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When a zero is not really a zero


Breacher

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Hmmm.......you aimed 6" above a deer's rectum

 

1) a 6+12+ inch drop at 250y suggests a light load in 22 Hornet.

2) a 24"+ wind drift suggests a likewise underpowered cartridge...and /or a right hoolie wind...40mph at least

3) but usually deer would be facing into such a wind,so it's impossible ....unless...

4) ...it's a totally different deer....maybe shot by someone else...or...

5) ..you are on a differnt planet

 

 

You should aim to replace your rifle asap....it's only good for bullsh**ing.

:-)

g

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Hmmm....... POA ...you aimed 6" above a deer's rectum

 

1) a 6+12+ inch drop at 250y suggests a light load in 22 Hornet.

2) a 24"+ wind drift suggests a likewise underpowered cartridge...and /or a right hoolie wind...40mph at least

3) but usually deer would be facing into such a wind,so it's impossible ....unless...

4) ...it's a totally different deer....maybe shot by someone else...or...

5) ..you are on a differnt planet

 

 

You should aim to replace your rifle asap....it's only good for bull shih**ing,not for deer shooting.

:-)

g

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Hmmm. Now over 40 posts disecting -with variable consistency-what a basic shooting term actually means.

I'm not advocating 'zero tolerance' on what quasi technical terms mean-if 'head' (a term correctly describing the end of a cartridfge case between the 'web' and the primer pocket) is a minor irritant,so be it-the term 'bullet' is much prefered-the only somewhat more serious risk is miscommunication when the meaning/referent of terms are not agreed. It happens,just a heads up,and bite that bullet!

 

I'm with Breacher,and would add very considerably to his list of 'authorities'-sometimes military advice makes small concessions for convenience (few recruits are skilled shooters).But the definiton given is sound.I've been reading very extensively on all kinds of shooting for over 60 years,and the overwhelming mening of "zero a rifle" is operationally,this means that the POA coincides with the POI. ASany trajectory drawing will exagerate,because the bullet's flight is an arcc,not a straight line,like the line of sight in effect-the bullet will actually intersect the horizontal at two places-one near the muzzle-say around 25 yards-as it ascends,and again at the "zero distance" when it descends through the horizontal-normally around 175-200y.The variation is due to physics,aand the MV etc etc of the bullet,and the powder charge etc etc. This trajectory conveniently means that most bullets will be about 1-1.5 inches high at 100y,and 'zero' at said 175-200y-so it is CONVENIENT to sight the rifle in (a useful distinction) to be 1,or 1.5 inches high at 100y (or indeed any other amount 'high' depending on the modal (most frequent)range expected for shots-it is a shorthand to say that such a rifle is 'zeroed at 100y" and is indeed an error-it is sighted in to be 1.5 inches high at 100y,so as to be zeroed at 200y (ie recross the line of sight,and POA coincides with POI. AT 100y POI will be 1.5 inches abouve POA.

 

Now several points have been raised,and some comments are in order.

Almost all the literature is primarily concerned with scope sights (but see below-iron can be a genuine exception).

The above definition is usually interpreted as the POI being the central aim point (usually cross hair in the scope)-but it need not be-any specified mark can be used,thoughgenerally centre is best (but see below) and assume unless otherwise specified (see below).

 

Most of the discussion points actually conform to the above,especially if 'hold off'/"sighted high at 100" etc are used-operationally,they work,and reduce to the stanfdard definition (despite some uncertain descriptions)...see below

 

OK,if we are on the same page-or agree to read our own page,which is fine until we read aloud and puzzle our audience (see below),then we can address other issues arising viz:

Mark has a good point wrt iron sights-'sitting' the target atop the correctly aligned irons is sometimes sensible-especially if the rifle is indeed sighted to shoot correspondingly high,aand therefore hit centrally. It can be easier to judge,allows better view of the whole target,and is 'good enough' when very fine accuracy is not required.Easier on old eyes,too.

(Mark,when you say "Iam two inches low" (off apost,was it-do you mean ""I aim two incehes low"...because shooting position/rifle hold etc can,for some-it isn't universal/PRS don't report it-can change POI. Sounds like an example of "holding off" really-but whatever works-pragmatics!

 

Zero can't simply refer to scope dials being on Zero- the rifle is 'zeroed' when POI=POA (or the shorthand approximation (I inch high at 100equivalent to POI=POA at 175y). It is sensible-feweer dialin in errors to then rest the dials to read zero,and indeed that is just what mechanical "Zero stop" facilities do,with the very useful added feature that just winding down until you can wind no more will return to your specified zero. None of this changes the 'zero' definition.

 

In rifle "zeroing" much mischief is avoided by remembering that the 'zero' refers to no deviation between the POI and POA at a specified distance,with a specified scope aim point (normall cenre cross/dot)...zero deviation-whre the bullet coming down on its curved trajectory cosses the horizontal. Any other useage is careless,and liable to misunderstanding -(unless it's made clear and explicit,and then may be only considered idiosyncratic.Don't mean it don't work;don't mean it do!!

 

I've mentioned centre aim point-but the definition holds using any aim mark-you'd be asking for trouble to use the fourth hash mark down,and second accross,but you could-slightly less cranky,I often sight one burris laserscope to be "on"at LR using the top mil dot

,when shooting -fast- at Fig 11s,and just holding differnt lesser distances with known lower mil dots.

You as shooter need to know what you are using,and need tobe clear if someone else that rifle/scope setting-inmy example,sayni it's zeroed at 500 is true,but withe unusual proviso that the top mil dot is the aiming mark.

Some posts correctly included horizontal coincidence of POI and POA-essential (and yet another reason to zero in 'no wind' if aat all possible. The wo dimensional trajectory curves can't capture the need for l/r coincidence-but of course,both turret knbs wll usually be needed.

 

It seems fairly obvious that the shooter shoud know the (true) zero- after all,it's not too problematic-an inch (!.5") at 100 is near enough true zero at 175 (200y).If there is any possibility of longer shots,then 6-9"low at 300 wilbe close,especially with a little finesse-the more potent loads nearer 6 inches.Hardly rocket science precision.

 

Talking of which-Litz spends some time on 'zeroing"-with the "standard" definition...once 'precision' is established with small groups,attention has to focus on accuracy-getting those small grous where you want them.'Zero" is clearly central-and needs incrasing care as distance increass-the '1.5 inch high at 100,so Point Blank Range" to 200 is adequate for such relatively short ranges,maybe a bit more, in a hunting context-fast shots,distance not exactly known. Long Rangers are faced with the more challenging task of perhaps a differnt zero-but sighters etc help,and vertical should not vary greatly-if it was ''on' at ( BR 1000y,it is unlikey to move...much-from last week...)

 

( Mark- here is some data on effect of a centered groupV 1/2 moa error in centering shots: 10 mph wind,+/- 1 mph wind error,=/- 1 y range error;.5 moa;10fps MVSD: 175 g 308w@2600fps: 600y:

centered// .5moa error %hits

 

10" target 99//82. 5 " target 74//28. (At 400y it's 100% except the off centre 5" target at 62%. 500y 100//96. And 93//39 %s)

 

-there is no such thing as 'can't' but it gets increasingly unlikely!

 

Good shooting,whatever words you choose ( as Alice's Red Queen rather controversially claimed-"

"When I use a word,it means what I mean,neither more nor less. I say what I mean ,and mean what I say.It's the same thing,you know". Alice was too confused to reply. (And shot off into another chapter,head spinning). ..........:-)

 

gbal

 

regarding words , in your case less would be so much more.

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I didnt state it was broadside on..

"Above its rectum" is a clue in my answer,but I didn't think that was done in the UK,and didn't want to be critical.

The ballistics and penetration don't really add up anyhow,though I suppose -on this mickey mouse level-a fawn is a deer...but surely..

"You can NOT be serious". (It's a Wimbledon thing,he won ,but wasn't asked to join the club.... but remained a fine player). :-)

g

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"Above its rectum" is a clue in my answer,but I didn't think that was done in the UK,and didn't want to be critical.

The ballistics and penetration don't really add up anyhow,though I suppose -on this mickey mouse level-a fawn is a deer...but surely..

"You can NOT be serious". (It's a Wimbledon thing,he won ,but wasn't asked to join the club.... but remained a fine player). :-)

g

you really are missing my point, regarding "aiming off", the distances quoted are irrelevant and were no way meant to be "factual", simply an example, where are you actually aiming? think of the centre of the crosshair as a reference point against your bullets actual position in space and time, and not actually where you are aiming. you obviously don't hunt live quarry, just poorly educated armchair hunters like myself.

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If someone has to aim that far off the deer's kill zone and above it, that would suggest that they're way too far out to be taking the shot in the first place :D

 

Deer sniping may be the fashion in the USA where we only ever get to hear about the 1000 yard kill shots on you-tube and seldom hear about the injured animals or misses. I'd like to think that we had more regard for our quarry here and the real skill is the stalk and not the pulling of the trigger (lets face it, anyone stalking who can't hit a deer in the kill zone at 150 yards shouldn't be stalking in the first place). Even blowing 20mph right to left, that's only about 6 inches of windage allowance at 200 yards and about a 4 inch drop for a rifle zeroed at 100 yds.

 

Some deviation from the subject though as this aiming off malarkey has nothing to do with the definition of what zero point is. It is what it is. If you're aiming off to get the shot to the intended target, of course you're not aiming at the bleeding target. You're aiming to hit the target given the conditions and range (assuming if we can for a minute, that we're not aiming over the top of a deer in line with it's arse hole). Deviation and pedantry?

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Just to give us something to think about with respect to authoritative, if unhelpfully niche, military definitions of 'zero':

 

The sight on my target-rifle is zeroed at 100yds - by which I mean that I have adjusted the sights so that the poi and the poa coincide at 100yds on a still day and then, importantly, i have set the wind and elevation scales to read zero.

 

The rifle itself isn't zeroed - just the sight.

 

When I lie down 1000yds from the target, I adjust the sight to that the poi will again coincide (more or less) with the poa. To do this I put on about 31' elevation, and whatever I reckon for the wind, Although I have adjusted my sights so that the poi and poa coincide once more, I can't imagine that anyone would describe my actions as 'zeroing' the rifle or sight.

 

I think we could all have saved a great deal of time if the OP had asked his guest simply how his sights were set.

A guest replying to the 'zero range' question based on the strict military definition might sound as though he has no idea what he's up to if his answer is (as mine would be) '180-200yds or so' - but that is just how MPBR sight-setting works.

 

I suppose the guest should have answered that he hadn't actually zeroed the rifle at all, and waited for his stalker to ask the right question? Mind you, he presumably had got a wind zero - just not an elevation zero. Discuss.

 

Or maybe not.

:)

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Yep

 

giphy.gif

Whilst I don't doubt gbals ballistic knowledge, his posts , for me anyway are impossible to make sense of . I have never known anyone use so many words to say so little !

 

Like you I don't even read them now, lol

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you really are missing my point, regarding "aiming off", the distances quoted are irrelevant and were no way meant to be "factual", simply an example, where are you actually aiming? think of the centre of the crosshair as a reference point against your bullets actual position in space and time, and not actually where you are aiming. you obviously don't hunt live quarry, just poorly educated armchair hunters like myself.

Lapua, I mostly thought it was an exagerated 'joke'-with a dig at 'complicated' explanations (point taken-shame the simple ones don't agree!) I've had over sixty years of 'hunting live quarry',read a bit,but mainly believe Litz these days! Oh,and 50 years in education.My tennis is 'armchair' as of this year.

 

Does it help getting on the same page if we think of shooting as applying a 'shooting solution' when faced with a target-I mean either Strelok/similar will give a read out of the appropriate clicks,based on input variables,or the shooter will 'hold off" to acieve the same result... eg if the shot is predicted(strelok) to be 3 inches low ,and one inch left....shooter either clicks in and holds dead on,or holds off by putting cross haairs 3 inches high and one inch right on target.Result should be same point of impact-it's success will depend on the 'accuracy' of the input data,including explicit/implicit zero data.

 

Can't say more,hope clear,and agreeable.(In both senses!) My tennis is 'armchair' at the moment-comfortable,but not the real thing!

Atb

gbal

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all rifles need to be zeroed at a specific range for any ballistic solutions to work. you need a datum point to work from.

Is this not a logical non sequitur?

 

You might easily have a datum point to work from without the rifle being zeroed according to the narrow technical military definition which some people seem to think appropriate to import into civilian life.

 

The datum point might be "1.75inches high at 100yds" - a datum point excluded from the definition of 'a zero' by the OP and others. The ballistic program doesn't mind your entering "1.75inches high at 100yds" rather than "poa=poi at 186yds" - it knows they're the same thing.

 

For my part, I am not serving with the armed forces: I understand the term 'zero' to relate to actually "setting sights to zero", but also to the activity of adjusting sights to some setting that I find useful for that combination of sight and rifle.

I use it as a description of the second activity because it also involves shooting and adjusting the sights accordingly, and the position to which they are adjusted becomes the standard setting for that scope/rifle combination. If I were to adjust away from that setting for wind or elevation, then I would after the shot 'return the sights to zero', even though the 'zero' might be 1.75" high at 100yds.

 

 

For every (complex) problem ,there is an answer that is simple,clear....and wrong.

 

Usually,more than one.

 

Good reading! :-)

 

gbal

I'm not sure that this is in fact such a (complex)* problem.

:)

* () pace tua, gbal

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the point is , the zero must be known or your data won't work , fancy word it as much as you like but it's a fact.

 

I've shot in comps against really clever people and not embarrassed my simple old self !

 

it's hits that count and taking this back to the first post , the target was missed.............

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Dalua

That is why it's in brackets-

 

The full,correct aphorism (or quip-as you wish) was:

 

"Explanations exist;they have existed for all time;there is always a well known solution to every human problem-neat,plausible....and wrong."

 

g

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the point is , the zero must be known or your data won't work , fancy word it as much as you like but it's a fact.

 

I think the point I made is that, according to the narrow military definition of the term 'zero' suggested by the OP and others, this is quite obviously not a fact.

 

I don't know the 'zero' (in the military sense) of my .270 - but I know it shoots 1.75" high at 100yds. The ballistic program seems to cope perfectly well with that.

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I think you are focusing too much on my mentioning the definition being used by military - I was not implying that it translates to civilian life.

 

But they ( and Police to some extent ) are among the few organisations who have comprehensive training courses on marksmanship.

 

So when looking for definitions of shooting terms, one is bound to be end up there.

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I think you are focusing too much on my mentioning the definition being used by military - I was not implying that it translates to civilian life.

 

But they ( and Police to some extent ) are among the few organisations who have comprehensive training courses on marksmanship.

 

So when looking for definitions of shooting terms, one is bound to be end up there.

Well, if we're allowed to deviate from the very narrow military/professional-marksman definition of a 'zero' which seems to be the basis of any disagreement on this thread, then there's nothing further to discuss.

 

'To zero' can then mean 'to set the sights; if not actually to zero then to some other setting the rifleman finds useful'', and the 'zero' can be used to mean the result of that setting quoted in terms of a known poi relative to poa at a convenient range.

 

Happy days!

 

As tackb points out, the target refered to in the OP was missed - but I, and probably others, have missed targets of that sort at 250yds (and maybe closer). Speaking for myself, when this has occurred it has had absolutely nothing to do with my not knowing where the poi and poa of my rifle coincide.

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