This is a six barrel testing platform basically with no fansy or polished stuff involved here. The barrel's are chambered for .357 but I have only been using 38 special cartridges so far with any tests. The bolt carrier and rear barrel plate are T 6 aluminum and the bolts are 1/2 inch cold rolled. I used the gears that I had from a D&E build that I stopped working on years ago. The main shaft is 5/8 cold rolled turned down to 1/2 for the gear with a keyway slot milled into it for headspace adjusting. I drilled a 1/8 hole through it and pressed a dowl pin in it to turn the carrier from the rear. The barrel plate is dowl pinned and is attached to the carrier with 2- 1/4 inch bolts.
Some of the tests are using a pin pressed into each carrier groove that protrudes up into each bolt bottom for a positive ejection of the spent cartridges as the bolts move rearward. The bolts have a slot machined into there bottom areas to allow for this. Another test is moving the cam followers closer to the middle of each bolt to shorten up the housing length. The recoil is absorbed by a piece of 3/8 inch thick flat stock that is welded to the box cam from the under side after milling a 3/8 slot in the box cam exactly even with the bolts backside pathway at BDC with a cartridge chambered. The cam path was releaved some at BDC so the cam followers don't take any recoil at all.
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