Lefty- your welcome... I have spent 10 years making mistakes, so I have some advantage in diagnosing them
Good advice by duceman regarding seating resistance "feel" when seating. I always start the bullet, then turn it about 1/4 turn and complete the seat with another stroke. Seems easier to feel the difference that way compared with a single stroke.
Also reagrding "feel"... seating primers is important.....I like the old Lee autoprime because it has a long stroke --- Just recently bought the new version and it has a much shorter stroke and much less "feel". It is possible that when working up a load that some may have been a little hot which changes the diameter of the web (and of course, the primer pocket)..so some brass in the same lot you have fired may be a bit larger at the web (as witnessed by an easy primer seat). This has potential to be more of an issue with those who neck-size only.
Personally, I keep my brass in lots of five when I find five that shoot the same POI.
EDIT: Every little positive "change" can make an improvement in loading. It is much more difficult to go from getting consistent 1" groups than it is to get consistent 1/2" groups. The latter is a bit more challenging than a lot of shooters believe.