this is how I fill my pcp with co2

first of all this is the gun

Please note this is a .177 cal with a 55cm (21.6″) barrel.

1. degass it.
2. weight it with its all accessories (fill cap etc). then note it. my pcp’s empty weight is 3962gram. (sorry guys Im live in a metric world)
3. knowing the volume of the pcp’s airtube is IMPORTANT! mine is 160cc.
4. max of co2 volume that can be filled to the airtube is 1/3 by volume. so in this case I can fill my gun to 53.33cc. but of course I CAN NOT SEE through the airtube to check whether it is 1/3 full or not. so the only thing I can do is weighing it. because the SG of CO2 is 1.98gram/cc means I can fill up my gun to 106gram. in this case the full weight of my gun is 3962+106 = 4068.

learn about co2 here:
http://www.warpig.com/paintball/technical/gasses/co2dynamics.shtml

5. connect the gun to this 8kg (18Lbs) NON-siphon tube. and open the valve fully.

Dont worry about overfill as practically ‘there is no overfill by pressure’. co2 pressure at room temp (32°C 90°F) is ‘only’ around 1100 psi.
BUT PLEASE BEWARE of ‘overfill by weight’. But again as the pressure of the airtube is equal with the press of the 8KG tube, there is no way that the co2 will transfer from the bulk to the airtube.

6. Unless: I made the press of the airtube lower that the press of the 8kg tube. this is done by putting some ice to the airtube.

7. IMPROTANT: put my cellphone alarm on for 5 minutes or so. (this only-5-minute interval needed when the 8kg tube is full – 8kg). by the time I took this pics the weight of the 8kg tube is maybe 3 kgs left. So I need more that 20 minutes with 2 bags of ice sandwiching the airtube.

THIS IS IMPORTANT! left an ‘iced’ pcp connected to a bulk fill without something to remind you will lead to overfill by weight, which also lead to disaster!
left them connected and then you forgeting it means the airtube will absorb as much co2 as the ‘ice’ (lower press) can get. but as soon the ice melt away, the airtube temp slowly go back to room temp and so does the airtube pressure. A 150% full rate at room temp (on my case is 32C) is DISASTER! (again learn co2dynamics link above and also this diagram.)

A 150% full rate co2 at room temp, the pressure will raise beyond any pcp airtube can hold!!!!!

8. when the alarm went off, I disconnected it and weighed it.

Sometimes my instinct is bad, I need to connect it again. 🙂 (my gun’s full weigh is 4068gram)

9. after 10 more minutes, now this is a 104.7% (111gram/106gram) full. I will adjust it to 100% full rate by dry firing.

after that all I ve just to do is wait til the temp of the gun go back to room temp. then, as BB said: Hours of fun! lol.

literally with a consumption of 0.5gram per shot I can get 106/.5 = 212 shot!
but please take a look at this diagram:

the pressure of CO2 will decrease below 1000 psi when there’s only 25% co2 left in the airtube. So by mulliplying this number I can get around some 160 efective shot with just one fill! that’s more than enough for a backyard plinking or squirel hunting or even a rat hunt at some chicken farm. hehe 🙂

Note: working with new power plant at 1000s psi is useless without changing the hammer spring. you dont need a strong spring to knock open the valve at 1000s, and if you do with your previous one for HPA is just a waste.

So I picked another similar spring which is softer (the original one is that blue spring) and I started doing some research. I cut this new spring 5mm by 5mm (1/5 inch) to find the best spring length for my co2 gun. working with a chronograph then I found that a cut-down-to 85mm spring is the best: 725s fps with a consumption of 0.5gram per shot.
At first I cut the 1st spring down to around 70mm which I can get a consumtion of 0.4 gram per shot, but the MV is also low: at around 550s fps. But please note that longer spring (more than 85mm) doesnt mean will give you more fps, max mv is always around 725s! with this gun.

🙂