Mag Shims

Discussion in 'Gas Powered Guns' started by Automobilie, Feb 18, 2020.

  1. Automobilie

    Automobilie Active Member

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    Mag shims can greatly improve the seal between gas magazines and GBB's. The following is a magazine from a KWA ATP, which is notorious for poor seals and performance. Better seals between the mag and cylinder as well as a good piston head seal make for far higher efficiency and performance.

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    However, when installing the shims techs often forget to modify the seal to actually allow it to sit higher and may be best to remove material from the top edges of the seats.

    I found that a Dremel and cut-off wheel works well for "grinding" rubber edges and seats.

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    This means the seal can sit higher without compressing which can block the effects from the shims.
     
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  2. aotsukisho

    aotsukisho Well-Known Member

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    Would lapping the nozzle surface provide any performance gains as well? Either paired with this mod or with stock height gas route packings
     

  3. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Nope...there is not much there to improve performance.

    2 degrees difference and you get better performance. Have you thought about using Propene?
     
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  4. Automobilie

    Automobilie Active Member

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    I actually just switched a mag over to a little CO2-Regulator setup. Propane has been really frustrating with how much the PSI changes just between shots. I'd set the hopup for one day, the temp drops a few degrees, and have to readjust again. Then there getting a consistent fill and any jams resulted in purging all gas. Got 7 mags off a single 12g cartridge at a very consistent PSI, so likely going to stick with it, but might need to change some o-ring materials out, because apparently CO2 can 'carbonate' the ones I had; as in fizzy taste and swelling!

    The mag shims made a pretty noticeable difference for the ATP's.
     
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  5. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    I need to preface that mag polishing for TM won't do much...other mags like ones Made in China. You may find some improvement.