Thanks a bunch!When the bolt has a visible crack or one of the lugs break off. The carrier should never need replacing
Chad in School of the American Rifle has numerous BCG inspection videos . . .
https://www.youtube.com/@InstructorChad
His latest BCG inspection is this one. While most of us wouldn't have the gauges he has, his inspection videos give you a very good idea of the kinds of things to look for and evaluate when inspecting one based on appearance including what to look for and the signs of wear. If you search his videos for "BCG" you'll find he has made many of them.
Some of his better ones
The worst he ever captured on video
Wear is fine. The carrier itself should last a very long time just keep it well maintained/lubed.How or when should the BCG be replace on an AR type, 5.56? Mine is starting to show some signs of wear.