As ElDiablito said about the Barnes SpitFire T-EZ,
"I’d definitely push them with as much powder as you can handle."
Buddy and I just finished up our WA muzzleloader season with a cow opening morning (Saturday) and a spike bull this last Monday (spike bull only GMU without a special permit). We're both shooting the same setup: CVA Accura 50-cal, 26" barrels, 290 Barnes T-EZ s, with 100 grains of IMR White Hots (2 pellets). Both elk were broadside shots: my cow at 90 yards and his spike bull at 40 yards.
Both bullets opened perfectly at those distances and charges and both bullets were bulging out the hide on the far side. Mass retention looks good, but I haven't weighed them yet. No passthrough and no blood trails.
While both elk died, we were a bit surprised that even the 40 yard shot didn't have an exit wound. An exit wound really helps with depressurization and blood trailing (when necessary), so our first change will be upping to 3 White Hot pellets (150 gr equivalent) and doing some penetration tests. Maybe change bullets, but these are extremely accurate and two elk did die.
@ElDiabloto, as we had similar results (bullets just inside the far side hide), what powder and charge are you using?