45 Colt in a Rifle

One of my spring projects is to work up some loads for a 45 Colt. Specifically, I have a 20" 460 S&W Magnum barrel for my TC Encore and I am after something a little less punishing (Something like a 2600 fps 240 gr bullet out of a 5 lb rifle gives me pause). One thing about this load is that there will be a long jump to the rifling (Something like 0.5 Inches). Any one have an idea of how this jump will effect accuracy? Or does it really matter with this rifle? Data point: The last time I shot this gun with 460's I was getting about 1 inch at 50 yards.

I have some H110 and Lil'Gun and 100 225 gr Flex Tip seconds on hand. I have a box of factory 45 Colt flex tips for reference, but the handloads will be hotter. I also have a bunch of cast bullets to play with. I will load the Flextips with Contender/Blackhawk data and the lead at standard pressure levels (I have a Bisley and a Flat top (new model) that want to go play, too).

While the Rossi is a temptation, I already have a Marlin 1894 in 44 Mag in the safe and I really don't have the room for another lever gun in the collection. And, I already have the Encore and a virgin 6.5x55 barrel that needs to be broken in...

The work just keeps piling up. The problem with being retired is that you never get a day off...

The thing is that I am not sure how safe it would be to load the 460 cases light. The case is 1.8" long and the powder would likely not be evenly distributed. My approach will be to find a heavy load that will work in the Bisley (7.5" barrel) and I will get what I get in the Encore. I have another Bisley in 44 Mag with a 3.5" barrel that is a lot more accurate than I am, so I have hopes for the 45 Colt.