[parttime]

Accuracy and precision have different variables.
In order to measure the precision of a firearm/cartridge combination you first have to eliminate the inaccuracy of the shooter.
You can do this by holding and firing the firearm in a bench vise of some sort while using a selected group of cartridges.

Firing X number of cartridges at various distances at seperate targets, measuring their point of impact as discribed in an earlier post then switching to a different set of cartridges and repeating.