Paintball to .22 pellet conversion.

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   So for the last 10-ish years i have had a paintball marker sitting in the garage. A hand-me-down from a brother in law that no longer wanted it. Its basic, but reasonable quality and all alloy. It uses co2 and is designed to shoot projectiles.. so.. I started investigating an idea i had to convert the .68 semi-auto marker to .22 single shot pellet. 

Basic idea is disable the blowback, and create a slot for bolt action like a Crosman 2250.

Below is the basic function of the paintball gun:

Then below the idea of the conversion:

First was solving blowback, this system uses a hammer to strike the valve pin, and a flat section on the pin allowing gas to flow through and reset the hammer. 
I filed the flat section rough and filled with JB Weld. When dry file and sand to fit the valve hole, and hope the gas is redirected to the pellet. 
This didnt work 100% as there was hammer bounce leading to a nice farting and wasted gas. enough to open the valve but not reset the hammer. I found there was around 5mm preload on the hammer spring.

Next step was a firmer but shorter spring, coupled with 10-15mm free flight for the hammer. This meant the hammer hit the valve pin then hit the firm spring to absorb the energy rather than throw it back at the pin. 

This worked just enough. Resulted in a hammer that flops around freely, but I can live with that.. 

Next was the breech, this was cut out with a half-buggered drill press, and a $4 Aliexpress end mill bit then filed / sanded to acceptable finish.

Next up is the Bolt; this will use the existing alloy bolt which is attached to the hammer. It was cut in two sections so pulling back cocks the hammer, then push forward to close breach. Filed, sanded and fitted with a neo magnet so the bolt can stay open when loading. 

Simple bolt handle made by a double end thread rod (Aliexpress), and cheap metal guitar knob (Aliexpress).

Cocking slot was precision cut on this same milling rig (cringe now):

But cut ok.. 

Filing will smooth the edges for smooth cocking. This is by no means planned as an exhibition or match grade rifle 

But, this is a bit of fun, and hopefully something functional at the end. Below is where I am at; a functioning bolt action single shot .68 paintball gun. 
(Also shows the 'fuel filter' planned for a suppressor. From.... Aliexpress)

Oh.. the barrel. It is now cut to 19", Crosman 2260 barrel. Good enough for this project. It will be mounted using .68 paintball barrel as a shroud.

NEXT steps involve a little more accurate machining than my hand tools can allow:
- bushes to centre the .22 barrel inside the .68 barrel
- an insert in the current bolt that will be a flow through probe to seal the barrel (like a 2250)
- muzzle end bush will need to be an adapter for the 'fuel filter' supp. 

The above will prove if it will function and to test the power. Updates coming soon. 