Re: Leupold aftermarket reticle knobs
So they turrents that are calibrated for one load will get you ball park at the given environment you have them made for. If you happen to do anything to change muzzle velocity that turrent will be wrong, how much wrong you are willing to live with. The environment change will also matter but little changes are not as important. What you are shooting, where you are hunting/practicing and what is your acceptable margin of error? Four inches of error on a elk is nothing, on a PD you will have a clean miss.
I help someone setup a 300 RUM for elk out to 600 with a turrent. He hunts one specific area and we set it up for average temp during hunting season. We used chrono numbers shot at that temp range. I loaded him 300 rounds of ammo that are as close to the same as possible. I would bet that will last him at least 10 years of hunting.
I prefer to just use a ballistic program and then dial the "clicks" for that specific situation.