Air Gun Home :: View topic

rsterne · Moderator

I've been thinking for quite a while about machining a custom tank mounting block for 22XX or QB7X rifles.... I wanted something that was safe to mount and withstand a regulator failure.... and that had a bit more clearance between the barrel and the tank so that a 9 oz. CO2 tank (2 1/8" OD) could be used as well as a 13 to 22 oz. HPA tank and regulator.... I also wanted a built in pin valve so that the tank could be removed safely when full.... I got some 1x2 aluminum and started whittling and this is the result:

The block portion itself is 1.375" long which is just long enough for a three groove Picatinny rail which I machined into the bottom so that a Bipod could be mounted directly there.... the round portion that fits into the Main Tube is 1.2" long and I chose to use the same mounting system that I have on my QB79 Tank Block equipped guns except the mounting screws are 8-32 instead of 4mm.... It has a 3/16" shear pin, plus an 8-32 socket head screw in the top with the head in shear for extra strength.... With this new design, however, there is once again room for two O-rings to seal it.... Cool

The 8-32 screw below the tube on the back of the block runs a small shuttle (still to be machined) which will be sealed by a 1/4" O-ring and depresses the pin-valve in the top of the ASA fitting when the screw is tightened.... To remove the tank, you would unscrew the screw until the pin-valve in the tank closed, and then bleed down the main tube of the gun by shooting.... It would be possible to replace the burst disc with some sort of bleed valve I'm sure.... but you are still going to lose the air in the gun....

I got a bit carried away while I was machining, and drilled and tapped a 1/8" NPT hole for a gauge on the left side and a 3/8" NF blind hole for a 1.8K burst disc on the right side.... They are in the same location (mirrored) and where the chamber is at the bottom of the gauge is where the air passages from the main tube and the ASA meet.... The burst disc hole is connected to this chamber by a 3/32" hole.... I tapered off the top of the block just to remove a bit of weight and for appearance....

There is a lot going on with just this one piece.... but the cool thing about it is that everything I need is there for a CO2, hand pumped HPA (using a CO2 tank), or a regulated HPA conversion.... provided the roll-stamped area (if any) on a 22XX is not pressurized.... The only drawback is that there is about 12 hours of machine work in it.... Shocked