Optimal Length for 300 BLK

[MMH]

I will be cutting down my 16” barrel on my 300BLK Sig MPX and permanently installing a shroud to keep the ‘barrel length’ over 16 inches. I will be shooing mostly suppressed & mostly supersonic. I will however shoot some supersonic, where I will want maximum energy/velocity. I know that a 9” barrel is very common, is this the optimal size? What would a 11” barrel gain shooting maximum 150gr. Bullets?

[fishman]

Longer barrels are quieter. Also, I highly recommend making your gun an SBR instead of don't the shroud. The cost of the shroud will have paid for your sbr stamp.