If there is a 10mm to .40 S&W conversion barrel and the stock 10mm mags work with the shorter round, could there be a .45ACP to .45GAP conversion barrel and the G21 mags work with the shorter GAP rounds?? Many people do not want a G37/38/39 but would't many try a $125 ~ 165 conversion barrel?? I would and then maybe sell my G37!! Glock may not be happy. Chris Wanna kill these ads? We can help!