I also run BT 250 WFNs out of my M69 over about 10 or 10.5 grains of Unique or a similar load of N350 which I think leaded less? It kills well. Night and day from a 357 bore at the same speeds.
I have not pushed them faster because it's a light gun. Regardless it's about 1050-1075 fps. Shoots nice tight groups at 50 yards and the bullets are still flying straight at 100 yards as well. I'd imagine at 1200 fps they'd be even better.
