grouping factory ammunition

[elkins_93]

Just curious. Does anyone else measure with a vernier caliper or other tool and weigh factory rounds then group them into alike groups and see what your weapon performs best with ?

[Hotolds442]

The only time I group ammo is for my 17HMR, I group them by weight. The only factory ammo I've ever bought besides rimfire, is 6.8SPC and I don't sort it.

[Tokimini]

Sorting factory ammo by weight is a waste of time. The only accurate way to sort brass is by internal volume, as the case weight can vary considerably. Factory charge weight can also vary by a fair amount.

[darkker]

To add to Tokimini's points.
There is no one formula that anyone has to follow for cartridge cases, so he is correct, case weight is totally irrelevant. Case volume is what changes burning rates, so measure case volume; or better yet...
NO commercial factory ammunition is loaded with grains of powder in ammo; they load volume. A consistent volume will keep case fill the same, and not aggrevate burn rate variations. So don't load in grains, load volume!
So unless you simply wanted to play QC man: unless you knew the specific metallurgical formula the cases were made of, and knew the powder Nominal VMD, and knew the nominal bullet spread. You can't chase anything definitive in factory ammo, by weighing it.