Good tip Rod...
I also learned the hard way once...
My education came from load testing 7mm Nos 120 BT's...
When i loaded the second test ito confirm the results of the first test, i transitioned from one box to another...
I didnt know what was wrong when the second test was all over the place...
...the results of the first test were really solid so i was dumfounded...
So i did the test again, & when seating them i noticed i had to change the seater die but just figured i must have changed it to put it back in the box or something...
So the results of the 3rd test were solid this time also, except at different powder charges....
Thankfully i kept 2 untouched projectiles from the first box & decided only then that i should check them as everything else seemed ok...
One batch was .015" shorter than the other, yet .025" longer in the ogive...
So i had effectively shot 3 load tests with 2 different bullets at 4 different seating depths...
I now measure 10 bullets from EVERY SINGLE BOX now regardless even if same batch number before seating, & i seat them so the ogive measurement is same...
The man who knows everything, doesnt really know everything...he's just stopped learning...