Odd location for blow back?

[ex95B10]

I recently installed a surefire light tan in color. When I went out to the range today I discovered that there seemed to be gunpowder residue on the left side of the light.
I can not figure out where it's coming from since the muzzle is about six inches ahead.

http://img.tapatalk.com/d/14/02/23/ba9ugyqu.jpg

http://img.tapatalk.com/d/14/02/23/epara3ab.jpg

[Cagemonkey]

A little blow by out of the gas tube retaining pin hole. No biggie.

[ex95B10]

A little blow by out of the gas tube retaining pin hole. No biggie.

Thanks, I guess I just never noticed it before until I got this tan colored light.