TargetTalk

I know several shooter with SP's and they all resize there ammo(cci eley sport aguila). most of the problem with the ammo is extra wax one the bullet which stops the bullet to be fully seated in the chamber.

I have a similar problem with my old SPE. If the barrel's chamber face gets a good film of cartridge lube, gun oil, and powder grime on it, and especially if the cartridge I'm using is a tight fit in the chamber, the bolt won't seat the rim right up against the barrel face. Consequently, a good portion of the firing pin's energy gets expended seating the round. It's only a few thou', but it's enough to guarantee plenty of light-strike misfires.

Problem eventually solved by a combination of wiping the chamber face clean every few hundred rounds at most, and sticking with cartridges that aren't excessively lubed.

a fellow shooter has a habit of cleaning the chamber with an angle bore brush after each mag durring timed and rapid strings. I asked him why he thought he needed to do this and his explanation was lube. I have gotten in this habit as well (not every mag)
shooting cci.,(most reliable in my sp) ely sport and aguila both gave me light strikes