If suppressing supersonic, is barrel length significant?

[Bret]

I just got my first rifle suppressor. It's a KGM R556 suppressor that was "free" when I purchased an IWI Carmel. Since it's full auto rated, I want to use it on an upper for my M16. It came with one muzzle device that is used to attach the suppressor. So, I can only use it on one upper until I buy another muzzle device. I typically like to shoot a 14.5" M4 upper but can use a shorter upper if the sound suppression is significantly better. All else being equal, is there a noticeable difference in sound suppression between a 14.5" barrel and a 11.5" barrel when the bullet is supersonic?

[georgeib]

Having tested the same suppressor on a 16" and an 11.5", I can tell you that there is a noticeable difference. Though the 11.5" is definitely louder, it isn't annoyingly so.

I will add that the longer I shoot suppressed, the less tolerance I have for shooting unsuppressed. Any unsuppressed centerfire rifle is just obnoxious in comparison, regardless of barrel length.

[Bret]

That's interesting. I made the assumption that the higher the velocity, the louder it would be. I neglected to account for the generality of shorter barrel rifles being louder. I use the 14.5" M4 barrel. Thanks.

[georgeib]

That's interesting. I made the assumption that the higher the velocity, the louder it would be. I neglected to account for the generality of shorter barrel rifles being louder. I use the 14.5" M4 barrel. Thanks.

You got it.

[MegademiC]

That's interesting. I made the assumption that the higher the velocity, the louder it would be. I neglected to account for the generality of shorter barrel rifles being louder. I use the 14.5" M4 barrel. Thanks.

The bullet noise change is negligible compared to other variables that influence blowback from a shooters perspective, with gas guns.