One more thing we need to control for...
Is the manufacturer putting the same pellet in the tin?
I was trying different 8.4s through my 97k, I bought a tin of RWS superfields.
They looked a little different from the standard JSB design, with a longer waist.
Tried them out indoors, they grouped fantastically; "awesome, I'll buy some more of those" I think to myself.
I duly purchase two more tins, same shop, same batch number.
I get to the range and open them up....
Completely different, standard JSB waist/skirt ratio and made of what appeared to be pot metal. I'll leave you to guess how well they grouped.
Trying to correlate down range velocity with a particular batch is all well and good if the thing on the tin is the thing in the tin. I've heard anecdotal evidence of tins filled with two distinctly different weights.
I used to think weighing pellets was for those with too much time on their hands, but now I'm not so sure.