Tell you what.
I'll run the W231/45Colt/HNDY250 load tomorrow
5.5 Ruger
Oehler Chrono
(Today's load for me is Lyman's 452454 over 9 grains of Unique -- so I'm no stranger to Unique. But the OP has W231)
For record, however, many of us have been running
Quickload for many, many years, and have come to both calibrate what it can -- and cannot do.
Case in point: I got my 458Win back from the gunsmith last week. Yesterday I asked QuickLoad to give me a fun 'sweetheart' load with one of my heavy cast 45 rifle bullets I run in a 45-70 and a 45-90 (Lyman 457132/Postell/535gr) -- and to do it w/ #2 alloy weight which happens to be 505gr. I also told it to give me max case fill for ~12,000psi, 1,200fps, and max burn completion -- and adjust pressures/velocity for an OAL of 3.22".
Racking & stacking the long list it gave me I chose IMR4198/28.0gr.
In the end the assembled cartridge info in my Range Log looked like this:
Ruger/M77/458Win Loaded 9/13/13
Lyman 457132_Postell #2 (505gractual/IMR4198 /28.0 /WinCase(95.0H2O)/FedLrgPstl
QL= 11,597psi/1,170fps(24")/Lym450Sized/Lubed:0.459"/OAL=3.22"/HvyCrmp_LstGrsGrv
Actual velocity over five rounds this morning at the Range?
1,194fps ± 09
But REALGUN is absolutely correct. The 45Colt/W231/HNDY250XTP/900fps load suggested above is not in the books.
So in keeping with caution: "your mileage may vary"
(which is also why I said "Ruger Only" and put expected pressure in
red.)