Re: Rule of Thumb?
A few things I have found for tightening up groups. the only rule of thumb is consistency, consistency, consistency.
After that, make sure your neck tension is the same from round to round. Also I have adjusted groups by making the necks a bit tighter or a bit looser in .001" increments. Sometimes you must anneal your case necks to get consistent neck tension. Always at the very least brush out the necks after each firing, uniform primer pockets, deburr the flash holes, keep the necks the same length, if you neck turn then watch for do-nuts, minimize runout.
Most flyers come from either shooter error or the barrel is undergoing some heat issues. If youre shooting on bags and the rifle doesnt ride the bags consistently, you can get flyers. If using a bi-pod and you dont hold it just right and let her recoil differently, you can get flyers. If you apply too much grip or just plain inconsistent grip pressure or cheek pressure or even shoulder pressure, you can get flyers.
When using a properly developed load and the procedure is consistent, flyers are rarely the result of the load. It is ussually the nut behing the trigger.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.