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Thread: Retained Air Pumper or PCP With An Onboard Pump?

  1. #1
    Moderator rsterne's Avatar
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    Retained Air Pumper or PCP With An Onboard Pump?

    Is this totally a matter of semantics?.... The pumpers most of us are used to are "pump and dump" where the valve ends up empty after every shot.... Most people know that if you pump too much, eventually you get some air left over, which we call "retained air".... Most of the time this is a nuisance, but by careful tuning you can achieve some cool things.... I have a 2289/2200 based Carbine that is tuned to shoot 1 shot of 600 fps (14.3 gr.) from 10 pumps or two from 20 pumps.... The first shot is quite quiet, and leaves enough air in the valve for a second shot of the same velocity....

    Steve in NC has spent a lot of time developing his "AC392s" (for Air Conserving, based on the Benjamin 392) which have a larger than usual valve volume and a HDD, which you pump to maybe 1200-1500 psi, and then shoot like a PCP, adding air when you have to / feel like it.... By using an RVA you can tune the gun to deliver, for example 750 fps on 5 pumps, 700 on 4, 650 on 3, etc.... Those are "additional" pumps to top the reservoir back up to the design pressure, so they are at the high end of the effort scale.... With careful tuning, you can even get 2-3 shots (more on lower powers) without pumping in between.... This is where the gun begins to transition (IMO) into a PCP with an onboard pump, like a poor mans FX Independence....

    What do you think they are?.... More importantly, do they interest you at all, or do you think a pumper should just dump all the air on every shot?.... I've been reconsidering them lately, and I can see the merit in not blowing air out the barrel that does little (or nothing) to accelerate the pellet.... One thing I did learn in a discussion with Steve is that having the valve in any pneumatic (SSP, MSP, PCP, even CO2) stay open after the pellet has travelled half the barrel length is BAD for efficiency....

    Bob
    Last edited by rsterne; Aug 13 2012 at 10:55 PM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  2. #2
    Administrator AirGunEric's Avatar
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    In my view- it's a good concept- IF you don't mind pumping. I'm not much of a fan (despite personally having 4 pumpers- they just never get used).
    I'd say I care- but I'd probably be lying...


  3. #3
    Senior Member SeanMP's Avatar
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    I like the idea. I have a 1377 tuned to get two shots at 500fps. The only thing that concerns me with that gun is the consistency. I would like it better if the reservoir was large enough to get more consistency. The first shot is dead on but the second can be a little hot.
    In a rifle I think it would be a really cool idea. Again if the reservoir was huge. You would indeed have a self contained PCP.
    Sean

  4. #4
    Wow... The timing on this thread is remarkable. Are you guys psychic? Pardon my total ignorance and high arching learning curve, but, I continue to prove my ignorance with some more stupid questions...

    To wit: You guys are killing me, as a newbie, with the acronyms like PAL and HDD. I know it is more effecient for communication amongst the knowing. It is humbling for those of us in the dark. I aint completely dumb, just mostly, so I will figure it out with time.

    About the thread: just yesterday I saw a youtube of a 2240 HPA conversion kit. I went to the dealers site and could not understand what he was even selling in his "little black tube." He had instructions on tuning the valve stem and expanding the volume, but nothing about how or why his conversion worked and/or if you could "pump" it up.

    This question probably belongs in the PCP section, but, you got me thinking about conversion to PCP, or retained air, by modification. Do any of you have any thoughts on conversions that allow external pumping and retain air? CO2 is very expensive here and tanked air is out of the question.

    If this has aleady be discussed in another section forgive my overlooking it. I am working my way through the past threads and reading as much as I can bear. You all have been giving me a good education and I am grateful for your extensive and well presented research and development. Good work guys

  5. #5
    Member DocGadget's Avatar
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    To me it's how hard the pumping gets. Pumping my air pump to fill one of my wonderful PCP's isn't too hard because I can put my whole weight on it. Pumping a 1377 or a 397/392 over 8 times get HARD and for different reasons.

  6. #6
    Senior Member SeanMP's Avatar
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    Quote Originally Posted by Poor-man Plinker View Post
    Wow... The timing on this thread is remarkable. Are you guys psychic? Pardon my total ignorance and high arching learning curve, but, I continue to prove my ignorance with some more stupid questions...

    To wit: You guys are killing me, as a newbie, with the acronyms like PAL and HDD. I know it is more effecient for communication amongst the knowing. It is humbling for those of us in the dark. I aint completely dumb, just mostly, so I will figure it out with time.

    About the thread: just yesterday I saw a youtube of a 2240 HPA conversion kit. I went to the dealers site and could not understand what he was even selling in his "little black tube." He had instructions on tuning the valve stem and expanding the volume, but nothing about how or why his conversion worked and/or if you could "pump" it up.

    This question probably belongs in the PCP section, but, you got me thinking about conversion to PCP, or retained air, by modification. Do any of you have any thoughts on conversions that allow external pumping and retain air? CO2 is very expensive here and tanked air is out of the question.

    If this has aleady be discussed in another section forgive my overlooking it. I am working my way through the past threads and reading as much as I can bear. You all have been giving me a good education and I am grateful for your extensive and well presented research and development. Good work guys
    Hi Art

    Yes the acronyms. I'm not a huge fan of them because I work for the biggest generator of all time.

    PAL = Possession and Acquisition License and is really confined to those in Canada. Other countries have different wording for their licenses
    HDD= Hammer Debounce Device. Simply a little widget that adds drag to the hammer to keep it from rebounding back against the valve stem after the initial shot.

    We probably have lots of thoughts on external pumping and retained air. Can you narrow it down a bit? I only say this because that one question almost could encompass everything.

    Could you mean internal pumping and retained air? The ability to pump up a rifle using a built in pump and have multiple shots.
    Sean

  7. #7
    Thank you Sean,

    Again, this might belong in another thread, but... The youtube conversion I saw linked to powermax-hipac@att.net, a multi-shot system that was said to allow for an external pump. It was said to convert a 2240 CO2 gun to an external pump LPA (ha ha ha) low pressure air 1000 to 1500 psi gun. I have one 1377 mod and three 2240 mods and was thinking I could save gas with an external pump system that did away with the co2 in one of the 2240 based guns. After I send this post I am going to search the PCP section and see what has already been posted.

    As for your original post I am now seriously considering tuning the 1377 to a retained air 2 shot system. With the FTP and the right spring combination I might be able to squeeze out 2 shots with a stock valve. I have no lathe to gouge out that valve and see no way to really increase the volume. But, I can decrease the exhaust.

    For an HDD I am using a piece of vinyl tubing on the exposed end of the valve stem. I bought a broke one of the poly "little widgets" before ever firing a shot from my 2240. I did find that a lighter hammer spring instantly increased the usable shot thread. I have no results from the vinyl tube idea yet, it just fits the poor man plinker mind set. But, I digress...

    Any links or references to a co2/hpa conversion that can use an external pump, like the Discovery has, would be appreciated. I will go to the PCP thread and read the old posts. I may find what I am looking for there.

    Again, thank you fellows for your time and attention to my novice exploration. Your knowledge and expertice is appreciated.

  8. #8
    Moderator rsterne's Avatar
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    While it has nothing to do with this thread (and I have no problem with that).... I would suggest you PM Gippeto and ask him about the HiPac, he is familiar with them.... They screw into a 2240, replacing the Co2 cartridge with an HPA cylinder with Foster fill fitting.... You can then fill from a stirrup pump (or SCUBA tank).... If you don't have your PAL, you will have to do some experimenting to keep your 2240 under 500 fps....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal:
    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  9. #9
    Member Gippeto's Avatar
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    Dropped him a pm earlier this morning. :)

    (R)PAL shouldn't be an issue in Costa Rica. ;)

    For whatever it's worth, I set my pumpers up as dumpers. Can maintain the variable power aspect of them this way...which is what I liked about them.

    Al

  10. #10
    Senior Member SeanMP's Avatar
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    Actually converting a 2240 to use HPA with an external pump is really easy. You need to buy or make a bulk fill end cap and you need to tear down the gun completely and clean it. Then relubricate with silicone grease. This method simply uses the empty CO2 tube for an HPA reservoir.....thats the bargain basement route.

    Next cheapest is to swap the tube with a larger one from another model. More volume is more shots.

    And then the really slick cool way is adding in the HiPac
    Sean

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