TM pistol hop ups are compatible across the board, all TM pistols and VSR rifles use the same hopup rubbers and barrels except for the M92 and the Desert Eagle I believe. KJWs are mostly TM clones. WE are usually TM clones, but their single stacked 1911s have lower frames that are not compatible, and neither are the magazines. KSC = KWA. NS2 and System 7 are the same thing. KSC's usually just shoot at a lower velocity.
With GBBR's there's virtually no internal compatibility between brands, unless it's a WA spin off like G&P
If you ask a more specific question I can probably give you a more specific answer.
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Last edited by Disco_Dante; August 15th, 2011 at 10:44..