Seems to be a take your pic. No pictures in the following thread so you will have to do some searches, but there does seem to be an issue with Frontier. From looking around it seems 55gr 5.56 was the worst, but not only. And Hornady's response claiming out of battery discharge due to dirty chambers isn't exactly confidence inspiring.
https://www.m4carbine.net/showthread...-5-56-55-grain
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