Another Dry Barrel Modification

[cousy]

After viewing Tromic’s dry barrel modifications I decide to try to make one of my own. My mod is for a 13mm barrel pneumatic using a 9/32nds (7.14mm) shaft. This is a very simple conversion that uses all of the original gun components and it is completely reversible. I modified the nose piece with JB Weld to form a foundation to hold 2 o-rings that are inserted into the bore of the nose piece.
The o-rings and spear shaft need to be waxed with car polish so the epoxy does not stick to them. After the epoxy has dried on both sides of the o-rings pull the spear shaft out and use a dental pick to remove the o-rings; now bore the hole slightly larger so the shaft can pass through easily. Replace the o-rings and use 3M cold shrink tubing to cover the water outlets.

 

[tromic]

Nice job cousy. What size O-ring do you use on the 7.14 mm shaft?

 

[cousy]

I used a 7mm by 1.8 mm when I poured in the epoxy but I noticed during testing on land with a flooded muzzle that a small amount would leak out if I rocked the test shaft back and forth. Now I am using a 6.8 mm by 1.9 mm, this size seems to be working good for me.

 

[tromic]

I used a 7mm by 1.8 mm when I poured in the epoxy but I noticed during testing on land with a flooded muzzle that a small amount would leak out if I rocked the test shaft back and forth. Now I am using a 6.8 mm by 1.9 mm, this size seems to be working good for me.

cousy, this concerns your tovarich like modification. I find out in general concerning dray barrel systems: it is very recommended to empty the water from the gun before inserting the shaft and sealing it, and after that loading the shaft in the water. If not doing so the water that remains in the muzzle would, under high pressure, enter the barrel between the barrel and the piston. The oil on piston becomes milky what means water and oil mixture. I think, this is especially true for dry barrel systems that have small diameter hole for the shaft (tovarich, some kinds of tomba) so the water could not easily escape.

 

[cousy]

If the small amount of water that is trapped inside the barrel does not escape through the small muzzle hole it will try to exit from the exhaust ports that are cover with the rubber tubing. When this happens the rubber will bulge outward and prevent a high pressure build up water in the muzzle area.

The air pressure on the o-ring inside the barrel should always be greater water pressure which should prevent water from entering the barrel.

However, in a couple of months I will drain the oil out of my guns to check if any water has entered into the gun.

 

[azapa]

nice job: simple and creative. Please please do some followups after real testing

 

[tromic]

However, in a couple of months I will drain the oil out of my guns to check if any water has entered into the gun.

I did it and that is why I told you to be careful. The rubber tubing is important.