FWIW, I have both the 22/45 and the Mark II target, both with 5.5" bull barrels. I like them both, but if I had to pick one, it would be the Mark II. It feels substantially heavier built in hand, which is subjective, I know. They both shoot fine for me. I don't strip and clean the .22's every time I shoot, more like when they need it. I will use a pull thru on the bores when I am done shooting. No need to disassemble for that.
tom