Loosey goosey is correct for a reason- to fit all rifles chambers. So the standard to figure out factory rounds to use is to buy a few different boxes and see what your rifle likes then buy more of the same lot numbers.Wow DeerDon And Xjon good stuff. I was reading the Barnes Data on the 243 TTSX and TSX and the recommended loads , COAL, BC, and Density. How much has your actual vs what Barnes recommends differ. All good stuff and very much appreciated. Now I have to get my beak wet and actually do this. I guess the factory stuff Is loosey goosey.
In regards to loading myself I don't go by manufacturers recs in seating. I look at maximum length for my rifle (at lands) and magazine fitment. If it doesn't fit in magazine-no sense in figuring out how it works with long seating (talking hunting here). Then I will load several rounds with different seating depths and see how my rifle likes the jump. Have loads with .002- .040 jump.
BTW this I do after I have chosen powder charge and also looking for pressure signs with changes in seating.
For measurement I use the hornady bullet comparator gauge which measures from ogive vs tip of bullet.