I decided since I can't seem to find the time or space to get a costume off the ground, I'll build a (sort of) working 1:1 scale bolter. The internals will strip a round from the magazine, feed it into the chamber, extract and eject, and the gas system will be present. If it was made out of suitable materials it would actually fire, but of course it will be plastic and relatively soft metal because 1) I don't own a machine shop and 2) I don't feel like doing hard time. Here's a list of features off the top of my head:
- Bolter will be made of metal pipe, .090 sheet styrene, and assorted metal components from the hardware store
- Barrel will be roughly .75 caliber, ending flush with the front of the receiver, and muzzle brake will be 2 inch diameter
- Barrel will be rifled - I'll need to calculate an appropriate twist rate - Greenhill formula gives 1:56 for a 1.5-inch long .75 caliber projectile but this may be too slow to actually see the rifling twist within the length of the barrel
- Dummy cartridges will be constructed from once-fired .50 BMG brass cut off just before the neck with a pipe cutter, filled with wax and with an appropriate dummy projectile seated
- Bolt and receiver will be nesting metal pipe with an AR-15 buffer tube spring behind the bolt; extractors will be dual claw-type with a blade-type ejector
- Charging handle will be taken from an airsoft MP-5, G-3, or similar
- Chamber will be a .50 BMG case cut off at both the neck and the base so the dummy rounds nest inside it
- Bolter will operate on the gas-delayed blowback principle; the projection under the barrel will be the forward point of the gas tube and may incorporate an adjustment for humidity/altitude
- Trigger mechanism will probably be from an AR-15 kit unless I can find one from a different rifle for cheaper
- Projection over the barrel will be a laser activated by a pressure-switch on the foregrip, which will be taken from an airsoft Franchi Spas-12
- Sights will be protected fiber optic blade front and protected ghost ring rear
- If I can find a way to do it, I'd like to incorporate a shot counter - my initial idea is a little dial on the rear of the receiver numbered 1-30 that trips down one each time the action cycles, and if I can figure it out I'd like it to reset to 30 if the magazine is removed and a fresh one inserted before it reaches 1
- Magazine release will function
- I'd like to incorporate a bolt-hold-open follower but it's complicated and I may have to wait until the second build, if there is one
This whole project depends on finding a reasonable price for once-fired .50 BMG, but that shouldn't really take more than patience and a google search or trips to a few gun shows. It may not be immediate but I've put a lot of thought into this so watch this space. When I get some concept drawings and initial plans scanned I'll post them.
Comments? Suggestions? Criticisms?
WH40K Pepakura File Library 
