Concept pic for a Boltgun.
*** UPDATE*** Actually got off my ass and did it. Current Page. Real pic at the bottom of the page. **UPDATE**
For the same reasons I was looking at a Stormbolter Conversion, I've been tinkering around with the idea of a Boltgun conversion. And I have this G36C just sitting here...
I'm actually most of the way through this now, soon as I get hold of a dremel to chop the second rail, and make up and spray some side panels, I'm good to go.
Oh, and find a way of attaching the etched brass Eagle I got from Games Workshop...
I should probably point out that I'm going for a usable rifle, rather than a fan-boy accurate copy, so I'm probably going to keep the stock. This also means i can ignore the scale (Boltguns are roughly the same size as an adult torso...).

Parts list.
G36C
Couple strips of plasticard.
An extra G36C top rail to extend the current one with.
A flat-top conversion kit to hide the hole from the redundant front sight.
Four extra-long bolts to replace the G36C top-rail ones.
M16 magwell conversion and some M16 mags (got a bunch of mags gathering dust from my old rifle).
Tubing to cut down for oversize barrel.