All barrels marked 6Mm will have the faster twist, as far as I have found all 6MM sporters have 22 in barrels, every rem 244 ( 5 or 6 ) had 26 in barrels, I worked up a load for a fella that had one that would shoot 100 gr rem corelock and sierra flatbase under 1 inch for five shoots but not not much else, I had a rem barrel marked 244 that had a 1-10 twist, I attended several shot shows a Remington rep couldn't answer any questions I had about that, however he gave me a contact to some that could and he confirmed that they changed to 1-10 when the 243 was was labeled the new daring in town and was the superior of the 2. As for the performance of the two in the real world if you kill it with one you will kill it with the other, the same applies to wounding, I frequently hunt predators during deer season, my favorite rifle for varmint calling is a kimber in 17 Rem, I tagged 2 deer and a black bear using this rifle while doing so, the black bear got ugly, I countered any further unpleasantness by going to a sako sportier in 6MM PPC, I use a ( no longer made ) 75 gr Nosler solid base, I've hung a tag on a additional 5 blacktails and another black bear, while not a ideal big game bullet, it has performed better than I could ever hope for, it is a far better choice than the 25 gr bullets of the 17 rem