I got a Browning 1885 bpcs (black powder cartridge) a while back and I need a good load for accuracy. The gun has a heavy 1 in 20 twist barrel, I have used a 526 grain lead cast and also a 390 grain lead cast, both with different smokeless powders and charges with not great results. The best groups I have achieved have been with a Remington 405 grain factory load, any ideas would be appreciated.

If it's a BPC rifle, would suggest you load some actual BP cartridges and see how they work.

I have had one of these for several years and it is very accurate with BP. I would suggest one of the books by Mike Venturino and Steve Garbe for loading procedures. Have tried 9 different moulds, including paper patched, with varying degrees of success. The most accurate has always been the Lyman 459124 a copy of the standard Gov't 500gr roundnose. The front section that rides on the bore fits Badger barrels well. I can hold 6"-7" groups at 300 yards for 50 shots. With black powder you will find that the lube is very important. Alltogether one of the most fun rifles I own.