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Old 11-16-2006, 11:18 AM   #1 (permalink)
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Need help my latest project was a complete failure (VSC pumpmag)

So ive been building a Stockclass pumpmag for several months. Bought alot of new parts, rail, cci 12 gram adapter, cci 15 round feed and feedblock, benchmark asa. searpin, sear, Modified a old minimag body to accept the cci feed parts. also cut down the feed to 10 balls becasue the 15 was to long. bought a new pumpkit for it. and used a old valve since they never go bad.

The problem is after all the work, time, money it only gets 5 or 6 good shots off the 12 gram if that. After that they just roll out the barrel if it will even shot. I was hoping to get 15-20 shots out of a 12 gram. Its the first paintball project gun ive been this disapointed in. It will at least make a nice wall hanger.


The setup is a vertical 12 gram as a foregip, microline to the valve, the valve as it sits now consists of a lvl 7 minimag front and a ans back half, i use a old j&j brass barrel.
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Old 11-16-2006, 12:17 PM   #2 (permalink)
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Automags seem to be hit or miss when it comes to efficiency off a 12g. My only suggestion short of trying a different valve would be to figure out a way to mount the 12g changer sidesaddle to the valve so that you're not having all that expansion space in the macroline to the valve. Not sure if that is going to really make much of a difference.

I'm not real familiar with how pump mags operate vs regular mags. Is it still blow-foreward with you having to pump the bolt back to the rear? Does it still use a standard bolt spring? If so, maybe using a lighter bolt spring would require less CO2 to push the bolt foreward, increasing efficiency. If a pump mag uses gas to move the bolt, that's probably where you lose efficiency-once the bolt is foreward, it should take roughly the same amount of gas to propel the paintball out the barrel as most other pumps.

Never seen a pump mag except pictures, just conjecturing based on what I know about semi mags.
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Last edited by Dave Cameron; 11-16-2006 at 12:26 PM.
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Old 11-16-2006, 12:23 PM   #3 (permalink)
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one question


what type of air line are you using to run from the asa to the valve?


also is your valve an older one?

newer classic valves seem to be more efficeint
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Old 11-16-2006, 12:59 PM   #4 (permalink)
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im using micoline between the valve and asa. i figured the less volume would help. The age of the valve i really dont have a clue. I bought is used. Its a 4 star minimag valve. Ive also got a standard AIR valve and a Micromag AIR valve I could try.

the function of a pumpmag is the same as a normal mag. same bolt spring. just there is a wave spring behind the bolt to make it so it doesnt cock until the pump is pumped. remove that wave spring and the gun is back to a a semi. I do have spare springs from a lvl 10 kit. maybe trying to mix and match them may help.

Im also thinking that the ans back is hurting the efficency due to it milling inside.
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Old 11-16-2006, 01:02 PM   #5 (permalink)
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You never mentioned if you've chronographed the gun yet or not. That would be the first thing I would do.

How old were your 12 gram cartridges? Sometimes they leak as they get older. Trying a new batch can't hurt.

You can very easily mount a 12 gram changer to the side of a classic rail. I'm not sure which one you have already, but a lot of 12 gram changers have an outside diameter of 1". A classic rail has a .22 dovetail scope rail build into each side. A lot of people don't realize that anymore. A scope ring is all you need to mount it right under or around the valve.

I've also heard of people putting a wire inside the hose from a 12 gram to the valve to reduce the space inside.
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Old 11-16-2006, 01:22 PM   #6 (permalink)
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RRFireblade apparently had some success modifying a Pump Mag for efficiency. Didn't sound like a DIY for the rest of us, though.
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Old 11-16-2006, 01:31 PM   #7 (permalink)
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Quote:
Originally Posted by cougar20th View Post
Im also thinking that the ans back is hurting the efficency due to it milling inside.
that's came to my mind.
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Old 11-16-2006, 02:58 PM   #8 (permalink)
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Quote:
Originally Posted by cougar20th View Post
the function of a pumpmag is the same as a normal mag. same bolt spring. just there is a wave spring behind the bolt to make it so it doesnt cock until the pump is pumped. remove that wave spring and the gun is back to a a semi. I do have spare springs from a lvl 10 kit. maybe trying to mix and match them may help.
If that's the case, I would think that the lightest spring would be the way to go. You don't want it to recock anyway, so you just need something to keep the bolt from slamming into the body. Harder spring=more resistance=more gas used to move bolt. I'm not really sure how that would effect velocity,etc.
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Old 11-18-2006, 01:17 AM   #9 (permalink)
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Quote:
Originally Posted by Dave Cameron View Post
If that's the case, I would think that the lightest spring would be the way to go. You don't want it to recock anyway, so you just need something to keep the bolt from slamming into the body. Harder spring=more resistance=more gas used to move bolt. I'm not really sure how that would effect velocity,etc.

It doesn't really work that way, and you need the spring pressure to keep the bolt back enough to keep it from leaking when uncocked. A pump mag is kina a fine line tuning-wise - straddling the edge of a semi just barely messed up enough to shoot "like a pump", but not messed up enough to not actually shoot.


My input into the efficiency problem: The ANS mod is hurting your efficiency badly. It's kinda the side effect of what they were designed for: higher flow to prevent shootdown and lower the operating pressure a bit. Try using an unmodified classic valve and that should boost your efficiency significantly. It won't be "efficient" really but you should get at LEAST 15 or so. And check your velocity. 270-280 is ideal if you're shooting for efficiency.



wow. think I could've said "efficiency" a few more times?
efficiency
efficiency
efficiency
efficiency

I just typed all those. Copying and pasting would've been better for efficiency.




















efficiency
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Old 11-21-2006, 09:17 PM   #10 (permalink)
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i second the idea of using a stock valve back, but normally that only accounts for 1-2 shots per 12g of efficiency. something else is very wrong here. You've either got a huge mismatch on paint sizing causing either a ton of friction and burning up the co2 faster, or a tremendously loose bore, letting it all go right by. i'd also look at the possibility of the spring not quite pushing back enough to seal, so you may have a leak and not be aware of it.

i normally run a 12g from bottom lineASA into a vert reg and then into a massively ported valve body, and i usually see 18-20 shots at 265-270FPS. trimming it all down to a stock body and just a 12g into a backbottle ASA only nets me 22-23 shots. from a relative standpoint, most of the expansion area is in the chamber behind the bolt where you cant affect it anyway.

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