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Two separate issues I’ll comment on:
Lostintheozone is spot on. With a bolt action you can remove the bolt and then sight on a small bullseye target at 25-50 yards. Just make sure the bull is centered in the open end of the muzzle and that you have equal amount of bore visible all the way around the open end of the barrel. With the rifle supported so it won’t move, adjust the reticle to center on the bullseye. You may have to go back and forth and rinse and repeat a few times as a little moment often happens with large adjustments.
Once it looks good take a shot. It’ll probably be a few inches low, but should be on the paper and pretty well centered in windage.
Now, hold the rifle very steady on the front rest and rear bag so that the cross hair rests on the center of the bullseye. Then without disturbing the rifle, adjust the cross hairs so that they move over to the hole in the target. You are just moving the point of aim to the actual point of impact.
Take another shot. It should be very close to center of bullseye. Make a click or two of adjustment if needed.
Then fire a 3-5 shot group to confirm the short “zero” , but then confirm it at the actual long range “zero.
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If you have a ballistic app and have a pretty good idea of your actual velocity, you can go ahead and adjust the elevation to zero the rifle at what ever short range you have available.
But the ballistics and the sight height matter.
For example, I have a scoped Mini 14 and feed it Hornady 55 gr FMJBT bullets loaded to 3000 fps. The distance from the center of the bore to the center of the Luepold 2-7x33 scope is 1.7”.
The Creedmoor reticle in the scope is designed for a 100 yard zero, with two 1 MOA dots that are 2.2 MOA and 4.8 MOA, with a picket 8 MOA below the reticle. That then works out to a 100 yard zero and hold points at the dots for 225 yards and 325 yards, as well as 400 yards at the pointy end of the picket. It’s not a bad setup for a 1.5 MOA accurate mini 14, it’s easy to remember the ranges for the dots and picket, and it’s easy to extrapolate between the dots and picket.
To get a 100 yard zero with that sight height and load, it will be .9” low at 25 yards and .3” low at 50 yards, and I can do that if I am at an indoor range and don’t have access to a 100 yard range - but I would want to use as long a range as possible, and be very precise with the zero - shooting tiny groups, knowing exactly where the center of the group is, and adjusting the scope so the group is centered exactly where I need it to be at 25 or 50 yards.
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Similarly, I have another Mini 14 with iron sights and a sight height of 1.2”. Since the sights are not readily adjustable, I zero it for 275 yards. That gives me a +/-5” point blank range of 325 yards. In other words, the maximum mid range trajectory is +5” (and happens at 150 yards, while it is 5” low at 325 yards. That lets me hold dead on out to 325 yards and keep the point of impact 5” or less from the point of aim. A 400 yard shot is 18” low, or basically hold top of the head on an IPSC head and torso plate).
But given the lower sight height, it’s 0.5” high at 25 yards, 2.0” high at 50 yards and 4.1” high at 100 yards.
That 4.1” high at 100 yards is handy as I can take a 100 yard small bore target with its 8” diameter bullseye and use a 6 o’clock hold. With the thinnest possible gap between front sight snd bullseye that 4.1” high should result in a group centered in the 10 ring.
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100 yards out is also far enough down range to give me a high degree of confidence in the 275 yard zero. A 25 or 50 yard zero does not, as even a 1/8” error at 25 yards will result in the 275 yard zero being 1 3/8” off at 275 yards. A 1/4” error at 25 yards results in a 2 3/4” error at 275 yards.
In short, the distance you choose for a zero will depend on:
- the ballistics of your actual velocity and the BC of the bullet;
- the sight height of your rifle and sight;
- the reticle in your scope; and
- your intended use.
You have to consider all of it as a system.
