Does any one know if a bore up kiit gives you more range or fps?
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I think Bore-up kits are used to match the volume of air pushed within the cylinder to the volume of the inner barrel. So you use a bore up kit when you dramatically increase the length of your inner barrel. I don't think it increases range or fps. Basically you don't need it unless you upgrade an m4 to a psg length barrel or something like that.