XM15 pump kit project

[SSP REAPER]

I have some of the really thick walled Macroline that I am using, should devolumize more so than the thinner walled stuff. Out of curiosity, should I mainly use this after the reg or before? Seems like before the reg would diminish the expansion of the CO2, but maybe I am missing something.

Is there a link to a discussion about devolumizing? I might need a better grasp of the theory behind this to better understand it.

Contact Loguzzzzzz for more information. He has done it successfully on many, many classic valves.

[OPBN]

I meant the theory behind the benefits of devolumizing in general, not just the valve. I don't truly understand why it helps. I'm used to just the opposite with Tippmanns where you add expansion chambers etc to increase the volume it seems, not to decrease it.

[Ando]

I don't know who came up with the idea of shoving stuff like pipe cleaners, Q-Tip sticks...etc... into the macro-line to devolumise it. All that does is increases the time it takes for air in the tank to recharge the valve due to the BS in the line which I admit, is a moot point when it comes to a pump mag (can't shoot it fast enough) but why do it?

As for the devolumizing of a valve which is where the magic happens. By adding shims to the front chamber, your taking away the amount of air (volume) it uses. One thing to remember, the greater the volume, the greater the velocity and vice versa. One marker operating at 500 psi will fire a paintball at the same velocity as a marker that operates on 250 psi. The 250 psi marker uses a greater volume of gas to achieve the same velocity though.

Now with that being said, by reducing the volume of the chamber, you now need to increase the pressure to attain the same velocity before the shrinking of said chamber.

Note: Volume is constant so no mater how much pressure you input, volume is not going to change. (I think I got that right)



Lets use this animation as an example of the front chamber. Temp has nothing to do with this so just blank it out.

Theoretically speaking. Lets say the to reach 300FPS, the volume of the front chamber needs to be 4 cubic inches (which is where the animation starts at the top) and we need 100psi to attain that speed. Now by reducing the volume by half, the amount of pressure will double to 200psi to attain that same FPS.

But there's a few things you have to take into consideration when doing this with a mag. The achilles tendon for devolumizing a mag is the Reg Piston. We know the piston is only going to take so much pressure before it starts venting out the back so there's a balance you need to figure out. Each reg piston is going to be different (as we've seen on some lvl 10 installations) so trial and error with whatever your using to fill the chamber is something you'll need to figure out.

If I'm correct on what I said before about volume being constant when pressure is applied (it's been a while for me) No mater how high the pressure is increased, the volume of air in a chamber stays the same. I know there was a discussion at one time that increasing the pressure to the marker increases the amount of air the marker uses which is false (if I'm correct that is).

Just look at an air tank for example.

You have a 68 cubic inch tank rated at 4500psi. If you fill it to 3000 psi, is the volume any smaller? No, it's still a 68 cubic in tank.

Again. You have two 68 cubic inch tanks. One rated at 3k the other at 4500 psi. Will you get the same amount of shot's out of both? No you won't and why is that? Because of the difference in volume or pressure?

[OPBN]

Well, I have capped off the reg and using the Bob Long, so I shouldn't have to worry about venting.

[Ando]

Ya...I'm not sure how the cap works but good luck with your setup

In a nut shell. The smaller the cavity the less air your going to use. Someone posted before that they were getting like 30 or so shots off a 12 gram after devolumizing the valve. I've done like 3 of them but never tested it on 12g, I use a 22ci tank on one and 2 3oz bottles on the others.

One thing I did forget to mention. It was a while since I did the mods to my valves so this issue might have been from something else I was working on but I did have an issue of shoot down when I filled the chamber up to much. Again...This issue might have been from something else I was working on so take it for a grain of salt.

I know it had something to do with one of my pump mags and I had set it so i could get at least 5 shots off before experiencing any shoot down.