The 275gr has been my favorite so far. I like that weight bullet because it has a better BC than 250gr, doesn't loose that much velocity over a 250gr, and not as much recoil as a 300gr. 44gr SR-4759 and a short black MMP/HPH-12 will just about shoot into one hole at 100yds out of several different 10ML-IIs. JJ uses the same bullet but 5744. I personally know of a LOT of whitetail/hogs than have been shot with the 275gr and I would recommend it without hesitation. Of course both of my ULAs and my blue/synthetic 10ML-II are set up with the 275gr Parker and 44gr SR-4759.
Craig, one of Tom's friends from Ohio, showed up with a NIB 10ML-II at the hog hunt earlier this year. We put mounts, bases, a Burris FF-II(2-7X35 I think) on the muzzleloader just before dark. Using 42gr SR-4759 and a 250gr Ballistic Extreme/MMP short black sabot(what the bullet comes with) had the rifle sighted in ready to hunt in 3 shots! Craig went on to shoot a BIG hog with that load and it did a GREAT job. I don't think his shot was more than 10yds and the hog certainly didn't go 10 feet after being shot. In saying THIS..after seeing what a great job that bullet did on Craigs hog and how good it shot in his 10ML-II, I am probably going to set up at least one rig with the 250gr Ballistic Extreme.