Dents in the case shoulder area are really not all that uncommon, especially when fired from semi auto rifles like the M1, M14, etc.
I've reloaded and shot them without issue.
I'd be more concerned about picking up and using range brass (rifle). You dont know its history and where it stands in the end of life department. If your going to use them, I'd do a careful inspection and especially check the bases for signs of case head separations.
I gave up using military brass for reloading a long time ago, mostly due to it being more of a pain to reload, and its shorter life. Good commercial brass will usually out last the military brass by four or five loadings, as long as the case necks survive that long, and you dont have to deal with the primer issues.