I tried some D+J hardcast (.410") in my FG with disappointing results but they shot great out of a Ruger Redhawk. My FG is bored closer to .411 and I'd bet yours is too. Have you slugged it? Those .412 pb slugs should work out OK once you find a powder and charge they like. I think the complaints about micro-groove barrels not shooting lead bullets well are unfounded. What lube are you using? I just tried some 225 grain LBT cast bullets with Bluedot that left the first 2" in front of the chamber of the FG leaded. Velocity was only in the mid 1400s. Groups were in the 3" range at 50 yards. I'm quessing that the fast burning Bluedot is too abrupt in starting those slugs down the barrel and thus the leading in that area. With a mediocre load of Lil'gun, that same bullet leaves the barrel at close to 1700 fps and no leading. Might be worth trying a slower powder with cast bullets in your FG. Keep those test results coming!