Gemtech has Blast Jacket, a muzzle blast redirector. All muzzle blasts are forwarded to the front.
http://www.gem-tech.com/store/pc/viewPrd.asp?idproduct=1106
Price: $195
http://www.youtube.com/watch?v=hY0Jfc_TCgA
Here' the video from the field test
http://www.youtube.com/watch?v=00-lTkGhL9s
From: Gemtech