JP and some of the others used lighter and heavier buffers, carriers, springs and such to reduce recoil and muzzle jump to increase speed of the follow up shots. A very specialized and finicky proposition.
What's the load it won't run?
The JP stuff isn't finicky, it runs great as designed, their just isn't any "reserve" for a really dirty gun, it'll get sluggish faster than stock. Match guys know how long they can go without cleaning, and if it wasn't reliable, they wouldn't be entering sponsored money matches with something that they thought would choke.
LC brass, WW primer, 55gr Montana Gold FMJ, 25.5 gr TAC.
