I sold a Ruger MKII 5 1/2 bull barrel because I was able to shoot my M63 far better.
I completely believe you, though it seems it would be the other way around, especially when talking about a target pistol like the MKII.
With that said, I also have a 5.5" MKII bull barrel, and my example is far from the most accurate .22 I have. superbly reliable, but only mediocre in the accuracy department with bulk ammo.
