To begin with, this breech size is made with 1/2 CPVC barrels and couplers in mind. A 1.5" PVC bushing with the hexagonal portion cut off is an ideal size for squeezing 3 CPVC couplers into the end. I filled up the gaps with liberal amounts of e-putty/goop/hot glue.
This then mates with a piece of 1.5" PVC pipe. I liberally sanded both the insides of the bushing and the outside edge of the PCV pipe. The mating depth is very shallow so that the breech can hinge. An appropriately sized o-ring goes in the breech to help provide seal.
The whole assembly is held shut tightly with these clasps. Cheap and available at any hardware store. I held them on with e-putty. Unfortunately, due to not measuring very carefully on my prototype, as you see in the pictures, I have to hold the clips down harder with a rubber band. Otherwise they can spring loose if you hit the gun on something. I find that the rubber band placement is also helpful when closing the breech back up, since it reduces the amount of hand motion required to operate the clasp.
For the final assembly of the gun I also opted to "fix" the lower clasp. At first I tried some less effective methods of more or less immobilizing portions of the clasp. I settled on e-putty in one place- the part where the latch of the clasp contacts the catch on the front of the breech. It will still break open as desired, but has less "floppyness" than with an un-fixed clasp.
Here are some pictures of the WIP gun the breech is currently attached to:
Note the stock is unfinished.
For those who'd like to know a bit about the breech's performance:
It's very easy to operate, you simply unlock the top clasp and the barrel flips down. Insert darts, flip the barrel back up, lock the clasp and fire. It's pretty quick and easy to use. For the moment the breech does have some leaks due to improper spacing of the gasket such that it does not fully engage with the PVC pipe face. I intend to fix this with some kind of shim to compensate for the depth problem.
Right now, with a fully pumped Pulse Strike tank attached and 2 foot CPVC barrels I am estimating an average range in the 70-80 foot range fired flat, even with leaks.
Edited by arfink, 03 December 2010 - 11:54 AM.