Saw this discussion while researching for a good reduced cast load for bear SD. It's been 1 1/2 years since the post but with Covid thought you may still be working on this so here's what I've found in loading for the 454.
I'm loading for Cast Performance 360 WLN. When crimped in the groove 100% density for H110 is abount 26 grains.
Load is for Freedom Arms M83 which has a slow 24" twist rate and it may not stabilize bullets heavier than 360.
The only data for heavy cast I've found is Hodgdon and their max load is 24 grains which is where I started out as it's 92% load density and I don't want to go lower and increase chances of a squib load. Tried 25 grains for 96% load density and it made a noticable increase in recoil. My previously loads have all been upper end jacketed loads with H110 Rem 7 1/2 primers and FA brass. Using Hornady 45LC dies and a Redding profile crimp die I've never had any squib load (don't recall shooting in winter though.
454 dies are recommended because they size the cases smaller to (in conjunction with a heavy crimp) keep the bullets from moving during recoil and makes for more consistent ignition. The Lee factory crimp dies are apparently an alternative to the profile crimp die so with either one you'll be seating and crimping in 2 steps. The Remington primers are what the Freedom Arms load data uses. The original Freedom Arms brass had large pistol primers and some reloaders have cut down 460 brass to 454 length and reported better results with H110 and large pistol than using the small rifle magnum primers.
I'm sure you've found in your research that the heavy cast don't need to go over 1300fps to be effective and going faster may be counter productive.
So H110 is faster than I want and so it kicks more and is going to make shot recovery slower, it also is high flash.
I want low flash so when I'm camping in a tent I won't be blinded from a shot at night.
In my research I've determined N110 is the powder that meets all my requirements. Low flash, can be downloaded, provides the velocity and has the side benefit of being clean. No load data for heavy cast but I've extrapolated that 18 grains would be a safe starting load and would be about 88% load density with 20.5 grains being 100% with that 360 grain bullet.
Of course the shelves are bare at the sporting goods store so I'm having to use what I have on hand. Blue Dot is the right burn rate for the velocity but high flash. 2400 can be reduced but is also high flash. #9 has had the same problem with squib loads from reduced charges. IMR or H4227 can be reduced is lower flash so it's what I'm going to try, although it's not the cleanest.
Herco, Unique, CFE Pistol, and others may work for 1100 fps or so. I'm aiming for 1300fps.
Load data for this cartridge does have inconsistencies from source to source and some is just bad. The lower charges of H110/WW296 should be done away with. I've seen high pressure loads with bullets that aren't designed for it and that can wear and or crack the forcing cone. Also Lil Gun has been attributed to forcing cone wear and gas cutting of the top strap on revolvers. That's all I've got, hope some of this is useful.
