Also, I am quite sure that Ryu pointed out it was a little unfair, but that Kanon and Shannon didn't have to wear their own clothes to act as themselves.
Also also:
https://www.youtube.com/watch?v=257Hw7TsykI
apparently the bolt actions are quieter, and it is ammo dependent. Listening to this (model winchester, real ammunition, skip the long start bit) they aren't THAT loud at all. Then again, that one has a barrel, which helps.