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Thread: Shimmed Pump Cup Reduced Speed

  1. #11
    Spilled Milk
    So just being curious, but what do they do about the 1377? And I guess the same deal goes for the .22 version of the QB78. It simply just doesn't break the Non-PAL limit as well? From what I understand, the .177 QB78 does not go over 590 fps. Is that right? (I love my QB78 too much to dare try and mod it. Bought the seal kit for it and it's still sitting on the shelf. LOL)

  2. #12
    Administrator AirGunEric's Avatar
    Join Date
    Sat Dec 3 2011
    Somewhere Out There
    They don't do anything- the native 1377 uses the same transfer port as the 1322 (efficiency and tight engineering take second seat to keeping costs down in manufacturing). The detuned 1377 for Canada has the vented valve and a restricted transfer port (which actually works better than the native version unit in a non-detuned gun). However, people tend to believe that the "best" engineering is done by the factory, despite examples in every industry/manufacturing facility where this is not the case.

    Two guns with the near-same makeup, one in .177 the other in .22- the .22 will shoot slower because the pellet weighs almost twice as much (on average). Airguns should be measured in FPE to make proper comparisons, not velocity and caliber. A QB78 puts out just under 8fpe no matter what the caliber- meaning 498fps using 14.3gr pellets, 670fps for 7.9gr pellets- assuming all other factors are equal, which is more theoretical than true as both caliber rifles only differ in respect to the bolt probe size (and of course the barrel). The problem with .177 is they typically run out of barrel (i.e. the pellet is long gone) before the propellant (Co2, air) pressure runs down, so they tend to waste more propellant and put out less velocity than one might expect using a strict fpe comparison to a .22.
    I'd say I care- but I'd probably be lying...

  3. #13
    Spilled Milk
    "efficiency and tight engineering take second seat to keeping costs down in manufacturing"

    That's what sucks about all manufacturing. Nothing is done for the consumer. It is all for the profit. Some people just don't get that. Once upon a time though...

    Anyways, yeah we understand the whole FPE thing and it is best measured over the entire shooting distance. That starts with muzzle velocity. Then you can start calculating FPE at every meter of travel. Because that is where the caliber matters regardless of the FPE.

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