question on 300 whisper barrel length

[crowminator]

Hello, I ordered a barrel from Pacnor 30 cal, heavy varmint, 1-6.5 twist. Itshould be ready to ship in about 4-5 weeks. Has anyone had any experience with a twist rate faster than the usual 1-8 twist. The blank I ordered will finish up to 26" length. Has anyone had any experiencce with the barrel longer than 16" I was thinking the longer barrel would be quieter with a suppresor because it would take less powder to get up to the speed of sound.