We've had several threads about the 45 Colt in Ruger only loads, but a recent article in the new Handloader (October 2014, #292) really surprised me.
According to Brian Pearce, the Redhawk is capable of far higher pressures than I was aware of.
He lists loads that "approach 50,000 PSI". Some of these include 26.5 H110 under a 335 WLN for 1500 fps, 23 gr of Enforcer under a 360 WNFP for 1450 fps, and 22.5 H110 under a 400 gr WLN for 1300 fps.
I personally found my best load to be 21.0 Lil Gun under my Lee 300 RF (drops 315 gr actual) for 1230 fps from my 4" RH. This stays in the range of 32,000 PSI. I backed off to this load from 23.0 gr, mainly due to shooting comfort, but since EKC graciously gave me some new grips, I feel better about trying some warmer loads in the future. Of course, I have only about a 1/10 lb of LilGun left, and no powder on the shelves for a couple years now.
I don't feel under gunned with 315 gr going 1230 fps from my RH, and 1600 fps from my R92 16", but dang, if Mr. Pearce is correct, there's a lot of power left on the table.