There are others here with a lot more experience with these barrels than I have and I am sure they will chime in. I have loaded only lead shot. I'd be interested in learning of anyone's experience with Hevi Shot. I haven't shot many .45 Colt rounds out of this barrel but if I recall correctly, I was able to get 3" groups at 50 yards. The long jump that the .45 bullet has to make before engaging the rifling results in less than impressive accuracy. The sights are also a little on the crude side so I don't think that helped. You can get some .444 Marlin or 9.3X74R brass and load up some ".450 Mongo" loads for this barrel. Those who have done so report getting good accuracy. The longer brass eliminates the jump the bullet has to make. I did buy some pricey 9.3X74R brass but haven't loaded any yet. Google .450 Mongo for load details. Yep, mine has fixed sights too. BTW, if you get a new barrel, I think you can also get it in 12". As for me, I like the Super 14 length. Hope this info helps.
Mike