The term mil spec comes from the Technical Data Package or TDP. It’s what the military demands it’s guns to be built to. It includes testing of parts and which materials parts are built with as well as assembly procedures.
Commercial companies are not held to any standard and use the term mil spec very loosely. Choose a BCG that runs $59 off eBay and don’t expect it to meet any Military standards.
On the other end spending $400 on an enhanced carrier with the latest coating on it might get you a better part or it might make the seller a big bonus. Reputable parts can be affordable.
