Well I don't think 60,000 is reasonable in either case. And 'speculate' was a good word to describe the estimate. Then again, predictive software models aren't always 100% accurate at the extremes. But I think that Quickload is probably much closer to the truth.
Even with the longer OAL provided by the second cannelure, I'd have worked that up, very carefully, maybe in a Redhawk, if I was to do that at all. Probably get 1100-1200fps with a typical revolver.
Please note that upon reviewing my Quickload input, somehow the first time through I put 10.0 grains of Unique, instead of 10.6. The pressures go up a significant amount with that extra .6 grains of powder and I have edited the first post.
This would imply that the load is quite sensitive to case capacity, so it is possible the pressures could vary a fair amount depending on the brass used. Then again, Quickload also has a standard disclaimer that it doesn't always get the correct numbers with straight-walled cases and especially in revolvers. Usually, you have to adjust the case capacity upwards (up to 10%) to match the actual muzzle velocities, or fiddle with the burn rate numbers. But that would mean real-world pressures are probably lower than what is first predicted. Bumping the case capacity 10% or so drops the max pressures to around 35,000-37,000PSI, so the truth is probably somewhere in between. If we think about a revolver having freebore (due to the cylinder throats) this makes sense.
It's a hot load for sure and I really don't see the point of trying to do that with Unique. Trouble brewing, I'd say. Throw in the usual disclaimer that powder burn rates vary per lot, etc., and there's even more confusion. Bottom line: That heavy of a bullet with that fast of a powder is going to be a very touchy combination at the top end.