Why not more SBR in PCC? in Pistol Caliber Carbine Posted June 13, 2019 My last Efile Form 1 took 16 business days! The SBR I did on paper took over 8 months. I built a 8” on a QC10 and in March finished an MP5A3 clone with 8.6” barrel. The Mp5 shoots much softer and is easier to control but trigger travel is longer and harder to shoot fast splits on in your face targets.