TXHUNTER58,
I have had the same trouble with BM3 and the No Excuses 460. Huge groups compared to 777 2F. With 777 I get around 1.5" to 2" groups at 100 yards using 90 grains. With BM3 I did good to get 2" groups at 25 yards. I feel it works better with lighter bullets as the 250gr Shockwaves shot very similar to the my 777 load with BM3.

As far as the PB's shooting better it could be the plastic cup is doing abetter job of sealing the bore than a conical. Maybe they are not obturating quick enough or something like that.