AF, about 30 years ago there was an article in (I think) Outdoor Life or Field and Stream magazine titled "one shot zero." The method it describes involves bore sighting first (if you have a bolt action), then taking a single shot at short range (25-30 yards), then securing your rifle in a vise or another solid mount, then turning the elevation and windage to move the crosshairs to the hole you just created. If you can do that without moving the rifle very much, your next shot will be very close at 100.
I've been using this method all these years and there's no telling how many 100's of rounds it's saved me in that time. I swapped a barrel the other day and had to re-zero, and I was on in just three shots total. I let the barrel cool and shot a 3-shot group to confirm, and I was done. I left the range 24 min. after I arrived.
It's a brilliant method. I've taught this to dozens of people over the years and it always opens their eyes.