Group size as a measure of ammo precision

[Nap Mag]

Specifically inquiring about rimfire but I guess this applies to centerfire as well. When comparing different brands of ammo in terms of precision, why do we measure group size as a whole instead of just the vertical dispersion? Isn’t anything pushing the POI left or right a consequence of rifle or shooter and NOT of the ammo? Sort of like measuring MV at 600yds in terms of how much deviation from the watermark, but not caring about dispersion in the horizontal plane.

 

[Rearden Steel]

While I am not an avid rimfire shooter, your question is interesting. I think that can be boiled down to whether or not a horizontal deviation can be attributed to the manufacturing process.

The answer is that manufacturers tooling can and does wear in more than one way. Not to mention specific operator deviation. The short answer is that those variables can and do contribute to horizontal dispersion. Whether or not it is more than your contribution would depend on you. But make no mistake, nobody’s manufacturing/quality assurance processes are perfect.

That said, I am undoubtedly the most influential component of completing an excellent group.

 

[LDHunter]

Ammo can be so good in one rifle that it shoots one hole groups and all over the place in another rifle so it's certainly NOT all ammo.

There are way too many variables to try to pin it down to only one.