Also:
Receiver plate (e.g., Magpul ASAP etc)
Mag catch (minor modding may be required for smooth operation)
Barrel nut
Takedown pins
Castle Nut (buffer tube)
Also haven't tried myself but Qlong was telling me RS fire selectors will work, however some modding is required to some of the internals (with a potential of FUBARing parts if not done right), so safer sticking to airsoft parts unless absolutely necessary.
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