I spent a lot of time doing just that about 2-3 years ago. I bought cases (crates) of 8X57mm Yugo (I think) surplus ammo and some "spam cans" of 7.62X54R. Accuracy was horrible, so I started pulling and measuring and weighing.
A few things that I found;
The 8X57mm bullet weights varried from 195gr to 201gr (198 nominal), so I seperated them into groups according to weight. The powder charge weights were also all over the map. I reused the powder in commercial brass (reduced the charge and worked up a safe load) and reused the sorted bullets. Accuracy was VASTLY better.
THe 7.62X54R bullets varied in weight, but not nearly as much, and they were sorted into groups as well. The powder was reused in commercial brass with the sorted bullets and accuracy again improved markedly.
As a side note, during those experiments, I found the powder in the 7.62X54R surplus ammo to have a burning rate identical to a lot of IMR-4895 that I had on hand. Chronographed charges of both powders had an average muzzle velocity within 10 f.p.s. of each other.
In the end, I feel it was worth it. I was able to use the (then) cheap surplus ammo for components to shoot decent groups instead of just burning powder and not hitting much. Plus, I like to tinker and experiment.
W101