There was a thread on chopping barrel of 270 cal

[rimubay]

I'm easily getting 2900fps out of a suppressed 19 inch barrel, 130g Accubonds and a reasonably mild load of 2209 (under ADI book max). I put some Norma factory 130s over the chrono the other day and they were doing 3030fps! NZ Hunter apparently getting 2950fps from an 18 inch barrel with 145g ELDX and Superformance.