Ive used JB on most of mine but i use MX bore conditioner on all of them. My 52cal's bore was so nice i felt there was no need and surprisingly the Savage also didnt need it.
The MX bore conditioner does appear to work as advertised after a few applications. Im not sure if it was the range time on the new barrels or the conditioner but im happy with the results.
My favorite part is sometimes i forget to dry swab before shooting. Using the conditioner vs Remoil i dont get any gummy residue. Remoil is horrible if not removed from the bore prior to firing even with BH209. Using T7 it is unbearable if not cleaned out first. MX conditioner actually seems to help reduce hard T7 fouling but i still need to do more testing with T7 again. Ive only tested it in my old Thunderhawk that had years of use before trying it. It will shoot at least 4-5 shots and no spitpatch is needed between shots.
It does go a long way also. I have quite a few guns and i still have over 1/2 a bottle after using it for almost a year. In my Knights i also use it in the breach area. Primer soot wipes clean with ease now but they shoot very clean anyway.