If you're talking about Jerry Miculet, I've seen and handled some of his ammo.
It's guess what.............
A home cast 148gr DEWC, looks to be from a Saeco mould;
Uses 2.7gr of Bullseye
Mixed brass, some nickle plated, most lightly tarnished;
(exactly what most PPC shooters have been using for 30+years)
Loaded and fired by the "Bushel Basket-full", through what are essentially out of the box guns. He uses full strength rebound springs to "push" his finger back to get the speed he's capable of.
He probably shoots a heavier load in "sactioned" matches with power minimums, be He said he was using the old "standard" wadcutter load for the speed records- 2.7 of bullseye.
BTW; I witnessed the last round of "Speed" records he shot. He makes it look really easy, too.
But, I can't make my fingers move that fast !!!!!!!!!!!!!!
-And I've only shot an estimated 3 million rds of .38 in the last 30yrs since I shot my first club match at 17yrs old.
GREAT SHOOTING JERRY !!!!!!!!!!