AR-15s

This is a useless argument because eventually we will be arguing the definition of “mil spec” I’ve lost count of how many rifles I’ve assembled and I still have a stack of lowers to complete. All are advertised as mil spec and I have yet to have a single instance of a mil spec part not fitting a rifle.

It's not useless. When people claim it, and then it turns out the bolt was 4130 and was responsible for the blow out that takes out an eye it's kind of a big deal. It happens far more often than people know.