I sanded the CPVC barrel to fit inside the PVC sleeve. I started with 60 grit sandpaper, wrapped around the CPVC. Use several different motions, alternating regularly. There is less chance of the sliding area turning out irregularly shaped that way. I alternated combos of hands, which end I held, up & down or twisting motion and grip. I sanded until it started to fit. I then went up through a few grits ending with 240. One trick is to cover each end of the sliding area of the CPVC with duct tape to avoid making those areas too small. That would leave a leaky breech. Just remove the tape from time to time and sand those areas separately. Once it was done I went over it with a manicure sanding sponge to give it a smooth surface. It should take about 1 1/2 - 2 hours to sand. I probably spent as much time sanding with the rougher grit as I did with the finer.
Here I fit the dartstop. I used a finishing nail I found in my parts jumble. Measure, mark & cut it carefully to insure that it does not stick out past the PVC.
Melt that down into the end of both the sleeve and barrel until it is sunk in. I used a 30 watt soldering iron. I held it in place for a minute while it cooled down.
Undo everything and clean up the burnt plastic. Mark the area of the back of the barrel that needs to be removed. This will allow the barrel to spin a bit, letting the locking lug sink into it's slot. I removed the material with a file. Glue the nail in.
I made the locking lug from some scrap PVC electrical conduit. I cut a small chunk of material to match the width of the opening.
Now mark the barrel for the locking lug. Pull the barrel out and file a notch for the lug. Go very carefully here as the location of the notch will determine how tight your breech seals. A tight fit will ensure a strong lug. Cut the lug to size.
Next I marked, started and filed a small slot for the locking lug to mate to. Test fit the lug to make sure that everything is tight. File and fit the lug, slot and rear mating surfaces carefully. Clean everything scrupulously. Make sure to position the lug so that the barrel will rotate properly in the slot. Glue in the lug with epoxy or solvent weld it in place. If need be the lug can be dremeled away for servicing, replacement or adjustment.
Grease it up well.
Pop it on your blaster and give it a whirl! I added a piece of the NF's stock barrel as a front sight.
It opens 1". There's an additional .75" to jam the dart into before the dartstop. I pretty much matched the opening size to this blaster. A breech for a BBUMB would need to be made longer I guess. Here it is with a 1.4" dart loaded.
Edited by iamthatcat, 29 February 2012 - 02:07 PM.