JB is either 1000 or 1200 grit, basically valve lapping compound. Haven't seen JB since 1982 when I toiled for FW Woolworth in the sporting goods department for almost a decade. We sold insane amounts of guns and ammo, also did minor gunsmithing such as bore and scope sighting, stock and barrel finishing, and cleanings. My wife used to comment of me smelling of Hoppe's #9 from time to time. Most interesting job I ever had was with "Woolies". Miss that place to this day.Would you know about what grit J-B bore paste is in comparison? I’ve used it a couple times. On the USR, and maybe one other of mine. Brother in law introduced me to it when taking me shooting years ago during cleanings after. Thanks kindly.