The bolt on a Savage 220f is forward cam operated. What that means is when you go forward, right up about to where you rotate the bolt down, the cam sets the firing pin back. It doesn't matter how "hard" you pull on the bolt. If you got it back far enough for the extraction/loading then you were pulling as hard as needed. It sounds to me like you have gotten a rare problem with a Savage. Weak firing pin spring or for some reason on a reload the timing is out and the forward cocking cam is not set in time. It doesn't really make sense to me that it's only on followup shots. Seems it would be all the time. But such is the way with anything mechanical. Murphy's Law and such.