It doesn't muffle or stop the sound, it directs it forward as opposed to the side.
I'm not looking for an argument; I can tell you this *will* change the total volume of sound, as well as the frequency characteristics, even if slightly.
The ‘report’ of a gun is the sound an observer hears. In this case, a sound pressure meter. When they want to determine if it meets the definition of a silencer, there is no procedure set out in Law, but there are industry standards. The RCMP technician from the SFSS lab. will set up the rifle in a rest and place the meter at a certain location (such as to the right 1 metre away from the muzzle, behind and directly above the head of the shooter; I don't know what they prefer). Take readings from a series of shots with the device and without. If it can be shown to reduce the sound *even a little bit*, it meets the definition. Even if it is completely un-changed for the deer down-range from your blind, that is _absolutely_ not the position where they will place the meter.
(If the cops want to be d!cks, they can wave the sound meter around until they find the one spot that supports their argument the most. YOU have no control over the conditions.)
Is it a device? Does it muffle the report of the firearm? Was it so designed? This is what is called a slam-dunk.
Hey guys! I have hollow tubes that make SVTs quieter for sale! Hang on a minute, someone's knocking at my door…
It is also not an extension, as those are required to be permanently attached, with continuous rifling. Chopping the barrel to remove the brake is not a device, contrivance, apparatus, whatever, all of which mean an external thing applied or used in conjunction with the original thing. (I am talking a serious discussion of the Law here, looking at the way terms have been defined and the stance the Crown has taken previously. I am in total agreement that this *should* be a permitted modification.)