Re: rimfire .22 misfireing
+2 on the spring replacement. Who knows how many rounds that rifle has seen in its day, or how many times it was stored in the cocked position which could shorten the life of the spring dramatically.
Some ammo manufacturers use primers that require a heavier strike than others. For instance, some millitary centerfire ammo requires 4.5 lbs instead of the civilian standard of 3.5 lbs to set off the primer...I'm thinking the same could be for rimfires depending on their specific setups.