Your SRH is chambered for 454 Casull, isn't it? If so, it's good for up to 50k loads or more. Due to the larger case of a 45 Colt compared to a 45 Win Mag, any Win Mag load in a Colt should give several thousand pounds less pressure than in the Win Mag. I have seen loads with 250 grain bullets at 1400 fps in Ruger 45 Colt chambered revolvers, so your 185s should be pretty sweet at that velocity!