This just proves that I should not type load information when I'm not at home where my load computer isMark, tell me this is a typo??
A 255gr LSWC in a 45ACP case out of a 2-3/4" bbl at 1200fps?
45 Super brass is no longer than 45ACP & has slightly less case capacity. That bullet takes up about half of the case capacity, or more, of a 45ACP case (27.3gr/H²O).
I can't concoct a bullet/powder combo in QuickLoad that will reach 1200fps without astronomical pressures, far exceeding what the thin chambers of a S&W 45 cylinder are designed for & in that length barrel.
That would seem like a pretty hot load even in the bigger 45 Colt case in a S&W 625 & its longer barrel.
I try to limit my 45ACP revolvers to 45 Super level loads (~28K psi), even in my 25.6% larger 45WSM case's loads I developed for my 325TR
.
That is my 45 long colt load not my 45 SUPER load