Just a hypothetical eample let's say we start off with a basic weapon, say this's one......
https://en.m.wikipedia.org/wiki/M1911_pistol#/media/File:M1911A1.png
You decide it's time to mod it so you craft or buy
extended barrel
Suppressor
Pinpoint laser
Flaslight
Reinforced frame
Selectable semi/full auto parts
Telescoping stock
What you end up with turns into something like.......
https://www.pinterest.com/pin/459015386991543610/