Here's something billed as a "working" Lee Enfield sniper rifle ... made of Lego blocks. While it's not exactly equipped for wetwork in Afghanistan, your kubrock figures might have reason to lose sleep. From the website:
This rifle has a sniper scope, bi-pod stand and 2 8-round magazines. The stand is collapsible and detachable and clips onto the front of the barrel. When it collapses the legs are parallel with the barrel.
The sniper scope looks authentic, but when you aim with it you actually look through a small hole underneath the scope, as I couldn't make the actual scope hollow.
Video below of the rifle in action: