There is a Youtube channel that I follow called "Wranglerstar" that just posted about a problem he had with two 30-06 cartridges failing to fire in his granddad's Remington 721. One is a rather crusty looking LC '54 and the other is R-P which he says is also old but looks clean. The rifle has a history of failing to fire for his grandfather in -18F weather in Easter Oregon some years back that may or may not have been caused by a dragging firing pin as determined and worked on by a gunsmith. The problem with Youtube is that everyone is an instant expert on everything and one guy even blamed the issue on surplus ammo that was make in Korea. If you have 4 minutes pop on over and watch the video and see if you can't provide quality suggestions to help sort out if it is bad ammo or an unreliable rifle. As far as I know he lives in the area around White Salmon so if you're local to that area and want to help out in person I bet he'd happily take the help.