The chore boy works great as I have tried it. Cleans it quick.
Note - I take bore paste to all my guns when I first get them, used or not, and give it a good scrubbing. It knocks all the high spots off and smooths out the bore nicely making all my guns a breeze to clean after that. I did this with my 45 that I fouled the holy heck out of. It took about an hour of elbow grease to get all the grime out. The bore was notably more shiny and I found that i can remove metal forever with this stuff, so just go until your fouling is gone because you'll never get a clean patch doing it.
Now I can shoot 500 rounds through that gun and it only takes a bronze brush and a little elbow grease to sweep the grime away. I have never noticed any accuracy change either in the negative direction. Actually, the opposite, if anything, my rifles I've done this too are more consistent once fouled with a round or two.