My 15" Encore in 460 was the most brutal thing I ever pulled the trigger on. On the third round I was unable to hold the gun steady enough to hit a 20 ounce bottle at 20 yards. I damaged the cartilage in my wrist after a few more rounds and had to stop shooting all but the mildest handguns for better than 6 months.
A muzzle brake made it a controllable barrel. After I had Bellm cut his brake into my barrel I was able to chrony the factory Hornady 200 gr rounds at 2800 fps. That's faster than you should push a 200 gr pill out of a 30-06 and you're holding that thing in your hands. I later played around with 230 gr ball over 2500 fps.
As I continued reloading I noticed that I was gradually backing that thing down. I never found reduced loads that used safe published data, were comfortable to shoot, and didn't involve Trail Boss slinging 250 RNFP at 1300 fps. The case is so big (more case capacity than a 308 and a higher pressure) that you're going to have a hard time loading down to moderate levels. 5744 kinda worked but it would leave unburned powder in the bore.
If he's a reloader I'd get him a dedicated 45 Colt barrel (NOT a 45/410) and he'll have a ball. Trail Boss plinking loads will run 800 fps and he can work his way up to JHPs at 1600+ fps. Everything in between is easily assembled with a Colt. H110 will limit you to higher speeds but you can step down a bit with 4227, 2400, Power Pistol, and tons of other powders.
A 250 gr flat pointed hunk of lead at 1200 fps will drive stem to stern through any deer.