I'm sure there is a reason for the stringing. If it's happened to your rifle, it has happened to others. I typed it in Google and there are many with the same problem. Could be firing pin problems, bedding problems, barrel problems, bolt lug contact problems, etc.etc.
I haven't reloaded in about 15 years but still have all the equipment, 2 rock chuckers, some smaller presses, a A2 if you know what that was, seems to remember the case trimmer was Forester? Inside and outside neck reamers, primer pocket cutters etc.etc. Few different powder throwers, Lyman, Redding, Belding and Mull, i used to think consistent volume was more important than consistent weight, though i used to use mostly stick powders.