Originally Posted by MTS532
You're testing the gun for reliability and for accuracy at different ranges. You should use the magazines you intend to use with the gun you carry.
In this way, the gun and the magazines are tested for reliability and you will have some idea where the rounds will impact at different ranges.
This. Just because the mags, ammo etc. are marked Glock, Winchester, etc. doesn't mean you can't get a lemon. Test the gun and mags you intend to carry, and try to use ammo from the same lot you tested when you load your mags for carry.
Test it enough until YOU'RE comfortable. The reality is that if there is a problem, it will likely surface very quickly and consistently.