Ok, I did some more looking around. I found that the base diameter for a 410 is actually .469 and you can use .444 marlin brass for reloading! The actual end bore diameter would change depending on the choke used. Most are full and some are modified.

You are correct that most of the slugs used are between .387 and .415 in diameter. I do believe a .45 bullet will work though. It is simular to having a .357 that will fire 38 and 9mm rounds as well. I believe most barrels are actually smaller than the bullets they fire. I'm not that up on reloading though.

Here is a neat little page that talks about the .410 slug in great detail. I think the dude has a "thing" for them. 410 slugs Where as Chuck Hawks doesn't seem too impressed with the shotgun over all.

I can't really find anything to compare it with since not much shoots a bullet that light that fast. At least not that I can find quickly. I would say maybe like shooting a +P+ .380 out of a carbine? Or maybe a round ball smaller caliber muzzle loader.

Deffinately not as impressive as I first thought.

I originally stated the 45 caliber thing because I remember have seen barrels listed as 410/45 cal.

Sorry about any confusion I may have caused. I am suprised nobody caught it and called me on it.

Paul