My dad and I were trying to come up with a subsonic loading for my MP5 in case the gentleman that had the suppressor is there this time. Last time all I had was supersonic ammo. I bought some XTP 147gr bullets from sportsmans warehouse. My dad is currently using bullseye powder. We've gone all the way down to 3.2gr and in my MP5 it's still going supersonic. Anyone know of a loading or how low we have to go to get this stuff slowed down? This is in a factory German MP5 8.85 inch barrel.