I saw an article in a shooting magazine benchtesting some new rifle but that's not important.  In the article it showed a picture of the authors benchrest which included a covered chrony and a pair of fifty gallon barrels welded end to end and used as some kind of suppressor or muffler.  It looked like the end of the rifle barrel was inside the end of this contraption.  Does anyone know how this device works and how I can build one?  

Baffles & chambers in the drums coupled with some sort of materiel that acts as a sponge for sound is probably what they had. No clue as to how well it would work. Based on standard acqustics (sp?), something like old blankets or moving quilts might help.

Wonder if those drums were screw-on?  

I intended to make one of these. You can fill the barrels with tires that are the right size, and it supposedly works well. I have also heard of just bolting a bunch of tires together in an angle iron frame.I want to build one in consideration of my neighbors, and anyone else that might be around the house, even though I have 30 acres outside the city limits. My 100 yard range is about 60 yards from my back door.