From what I've read...
Glocks and other modern guns are relatively easy to make (patents, etc. aside) as they are designed to be mass-produced by CNC machines and function with generous tolerances.
The 1911 design stems from an era where machines would rough it out and skilled human gunsmiths would do the final steps. There was a lot more human hands-on in that era. Tolerances were a lot tighter.
With 1911s, you run into tolerance stacking (the combined sum of all variance) which may not be obvious if each piece is in spec. It's a more difficult gun to manufacture because it's a less forgiving design.
The big name manufacturers start with a base of many years of accumulated knowledge about 1911 quirks that a newcomer is unlikely to have.
OK, so that's the sum of what I've read about making 1911s...I'm sure someone will correct anything I've misunderstood.
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