Current version: REV0.1.X

This is a MAC-11/9 Upper Receiver reference model produced in the same manner that I put together my G19 Gen 3 Slide reference model. All measurements were taken from a physical and functional MAC-11/9 upper receiver assembly (regrettably of unknown origin) with a Grade A granite plate, height gauge, gauge pins, gauge blocks, sine bar, calipers, and so on. The motivation for why I put this together was twofold: I first and foremost have a desire to provide quality resources for arms development, and second, I did not see a terribly wide range of available data out there, and that which I did see did not inspire confidence as to its accuracy or fidelity.

The upper receiver model can be folded out into sheet metal flats. The barrel model is threaded, rifled, and headspaced, but please make sure to check for yourself if you intend to produce barrels according to this spec.

It is also worth noting that all of my previous projects (with very limited exception) have been published under The Unlicense, which is a public domain dedication. This project and all others going forward will be published under CC0 1.0 or newer for purposes of greater legal defensibility. In essence, CC0 does what The Unlicense sets out to do, but better. All of my projects forever and always belong to the public domain.