It was designed around 110 gr FMJ. With care, lighter bullets are good too. As for factory .30 carbine, there is more out there than you seem to think. There are, currently, factory FMJ loads from Aguilla, Armscor, Hornady, IWI, Prvi Partizan, Sellier & Bellot & TulAmmo. JSP/JHP loads are available from Federal, Herters (rebadged TulAmmo, I believe), Hornady (FTX), Prvi Partizan, & Speer (Gold Dot). These are what are currently available on Gunbot. Remington & Winchester have loaded both FMJ & JSP in the past. I buy PPU for the JSP & Armscor for plinking and reloading brass. I'd far rather my carbine than yet another AR variant. YMWV.