I've searched on this issue and could not find much information as to what the average life span of a melonited barrel vs chrome lined on an AR.
The best and most recent thread I found basically indicated that it was too soon to know. See this thread: https://www.m4carbine.net/showthread...light=melonite
I didn't want to resurrect an old thread so I am starting this one to see if there is any new information in this regard.

