The first version worked very well and I was happy with it when I tested it at Millcreek Park in January.
However, since it relied upon glue to hold the locking tab in place I had problems with it breaking off. Also, the thin PETG was not sturdy enough and broke as soon as I tried to barrel tap someone.
The Rev.2 slide breech was made out of pure overkill with an emphasis on modularity. This design basically acts as a very long pipe coupler and therefore allows you to switch out the barrel piece by simply removing the screw that acts as the locking tab.
It is sort of difficult to machine though since the inside has to be bored out to a precise tolerance. In hindsight this one could have been made much more easily out of 3/4 SCH40 pipe.
Mechanical Drawing: http://www.captainsl...ide-breech2.gif
The Rev.3 slide breech was made to reduce weight and complexity. Discovering that I can actually use a 1/2" ID barrel effectively with my foam it made it very easy to find thickwall polyester tube. This negated the need to have the part compatible with 1/2 pipe and therefore the machining was a bit easier.
Mechanical Drawing: http://www.captainsl...ide-breech3.gif
The Rev.3 design could be made out of 1/2 SCH40 PVC, but I had 1" OD black delrin on hand and couldn't resist making it out of that because it's such a nice material to machine.
1. I used the lathe to drill the ID to 5/8", then used a needle file to widen and soften the front half of the inside. This allows the breech to slide open easily.
2. I lathed down the OD of the rear 3/4" of the piece so that its OD is 0.84" (to make it compatible with pipe fittings)
3. I used the knee mill to cut the opening and add the notch for the locking tab
4. I cut a 3/4" length insert of polyester tubing to nest in the rear of the breech
5. I drilled and tapped a hole in the 12"-long barrel and added a screw to it (making sure that it did not protrude into the barrel)
Edited by CaptainSlug, 04 September 2008 - 05:21 PM.