Doing this for fun when I get the time. I spent an hour today modeling the base frame as well as the bolts.
I've been using lots of smooth groups and hard/soft edge stuff lately to quickly subd things. You can download the bolts obj with both just the cage+smooth groups and the post turbosmooth+obeysmoothgroups (add a turbosmooth on the bottom ones) here:
http://dl.dropbox.com/u/1725586/challenge4/bolts.obj

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I'm starting to get used to modeling more things into the main mesh, rather than floating. It's surprisingly easy. I also modeled in the front bits that are on the bottom of the frame to the best refs that I could find. I must have spent an hour alone trying to find photos of that area without the bipod. This is the best I could do.
Here's my max file, 2009 format: http://dl.dropbox.com/u/1725586/challenge4/2/frame2.max
No one stops you