My 300 BO broke so I don't have any info on heavy subs....
But my 762x39 bolt gun works fine.
"Normal" load being a 125gr TNT at 2300fps-ish, sub load being a 85gr .312" XTP at 1000fps
(speer makes .308 and .309 diameter 90gr bullets, or you can play with cast lead, but little light bullet subs are giggle inducing even if you don't have a can. can cause feeding issues though 'cause they are short-n-stubby)
Sub load hit 9" low at 50 yards compared to the super....
But.... there are a few ways to make it all work.
Assuming you have a scope that tracks well, has sufficient adjustment, and does a great job on the box test, all you need to do is spend some range time and build a dope sheet, with a reference at reasonable divisions on how much needs to change to re-zero between the loads.
Or in the finest enabler tradition of internet forums - have a "subs" gun and a "supers" gun.