Ironhand,
This is making me start to wonder about something. Are you sure you really want the bullets to drop in easily?
I mean, ease of loading is one thing, but to me one of the problems with carrying a bullet loaded rifle is the tendency for the bullet to walk off the charge, thus creating an air gap between the powder and projectile. Thus necessitating the need to continually keep checking on the placement of the bullet. With a double rifle, the problem is doubled. Also, keep in mind that with a double rifle, the recoil from the first charge can move the projectile in the other barrel. Which is what I like about a PRB in a double. It stays put where it placed. When I had my 8 bore double, if recoil was going to displace the second charge, it would have on that old girl. 300 grains of Fg does make for a noticable recoil. But everytime I checked, it was still tight.
If it was me, I'd go with the PRB. It's plenty big for deer and such.
On the other hand, if you are stuck with the idea of using a minnie type projectile, you probably should take Fletcher up on his offer. Sometimes, with guns that cannot easily be regulated, one has to use different projectiles in each barrel in order to get it to regulate. It's a real PITA at times. Have fun and keep us informed with the progress.
John