It will be louder to your neighbors on the range, not to yourself. Also, some outfitters don't like their guests to use them. That said, the difference it makes on an overbore cartridge like the 300 RUM is huge, lots of gases to redirect. Mine shoots like a 223 with and a 30-06 without (20 lbs scoped weight help). So, if you go hunting with it alone, by all means put one on.
F 135 - the right choice