I originally had my brace equipped 7.75 inch pistol with the carbine handguard sighted in using Speers 147gr FMJ. The firearm was taken as a backup to my HK MP5 for a PCC/Subgun class. I settled on that ammo because I primarily shot the MP5 suppressed and I only wanted to have to take one type of ammo. My Scorpion ran and shot beautifully with that ammo. Interesting note, with the 147gr ammo zero'd at 25yds it was back dead on at 100yds.