I'm about to. Still waiting on a barrel. Was planning on working up something subsonic. Hard to find a lot of heavy-for-caliber projectiles though. Settled on 425gn Maker REX. Should be pretty easy to load for. Straight wall, not really precision oriented. If it seats, it yeets!
It is the equivalent of loading the .45acp only a longer version.
The case is slightly tapered and it headspaces on case mouth. For that reason a Tapered Crimp is recommended over a Roll Crimp.
Like with many slightly tapered straight walled cases a more precise bullet seating alignment is needed. A bullet that is canted more will seat the same way often leaving a ring or bulge on the side to which it cants. I have found that the differences in specs of cartridge brass and a .451 or .452 dia bullet will also leave an ever so slight ring around the brass where the base of the bullet is seated. Unless extremely noticeable and if they do not "plunk" when dropped into the chamber, they have all fed, fired and grouped as well as others.
I use a Hornady 4 Die set which includes Sizer/Decapper, Flaring, Seating, and Taper Crimp dies. Since the cartridge headspaces on the mouth which touches a slight ring edge inside the chamber too much crimp will case the cartridge to go past that ring and into the barrel instead of resting on the headspace ring. When crimped properly a round dropped into the chamber will make an audible thunk or plunk sound. It is the mouth hitting and stopping on that ring. When tilted back the cartridge will drop out freely. When that is achieved you know that the die is set up properly. I have mine set to .474 dia and it works well for both rifles.
For 225gr to 260gr bullets LilGun has worked fine for me in 2 different rifles. Each will shoot 1" to 1-1/4" 3 shot groups with various bullets in that weight range. I briefly toyed with some 300gr DeepCurl bullets with LilGun and groups opened up to 3"-4". A change of powder may be needed but I never went beyond that initial testing.
.450bushmaster.net is a pretty good site to get a wide range of information.
Here is a link about the case bulge issue I experienced through having a friend seating his bullets.
Taking the extra time to eyeball the bullet as straight as possible has taken care of it.
But once a case had that bulge there was no way to get the bulge gone internally unless it was able to be chambered and fired.
At 50 yards .5-.75 inch 4 shot group. At a hundred right at or just over MOA. Running a 1.5-5 leupold german reticle on a Ruger ranch rifle. Which does what I need it to. Smallest thing I’ve shot with it was a Gatorade bottle. But that’s back when it was cheaper to shoot medium to large bores.
I had good results hunting with the factory Hornady black 250 gr load so I duplicated it with the same 250FTX bullet and a max load of H110. Same POI, velocity, and clover leaf group as factory. Critters cant tell the difference either. They hit the ground like a full feed sack that slid off your shoulder.
Make sure you check the brass length after firing and trim to length. 450 headspaces on the mouth of the case so it is critical. Also do not roll crimp the 450 for the same reason. I use a lee factory crimp die.