Zeroing at shorter range

[Pickles]

I'm by no means a ballistics expert so have probably overlooked something pretty obvious...
I have always zeroed at 100m and not had a problem, but recently I have been messing around with a ballistics calculator and found that all the calibres I shoot (excluding .22lr) put you give or take an inch high (25mm for those that don't like mixing metric and imperial ) when zeroing at 40m.
Is that the case or have I made an error entering data into the calculator? I guess my question is why not zero at 40m and have a bigger target picture and less margin for error?

 

[Rhodesianjess]

With a new scope, I take first shot at 35 yards. Shows gross errors,puts you somewhere near. Once on, I back up to 100 and fine tune.
Extra distance shows up any drift at shooting range for beasts, give or take. Extrapolated out to 200, shows up even more adjustments required. Short range handy for initial zeroing but need longer distance to confirm.

 

[Alantoo]

I guess it depends how confident you are with you and your rifle's shooting consistency, group size and mensuration. It is a lot easier to get somewhere close measuring subtleties over 25mm than 10mm...and even easier if you stretch out to shoot at 200m and are then measuring 50mm.

I would say there is a greater margin for miscalculation the closer you are...no reason that a 40m check for scope knock once zeroed wouldn't be okay though, anything is better than nothing.

The further out the better so that you can clearly read any error...I would think of it as an amplifier of any aberrations.

But if you are going to be shooting something at 300m it would be better to actually know where the bullet is going at 300m rather than calculating it from a 40m shot position.

Alan

 

[Rewulf]

Is that the case or have I made an error entering data into the calculator?

No , its do able , I actually zero at 75m , but can you really gauge accuracy at 40 m ?
If youre happy at that crack on .

My 75m zero makes me half inch high at 100m , mounted a little high at 2.5 inch, Im an inch and a half at 200m (.223)

 

[Sonicdmb73]

Well sort of. The FBI and other similar agencies have a short range target that they use to check their zero. Basically aim at X hit Y all’s good.
So in theory you can use your near zero to get your far zero correct. Assuming your bullet crosses the line of sight twice. Cartridge, scope height, bullet weight etc etc. All play a part in if and by how much.
However the way this method falls short is the error margin. Essentially the further away your target the easier it is to determine what your group size is and where the centre of said group is. Close up you’re dealing with fractions of an inch at say 150yds you might be looking at a 1/4”.

 

[Pickles]

Extra distance shows up any drift at shooting range for beasts, give or take. Extrapolated out to 200, shows up even more adjustments required

The further out the better so that you can clearly read any error...I would think of it as an amplifier of any aberrations

However the way this method falls short is the error margin. Essentially the further away your target the easier it is to determine what your group size is and where the centre of said group is. Close up you’re dealing with fractions of an inch at say 150yds you might be looking at a 1/4”.

Very good points. Consistent groups at 100m indicate a pretty good rifle/ammo/zero combination I guess. Will stick with the 100m zero!

 

[Heym SR20]

Its always useful to know zero at shorter range. It’s normally quite easy to find 25 or 50 yards where you can take a safe shot to check zero, even if you don’t have access to a clear 100 yards.

With most loads and calibres, a 50 yd zero pretty much gives an 1” and a bit high at 100, and then a smidge low at 200, but looking at a box of 243 100gn ammo, 0.3” low at 50 equals a zero at 100, whilst 0.3” high at 50 equals 1.5” high at 100. In other words a 50 yd zero is good enough for most stalking purposes, but if you are going to shoot much beyond 150 then you should check your shot at 100 and 200, as a small change can have a big effect downrange.

Once zeroed, If you have a shot saver then note down the coordinates. If you don’t find a A4 piece of paper, with a black dot. In your house or garden get it 10, or 20 yds away. Clamp your rifle firmly and bore sight it on the back dot - make sure its centre of target. Then get a family member to mark where the cross hairs align whilst you look through the scope. This gives you a quick check reference you can use in the future, especially if the rifle has taken a knock.

 

[308rws]

A couple of US links on the topic which may be of interest/use :

Different Zeros For Different Heros - Uncle Zo
ShootersCalculator.com | Point Blank Range Calculator

 

[Utectok]

Very good points. Consistent groups at 100m indicate a pretty good rifle/ammo/zero combination I guess. Will stick with the 100m zero!

I don’t quite agree pretty bad loads will zero and post good groups at 100m. If you really want to test your load check groups 350-400m and look for vertical spread. But tbh it only really matters if your stretching it a bit in the field.

 

[wully1234]

Mrd calculator, takes the guess work out of it ..

 

[enfieldspares]

When setting up a 'scope initially on a rifle I'll fire, if I can, the first shot a ten yards. Then adjust at that range until shot and 'scope align. Only then will I then go out to one hundred yards. Indeed ideally that first shot is best at just a mere six yards. Both my walking and my ammunition get saved that way.

 

[Sonicdmb73]

Mrd calculator, takes the guess work out of it ..

Not really, as unless you feed it accurate data in it will not be a 100% match to your trajectory.
Most MPR calculators don’t account for group size either.
Ballistic apps all require tuning to get accurate results. They might give you an idea of expected results. But only shooting at near, far and mid trajectory will confirm it.

 

[Foxyboy43]

Erm, so many ways, whatever happened to the one shot zero method?

 

[badbob]

Yes , bore sight, first shot 10 yards, then one shot zero at a 100 yards .
Shoot your groups on the range. . Talking of groups ,good groups are not a lot of use if they are not in the bull. We see a lot of photos of good groups off centre.

So you need to do a tall target test for your reticle elevation adjustment and a four shot walk around the target with eight clicks left, up ,right, and back down again.

Then the SD black dot of doom.

 

[Kevgun]

It's how I do my NV rifles, never had a problem further out, just remember with anything that involves a computer, Rubbish in, Rubbish out. all my Scoped rifle are zero dead on for 100 yards and dialled accordingly. For example with my NV though my .223 with a Drone x15 on is Zeroed for 60 yards second zero is 270 yards once zeroed dead on at 60 I confirm at 270 to check all is good, normally works for me, but emember scope height plays a big part in the 2 distances higher the Scope above the bore line, the further between the 2 zero's

 

[TomDeer]

I usually zero on a 100 yard range to start with and then see what the bullet is doing at 40 yards on the same range. With that information I have relative confidence checking zero on a 40 yard range from time to time. The reason for this being the properly set up 100 yard range is 35 miles away and the 40 yard one is 2 miles away.

Whilst I prefer doing it this way round, I have zeroed on the 40 yard range and then subsequently checked on the 100 yard range and found the results to be pretty much as per the manufacturer's ballistic data. Any variance between the two will usually be due to me and weather/wind rather than any significant issue with the ballistics data. I do however prefer the certainty of checking to know exactly what is happening on paper at 100 yards rather than relying on the data and assuming what it does at 40 yards it will do at 100 plus yards as it builds confidence.

Additionally, my ragged single hole groups at 40 yards are usually not single ragged holes at 100. Instead, at 100 yards, they might politely be described as "fit for purpose" and I don't think I can blame the rifle for that!