Gamebore manufacture a very good steel load called Pro -Steel.Excellant plastic shot cup, I have been told that it is possible to shoot them through IM & F chokes, but I err on caution myself.Should be good to shoot through M or less.
I have shot them and they seemed very good, broke clays very well, out to 40 yards.The ones I used were 7/8oz load size 7 1/2 speed was advertised at 1375fps.Initial impression was very good.
Now if only I could get over my prejudice.