It's 5.7 but CHEAPER.
This review of the Palmetto State Armory Rock pistol in 5.7x28mm highlights its affordability compared to the FN Herstal variant. Initial range sessions encountered malfunctions, potentially due to a heavy aftermarket optic and lightweight frangible ammunition. Reliability improved significantly after switching to Federal 40-grain 5.7x28mm ammunition and removing the optic, suggesting a combination of ammunition and slide weight sensitivity.













