of the 308 mags are going likely work for a 410 at they are designed with ribs or get narrower in the front to properly hold a necked down 308 round.
I stuck some 410 shells in a fal mag and it not a very good solution.
Im going to be using G3mags on my switch barrel build and i likely will just bend up a square non ribbed box that will take a g3 spring. a double stack 410 may be tough but not imposable if they can get 7.62x54r to feed then it can likely be dont for the 410.
Im likely going to go rimless and avoid those problems and be able to use the G3 follower.
as single stack would be a easier way to go. orpossably just use Sagia mags but there way to pricy IMOO.
I think you really better think about buttin the upper shroud on the barrel to gide the round. it coing to be pretty tough to feed a flat shell into a hole that is only a few thousands bigger with just a bullet guide.
You might be able to press on a shroud onto the barrel by reducing the part that sticks through the reciver and then add the shrouds/ guides that wayif your working with a prechamberd barrel.
I have like 15 barrels to build before I worry about a shotgun barrel. then Im going to do a smokeless powder 458 cal muzzle loader barrel for it as well A 60,000 psi 458 cal smoke less powder muzzle loading ak will be that badest AK round yet at least for one shot. Oh yea they allow muzzel loader in my pistol/ shot gun zone.