There are so many aftermarket GLOCK part suppliers that you can build a COMPLETE pistol without having a single (not ONE) factory OEM part in the entire gun. Not a spring, not a pin, not a mag housing, nor firing pin, nothing, nada, that HAS TO come from the factory. As far as aftermarket stuff goes, with the exception of the 1911 & AR, I don't think there's ANY GUN with more available. Can anyone think of one? Oh, maybe the Ruger 10/22.