After mounting your scope do you use collimator, laser, bore sight through the barrel, voodoo? I still end up using a cheap Bushnell collimator, likely because I'm too dumb to figure out if there's a better way. Is there a better way? The Bushnell collimator works, but I'm open to improvements.
I don't bore site at all. Ever. Usually I can get a zero in about 5 rounds or less. Every now and then I get something stubborn but not that often.
The method is pretty easy. Get a big clean target. It can be a poster board or whatever. I have used those big foam boards with aluminum foil stuck to them that you get at home depot but you might not need the whole thing. Maybe half is ok.
Put a small dot on the large target, just enough for an aiming point. This works if you are using a led sled or something like that to hold your rifle during zero. Having a bubble level on your rifle helps a lot.
If you want to be more precise you can put a 'plus sign' on the target for an aiming point but do it with a ruler or something straight, but make sure the lines are square with the edges of your target. If you use the 'plus system' make sure the target is level when you set it up. You can use a tape measure to get it pretty square and a level to set up the target downrange. It doesn't have to be perfect but the closer the better. This gives you a much more accurate way to measure from the first shot horizontally and vertically. The 'plus' way is good if you are using a bipod or bag and rear bag or whatever. Just take a tape measure and a pen or marker with you while shooting.
Set up at 25 yards or whatever is suitable and fire one shot. [Note: a good rear bag or a led sled makes a huge difference.] The distance you are at needs to correlate to your caliber and load as it relates to your desired zero distance. Getting a rough idea of the ballistics before you start helps. You need to take into account scope height and all that when plugging the data in though.
95% of the time you are on the board somewhere after just one shot. Go to the board and physically measure from your aim point to your point of impact on an X Y axis. By that I mean how many inches left or right and how many inches up and down. Don't measure in a diagonal line. This is why it's important to make everything square before you start particularly if you are just using bags or whatever to rest your rifle. Mark the bullet hole with a pen or marker.
Do the math and extrapolate what that means at your desired zero distance. If it's 50 yards or 100 yards just calculate and adjust the scope accordingly. If you use a led sled or something like that you can just dial up or down and over just so long as you do not disturb the gun while doing so.
Go back to your desired zero distance and fire another shot but don't waste shots. At this point it might be a tad bit high or low but horizontally it should be fairly ok. Measure. Don't eyeball it. Make fine adjustments as needed after each shot.