Rational reasons for Legendary items?

I prefer to describe Legendary effects on items as some actual visible aspect not just magic. I suspect others feel the same and have tables of ideas for how certain legendary effects might be implemented? Like Charged weapons having taser-like attachments, quickdraw having optimized shape for a holster, auto-stim armour having a stimpack injector built in.

Some I can’t make work though, and wondered if anyone had any tips or ideas. Some I find it hard to accept at all, like Explosive or Incendiary guns - surely that’s down to the type of ammo? How can a gun add that property!

Can anyone help me out here