A new model is in progress, and it's not the one pictured above - that never really took off. After a few years I've been reunited with my Lego, so although I'm doing some design in LDraw, it also exists in real life this time. It's a Bushmaster ACR, and so far the lower receiver has been built and I've pretty much finalised the design for the upper receiver, magazine and bolt. Pics coming soon of the model in progress; both photos and LDraw model screenshots.
Suggestions for future models are welcome, but I probably won't act on them, I still have very limited time to spend building. Any feedback is welcome, but I don't do instructions so please don't ask. Maybe when (if) the ACR is finished I'll upload the LDraw model file to Brickshelf. Anyone using LDD instead of LDraw, tough :D