Hi, C.R.Sam
The Ruger SuperRedhawk is one very strong gun, especially the 454 in Carpenter 465-series steel.
So I must assume use of 45 Colt cases in the 454 chambering, oui?
Okay, use Starline cases.
Finish with a heavy crimp using a Redding Profile Crimp die.
The 250g XTP-HP is listed by Hornady as a "800-1600fps" bullet; good.
Suggest Federal or CCI primers, whether Magnum or not.
So now we got all the stuff we need, right (chrono? safety glasses? luck?)
Powder...........Hornady thinks a WLP and around 15g of either AA9 (14.8) or 2400 (14.9) will get you about 1050fps; Hercules liked about 11.0g Unique; Vihtavuori says 10.9g N350 will get you there, or maybe some N340 to get you close.
Safe-pressure data includes: around 13-14.0g Blue Dot, 19ish of N110, 10-11ish Power Pistol, 12-13g 3N37, 14.0g HS6, 10.5g Universal Clays (from my notes -- "250g XTP-HP, Fed 150, 10.5g UC, new W-W case, OAL 1.587", 5.5" barrel gave 1016fps, ES = 34.4, SD = 14.6"), etc...........
Me? I'd skip that lightweight 250 and use AT LEAST a 300g slug no matter WHAT I was targeting (I like the 300g XTP; I love the 325g Swift; I prefer lead) over some N110, IF I wanted a 1000fps-type load.
Whatcha trying to do?