I had a batch of 7mm-08 handloads producing duds on game, turned out that my primers were not seated deep enough, as my Lee tool had a stress crack and was flexing under pressure. Also had issues with some 444M Leverevolution ammo in a Handi-Rifle. Gunsmith told me the batch of Hornady ammo they'd sold at that time was doing this in several Hand-Rifles, due to primer pockets cut too deep. Had a 223 bolt action giving light primer strikes and it turned out that a shaving of brass was stuck to the side of the firing pin, near the tip, and was "jamming" on the firing pin hole of the bolt face. Also had a fairly new M77 start giving chronic misfires due to light strikes on my handloads (that had been fine the year before) I'd kept that rifle all year with the bolt raised and slightly retracted on a loaded round (truck gun). The sound of the pin dropping on a dry fire was not strong, so I swapped in a Wolff unit with 25% more power. Seems to have cleared it up, so I bet it was spring fatigue. As for unexplainable misfires, I've probably only ever had 2-3 with a centerfire rifle in 30yrs of shooting.
