Crosman 22XX 88g AirSource Adapter--Part 2

Jumping right back in where I left off...

Spotted with a center drill.

Gradually drilled out the hole to 1/2".

Modified a 1/2" bit to drill flat-bottomed holes. Works incredibly well. I can literally shave brass foil from the bottom of the hole that's less than a hair in thickness. Deepened the hole to 0.493". If you're paying incredibly close attention, this isn't enough depth to get full thread engagement on an AirSource cartridge--it's just enough depth for the pin valve I made to refill my A/S cartridges.

With a small boring bar, I opened the hole diameter to 0.520"--roughly the nose diameter on an A/S cartridge.

I couldn't measure to the very bottom of the hole, so I used a telescopic bore gauge and referenced various depths. I had enough confidence that the bottom was at, or extremely close, to my number.

Need to cut the o-ring at the bottom of the hole for the A/S cartridge to seal on. Made a boring bar from a blank 1/4" lathe tool bit. Used the bench grinder and Dremel tool. Cut it so just as the side bottoms on the side of the hole, the tip has cut the o-ring seat to the correct depth.

Not shown: Bored the hole above the o-ring seat to 0.570--roughly 14.5mm--my tapping size.

Tapped the hole to the o-ring seat M16 x 1.5mm. Used a bottoming tap.



I need a pin to depress the A/S valve.

Spotted the bottom of the hole then drilled about 1.150" deep with a 1/8" bit. Depth not critical.

Used the 1/8" bit as I have some drill rod in that size for a pin. Not shown: Used a 1/4" endmill to make a counterbore as a gas flow passageway. You can see it three or four pics below.

Cut a piece off with some heavy side cutters then flattened one end. Started by holding it with the vise grips, but then I remembered that I have a really sweet set of pin vises.

The pin vise uses a collet to clamp the pin and gave me more dexterity.

Fit an o-ring and the pin, then test fit the A/S cartridge a few times. Tweaked the pin length until it opened the valve just as the cartridge was sealing against the o-ring. I think the pin ended up somewhere around 0.598" OAL.

Another view. You can see the 1/4" counterbore around the pin. It's just space for the CO2 gas to flow out from the A/S cartridge as its valve opens.

Did some more layout and found the centerline on the bottom of the adapter. Picked a spot.

Spotted then drilled with an 11/32" bit. Followed with yet another modified bit to drill flat bottomed holes. Drilled approx 0.260" deep.

Then tapped 3/8"-24. Why? Safety first.

This hole is for a paintball tank burst disk

The M16 A/S and 9/16 valve hole bottoms aren't even with each other . They're offset slightly. Scratched a rough angled line to connect them.

Before I make the connection, I used a homemade pointed indicator to find the center of the 9/16 hole.

Then drilled about 0.250" deep with a 5/32" bit.

Angled the piece and sighted my scratched line with a small machinst square. Then centered up on the 3/8"-24 tapped hole and connected to the opposite 9/16" valve hole with a 1/8" bit.

Test fit and checked for leaks. There's the burst disk on the bottom right of the adapter. A 3K is installed now--same as all PB tanks--though I also have a 1.8K on hand.

Just a quick ad hoc arrangement at the Crosman valve end for pressure testing.

To seal the gun end, I used the front half of the Crosman valve. Added a small bolt with an o-ring at the base of the head to make a hasty seal to prevent the CO2 from escaping at the outward facing end seal. A quick and dirty pin valve if you will.

A drop of Crosman Pellgun Oil at each connection showed only a tiny leak at the burst disk. A fraction of a turn tighter and it held fast.

So, that piece of Crosman valve will be discarded from the design. A threaded tube will replace it and screw into both the gun's main valve body and this adapter. The hard part now will be getting the thread depth and o-ring seats correct so the A/S cartridge sits directly underneath the gas tube. Still a few design decisions, but I'm leaning toward cutting down a 2240 gas tube rather than make the conncting tube 3 or 4 inches long.

More in a couple days.

Crosman 22XX 88g AirSource Adapter--Part 1

Since I'm on a CO2 roll lately, its finally time to get to a piece I've contemplated for way too long now. I've been kicking the idea around for a way to add a small external CO2 tank to one of my Crosman 2240/50 guns. After seeing my buddy Joe's Hammerli 850 Air Magnum, I wondered if I could just use an 88 gram AirSource cartridge. Bruce (aka Mr B) from the Pyramyd Air blog was kind enough to send me some empty Crosman AirSource cartridges to take measurements. Unfortunately, the diameter of the AirSource cartridge prevents it fitting directly in-line with the 22XX valve. It just won't quite fit under the barrel. Essentially, I need an offset mount for the tank to the valve. And that's where the project more or less stalled out. I had a couple ideas, but lack of a suitable piece of raw material and an endless stream of other projects took precedence--until now. I looked at the QB tank block from Steve at Archer Airguns. In unmodified form, that tank block won't work in my particular application without extensive re-work--enough so that it made sense to just start from scratch but with that basic idea. The other issues that arose centered on whether to make a piercing mechanism for the A/S cartridges or make them refillable. Then there was the usual research to determine thread sizes, source pieces, raw materials and tooling...ahhh, you know.

Dave from Radial Grinding was kind enough to supply me with the needed 1.5" diameter brass. Anybody priced brass lately? I need to buy Dave lunch.

After lots of napkin sketches and dragging my feet even more, I decided that the piece was just a bit too long. At full width, this is one heavy piece of metal.

I parted off almost half an inch.

Title this one: Big cut for little lathe.

Crazy. And it worked just dandy. Advancing the cutting blade incrementally in the holder as I cut deeper kept the set-up as stiff as possible.

Faced both ends.

Still wanted (needed?) to take some weight out of the adapter, so I cut a flat.

Without moving the carriage from my final cut, I measured the width of the cut piece in the chuck. Subtracting that from 1.5"--the original diameter of the brass rod told me I'd removed 0.244"--and how much to remove from the opposite side to keep things even.

I touched the stop against the carriage and locked the carriage in place.

Loosened the stop then placed a stack of feeler gauges between the carriage and the stop. The stack of feeler gauges were equal to the 0.244".

Another view.

So the gap to the stop is the depth of the next cut.

Flipped the piece putting the new flat against the chuck.

Then, I just advanced the cut until the carriage bottomed out.

The sides are within just a couple thousandths. Good enough. Next, I did some layout finding the hole locations and depths for the A/S and the 22XX valve thread.

Big markings so I don't do anything (more) stupid (than usual).

After endless centering on the punch mark , I finally spotted the hole for the 9/16-18 valve threads.

Gradually drilled...

...then bored to 0.515"--my tapping size.

Without disturbing the set up in the chuck, I tapped the 9/16-18 thread.

Note the work piece's offset in the 4-jaw. Couldn't turn at anything but the very slowest speed otherwise the vibration got ugly. Could've used a steel or brass packing block to act as a counterbalance--that might have allowed faster turning speeds--but this worked. Just barely.

Threads cut

Still keeping the set-up intact, I bored the relief for an o-ring seat. Matched the original dimensions used by Crosman on the 22XX valve.

One down, one more hole (two actually) to go.

Here's the centering procedure I mentioned above. With a pointed center indicator in the tailstock, the work is adjusted in the 4-jaw and rotated by hand until the center punch has no perceptible run out under magnification.

I'm set up to start the A/S threading next time around.