Good question - I don't have all the answers. The range is the Belmont Rifle Range in Brisbane. The new suburb is an extension to Carindale. I don't have details of the test equipment or the testing organisation but it was to the satifaction of the EPA.
There were several test points with the closest being around 500m away from the range boundary. There were several monitors installed in the area for a period of time (a week?), so variable winds and different elevations but otherwise stationary at those points. The range is a public range so everything the public drag down there should've showed up during the testing. 50cal and the various 416 derivatives (416 Cheytac?), and the 338 Lapua are not allowed to be used on this range due to the "danger template" that has been approved for this range.
Our group, Big Game Rifle, has been labelled one of the main offenders for noise, and we have been proven guilty thanks to the testing. Our group shoot once a month and the testing technicians happened to be at site so that we could correlate our bangs with that being measured. We took the opportunity to check the 375 break and break-less, as that had also done with smaller cartidges from the bench (smaller being the 300WM - these are common and often braked in their tactical package). No difference at distance braked or un-braked.
We typically shoot 375H&H, 458WM, 416Rigby, 500NE & 505Gibbs as standard at our shoots, so we made the meters flicker a bit.
I haven't seen the report but have been told by club officials of the findings. Brakes can continue to be used except there are areas on the range where they can't be used but only to limit to noise coming back to the shooters and the main office.
