I have had similar problems with the BM3 and heavier bullets but not that bad with lighter bullets. I plan on doing some more testing after the hunting season.

Try the 250's with the 777, they work well for me with 100gr of powder, under 2.5" at 200 yards and in my gun they load almost as easy as a powerbelt.All though mybore may be more broke in than yours after several hundred shots through it. I don't have to swab until the 6th or 7th shot most of the time and can still group under an inch at 100 yards.

Glad to hear you have found a solution, good luck.