Dynamat
http://www.dynamat.com/products_comp...lity_paks.html is the stuff you can pack around mechboxes to help damp out noise.
As for the .50 it was pretty easy to set it up to hit targets at long rage. You do the math and dial in the T&E knobs, pop off a single round a piece of scrap metal, pull off you ear defender and a couple seconds you'll hear a ting as the round hits down range. Great fun!