I use a cast Lee 165gr TC bullet, exclusively, and the great majority of my competition is Steel Challenge. Though the rules don't require Major, or even Minor, power levels I keep it loaded up a bit because a few times it came down to the speed of the "stopper popper" falling to declare a winner. It only has to happen once to be worth it. I see it happen at least three time a day, and our shoots are two-day events.Sometimes, I am one of the involved!!!
My favorite load is 5.6gr Green Dot in Federal cases, with Winchester WSP primers, loaded to 1.20" with bullets cast from Lyman #2 alloy sized to .401" and lubed with White Label BAC.
The velocity is 1050fps measured at 7 1/2'(5' spread and 5' first screen) through an Oehler M33 chronograph.
I have played with .403" bullets from time to time, but I am not able to load that long, as it touches the rifling too soon. The longest I can go with the .403s is 1.17". I have also loaded some at .406" for 1.14"OAL.
Right now, The .403s and .406s are pan-lubed, so it's hard to get enough lubed to compete with. I prefer to use my RCBS lubrisizer for large amounts of bullets. The pan is just a little messy with lots of bullets.
My gun is a Limited with the polygonal rifling. I use 10mm magazines mostly with a couple K40s that have had their "rail" removed.
As I have the chronograph, I've tried other combinations, ie OALs from 1.09 through 1.20, with almost any powder you can name. Any you name that I haven't tried is on the list, lol.
I've also tried more than a few primers, so that I'll know what will happen should I run out and need to substitute. Tula, Fiocci, Federal, RP and CCI have all been there.
If nothing else, these experiments give me a lot of trigger time, lol.
Have fun,
Gene