I didn't think you were supposed to use Foster type slugs in a fully rifled barrel. But I don't have any experience with them so it just what I have heard. Would like to know more as I may try to use 12 ga slugs this season.
Its ok to shoot foster slugs in a rifled barrel. Leading is typically only a problem occurring only in the minds of gun and hunting magazine writers........ But the accurracy of foster slugs isn't the best.
The Brenneke slug is not a foster slug. It is an attached wad slug, usually full bore and usually a bit harder than the pure soft lead foster slugs. Brenneke slugs, in my experience, typically shoot much better than foster slugs, and hit harder.
Remington gun, Remington rifled barrel, range 75 yards? How about the Remington Buck Hammer. It's only at a disadvantage at ranges you shouldn't be shooting an iron sighted slug gun at, anyhoo.
Another word of advice. Slug guns are indifiduals. I have sighted in guns of the same brands, same barrels and found accuraccy with different brands of ammo in each gun. buy a box of several brands and try them out.