Breech Loader (My Way or the highway)
Shopping List (Materials)
Number of: / Description: / Application:2 / ¾”-1” Bushes / Threaded adapter-barrel joiner
1 / 1” Threaded adapter(valve socket adapter in plumbing lingo) / Valve-Barrel receiver
1 / 1” Socket / O-ring sealing flange
1 / 3/16th drill it (longer than the threaded adapter width) / Drill bit & locking shaft
1 / ¾” PVC / Barrel + bolt handle
1 / »1” O-ring / Gas seal
1 / ¾” 90° Tee / Operating handle mount
2+ / ¾“ sockets / Barrel supports
Below is a step-by-step process.
1. VERY CAREFULLY, grind the ¾”-1” bush down so it will slide into the socket with little resistance. I did this by using spacer washers to center the bush on a bolt and then spin it in a drill, slowly grinding it on a bench grinder. Grind the BREECH END of the bush into a conical shape (»45°), the conical shape will help the breech slide into the threaded socket.
2. Glue the ¾”-1” bush onto the end of the barrel. Get a thin coin/washer (»1mm thick) and drop this into the threaded adapter. Slide the breech into the threaded adapter socket and tape it there to stop it from moving. Use a bench vice or similar to hold the assembly while you find the EXACT center of the socket (length ways and width ways), after the exact middle is found use an appropriately sized drill bit (I used 3/16th) to drill a hole in this position directly through both the threaded socket and bush-barrel. As long as you test the fit of the bolt (I used the drill bit that I drilled the hole with as my bolt) you can now remove the tape and pull apart the two fittings.
3. Now comes the really tricky part, you must cut or grind the PVC bush-barrel away to create slots for the locking shaft (cut down drill bit/bolt) to slide into. To make it even better these grooves must follow the hole diameter and positions perfectly (or very close to). The first groove goes from the end of the bush (breech end), perpendicular to that surface, to the two drilled holes. The second ‘cut’ goes parallel to the breech bush face so it will lock. I accomplished this by making a guide out of flat steel, Get a piece of ¾” flat steel and bend it 90° with a slight rake to one side or another. When you clamp your barrel-bush assembly into the vice, clamp this in beside it lining the hole up. All you need to do then is slide the dremel along it to get a good, straight cut with the rake going forward (towards the muzzle end). You can now remove the coin/spacer that you put in the threaded adapter in step 2.
4. If you did it correctly you should be able to push the barrel into the socket (with the bolt and groves lined up) and rotate it into the locked position (mine is rotated about 45°), with the rotate motion pulling the breech together further (from the pulled in position) by 1mm because of the rake forward. If you cannot do this, check for touch points on the inside of the grooves and file these further to increase the clearance, to allow the locking shaft to slide without binding. Cut the drill bit to length and insert it into the holes in the threaded socket, tape it in there.
5. Now that you have a barrel-bush assembly capable of opening and locking into a threaded adapter socket you will have to make it seal so not too much gas leaks. This is where the 2nd bush and 1” socket come in. Carefully grind/sand out the bush so it slides over the barrel (it is going to be glued so don’t go too far with the grinding). Cut the 1” socket in half and grind/sand the burs from the cut.
6. Slide the 2nd bush onto the barrel down to the breech gluing it there, against the 1st bush. Lock the breech together and glue the socket onto the 2nd bush so there is an »1.5mm (»50% of the O-ring thickness) gap between the threaded adapter and the socket edge.
7. Allow this all to dry for an hour or so, you should need a break by this time anyway. After letting it sit while you had your break, pull the assembly apart and stretch the O-ring onto to the ¾-1” bush with the slots in it so it is sitting against the 1” socket.
8. You’ve now finished the hard part, all you need now is attach an operating handle. You can add any type you want but I will describe mine here because I think it was very successful. Grab the ¾” Tee and draw a line down the side of it, approx ¼” from the side center away from the 90° branch. Do this to both sides, when finished the Tee should hold onto the barrel by friction when pushed onto it. Experiment with bolt positions, finding the best spot for you, there are only two constraints--the length of travel by the barrel (when the bolt handle hits a barrel support) and How far the barrel must be rotated (just use your common sense).
9. After selecting an appropriate handle position draw a line around the Tee, and glue it in that position. Cut a short piece of PVC for the actual handle and push this into the Tee (I glued a cap to the end of the handle for looks).
10. To support the barrel use two or more 3/4 “ sockets with the stopping ring and centers ground out of them so the slide on the barrel easily. Attach these anyway you ca so they hold the barrel on the gun, silicone and a cable tie works good.
11. FINISHED…… about bloody time.
Theory of operation:
The gun is assembled with the 1” threaded socket in the outlet of the valve, and the chamber on the other side of the valve. The barrel is unlocked and moved forward, this allows a projectile to be inserted into the breech end of the barrel. The bolt handle is then moved back and rotated down to lock the barrel and threaded adapter against the O-ring with a small amount of pressure (it may be helpful to add a small amount of grease to the seal to allow easier interaction with the barrel).
With an air charge the gun is ready to be fired. The system of operation would go: (1) Charge with air, (2) load projectile, (3) aim and (4) fire. The bolt-action breechloader works best with flare type projectiles.
Glossary:
Breechà‘rear end of the barrel where projectiles are loaded’, ‘end of barrel where valve attaches to barrel’, ’rear of barrel where projectile sits ready to be fired’
RakeàContext: jig for cutting socket. ’Rake is a slight forward angle used on the guide, to cut the horizontal slot that compresses the O-ring for a gas seal on the rotate motion of bolt closing’, ‘the rake allows cammed rearward movement of the breech to add leverage, which squeezes the O-ring tight’
Conicalà’shape of a cone’, ‘something with an angled cut towards a point in front of the object’
Bloodyà’Australian colloquialism’, ‘mild swear word, equivalent of “damn it”’
SEND ME AN E-MAIL IF ANYTHING DOESN’T WORK OUT OR THE INSTRUCTIONS ARE FLAWED, I WILL TRY TWO HELP ANY WAY I CAN.
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Images of where cuts/ holes are made in the PVC fittings:
RED = Cut
BLUE = Hole