When a zero is not really a zero

[Dalua]

 

Its just that zero is something else. Its poi and poa alligned when elevation and windage settings are at zero. The hint is in the word ZERO.

 

A shooter might have a rifle which when sights set at 200 shoots 2" high and 2" right. Just because he knows this and aims 2"low and 2" left does not mean his rifle is zeroed !

 

I would argue differently: that the fact that the sights are set at zero means that the sight/rifle combination is zeroed - and that's an end of it.

The word 'zero' refers IMO to a setting on the scale of the sights. My rifle as described is esentially 'zeroed' anywhere between 0 and 200yds for stalking purposes.

 

In fact, of course, there are no numbers on my S&B 6x42 - so really the sight cannot be 'zeroed', other than within the meaning of setting it so that I can shoot to 200yds making zero allowance for elevation.

 

Perhaps we shoud described the activity of 'zeroing' rather as 'the setting of sights'?

 

 

[Dalua]

From a previous post.......

 

"I've no idea where the POI and the POA coincide - probably about 200yds - but that doesn't really matter too much"

 

This is just the point ! If you do not know the precise range poi and poa coincide, how can you say your rifle is zeroed ?

 

Zero means poi and poa coinciding at a known range. The rifle can then be said to be zeroed at THAT range. Shooting high at 100 yards is not a zero !

 

OK already - so my rifle is not zeroed according to your definition - or rather, it is, but I don't know at what range. However, that doesn't matter

 

By your definition, I should say 'my sight is set to shoot 1.75" high at 100yds'. The only way I could find out where the POI and POA coincide is to shoot from unauthorised positions on the range I use - it's probably 180-190yds or so.

 

As things are, I know where it shoots at 100, 200 and 300yds and will probably continue to use the adjective 'zeroed' for a rifle and its sights when I know the relationship between the POA and the POI is what I want it to be.

[Breacher]

I would argue differently: that the fact that the sights are set at zero means that the sight/rifle combination is zeroed - and that's an end of it.

The word 'zero' refers IMO to a setting on the scale of the sights. My rifle as described is esentially 'zeroed' anywhere between 0 and 200yds for stalking purposes.

 

In fact, of course, there are no numbers on my S&B 6x42 - so really the sight cannot be 'zeroed', other than within the meaning of setting it so that I can shoot to 200yds making zero allowance for elevation.

 

Perhaps we shoud described the activity of 'zeroing' rather as 'the setting of sights'?

 

The common definition of "zeroing" is poi and poa coinciding at a known range/s. It will do this at two ranges. This is when the sights are set for the known range and ZERO elevation or windage is needed. The rifle is then ZEROED for THAT range.

 

For example - my rifle is zeroed at 200 yards. So I say its zeroed at 200 yards. I dont say its zeroed a few feet low at 600 yards !

 

The clue is in the word ZERO.

[bradders]

 

Zero means poi and poa coinciding at a known range. The rifle can then be said to be zeroed at THAT range. Shooting high at 100 yards is not a zero !

 

No

 

If you set your turrets to zero with the bullet striking a known and chosen distance from what you perceive to be mechanical and visual zero, then that is still zeroed

My zero for 1000yds is 33Mins plus 2 mildots up

Because I'm out of elevation at that point and holding over, does that mean I don't have a zero even though I do?

 

Zeros can be whatever you want them to be, but a better term is "sighting in"

[Grum87]

The common definition of "zeroing" is poi and poa coinciding at a known range/s. It will do this at two ranges. This is when the sights are set for the known range and ZERO elevation or windage is needed. The rifle is then ZEROED for THAT range.

 

For example - my rifle is zeroed at 200 yards. So I say its zeroed at 200 yards. I dont say its zeroed a few feet low at 600 yards !

 

The clue is in the word ZERO.

But his turrets don't have a 0!!

[Dalua]

The common definition of "zeroing" is poi and poa coinciding at a known range/s. It will do this at two ranges. This is when the sights are set for the known range and ZERO elevation or windage is needed. The rifle is then ZEROED for THAT range.

 

For example - my rifle is zeroed at 200 yards. So I say its zeroed at 200 yards. I dont say its zeroed a few feet low at 600 yards !

 

The clue is in the word ZERO.

However, the 'zero' is the elevation and wind setting of your sights. You might well have 'zeroed' at 200yds, or you might have done it by shooting at 100yds and setting your zero a little high - but as you've pointed out, set at 'zero', the rifle shoots a few feet low at 600yds - with is therefore also equally truly the result of your 'zero' setting - so you could use the POI relative to the POA at any range to describe the results of your zero setting.

 

I think that 'zero' can be simply a numerical setting of the sights, or perhaps a range at which you may shoot with 'zero' elevation; as well as the act of setting sights.

 

As I've pointed out, in the traditional sense my scope is unzeroable, as there's no numerical scale at all. It doesn't need one, though - you just set it, put the caps on and go stalking.

 

Which leaves us with the idea that 'zeroing' means, without prejudice, 'the setting of a sight, or the act of setting it'.

 

Just my view, of course.

 

As far as 'bullet h**d' goes: it is simply wrong.

[Dalua]

Zeros can be whatever you want them to be, but a better term is "sighting in"

As ever, the calm and rational voice of reason.

[MrCetrizine]

Because of my own natural cant, the POA and POI on my ISSF rifle only coincide, if you're me. My rifle is zeroed for 50m if you're me but anyone else would be way off.

 

It's Schroedinger's rifle, it's both zeroed and not zeroed at the same time and the only way to be sure is to open the box... of Tenex.

[bradders]

As ever, the calm and rational voice of reason.

 

Yep, that's me alright

[Breacher]

No

 

If you set your turrets to zero with the bullet striking a known and chosen distance from what you perceive to be mechanical and visual zero, then that is still zeroed

My zero for 1000yds is 33Mins plus 2 mildots up

Because I'm out of elevation at that point and holding over, does that mean I don't have a zero even though I do?

 

Zeros can be whatever you want them to be, but a better term is "sighting in"

Wrong. Your rifle is ZEROED at whatever range zero elevation is applied. What you call your "zero" for 1000 yards is your ELEVATION for 1000 yards.

[Breacher]

But his turrets don't have a 0!!

Same same. Poi and poa coinciding without any elevation or windage applied - be it via turret or hold over.

[Breacher]

I think point blank and zero are being confused here too.

 

Point blank range is the longest and shortest range the bullet will strike somewhere on a certain size of target when aiming at the centre.

 

Zero range is the range it will strike the centre of the target.

[Grum87]

Same same. Poi and poa coinciding without and elevation or windage applied - be it via turret or hold over.

 

I'm taking the p!ss, personally I'm with you on this. But then again, my turrets do have 0's

[VarmLR]

There seems to be variations on pedantry going round in circles here

 

The term "Zero", or "to Zero" a rifle is really a very simple concept. It is to set the sights in a rifle, irrespective of what sights you use, so that at a known reference point, usually the "zero settings" on a scope, in still conditions, that a rifle is shooting with accuracy exactly where you want the POI to be at a known distance. For many, this will mean POA and POI being the exact same, a known benchmark. Typically, as George has pointed out, with factory rounds, when one knows one's 100 yard zero, a twiddle of the sights to 1.5moa up gives a MPBR that allows shooting to about 220 yards on deer without needing to make any further adjustments. Others will choose to zero their sights for a POI which allows the centre or mean of a group (which must really be statistically relevant so better not the usual 3 shot group and preferably a 10 shot group) to be precisely 1 inch above POA. Each can be a perfectly valid description of a zero'd rifle since by definition, the shooter knows implicitly for that distance what the POI is.

 

However, joining sides to be a pedant for a moment, one must also know when POI and POA coincide in order to accurately set the sights if dialling for ranges beyond MPBR. That's a pretty good argument for being able to accurately determine POI at further ranges.

[Breacher]

Well, a quick look at training manual pdfs from USMC scout sniper school, US Army and British Army all seem to agree on a definition of "zero".

 

All three have the same definition - adjusting sights so poi and poa are coinciding at a known range.

[MrCetrizine]

Point of aim doesn't have to be the centre of the crosshair though.

[Dalua]

Well, a quick look at training manual pdfs from USMC scout sniper school, US Army and British Army all seem to agree on a definition of "zero".

 

All three have the same definition - adjusting sights so poi and poa are coinciding at a known range.

I think the HO Guide uses a similar definition. Fortunately, it doesn't specify the degree of precision to which the zero range needs to be known

 

So I can confidently say that the the sight on my stalking-rifle is zeroed (although there is no 0) at 180-190yds. However, I know that when so zeroed, it shoots 1.75" high at 100yds, and about 8" low at 300yds.

[Breacher]

Point of aim doesn't have to be the centre of the crosshair though.

Regardless - with the PBR method being used, wherever your poa is, your poi is x number of inches high etc

 

And forget about scopes for a min - the same principles are applied to iron sight zero. Poi and poa coinciding at a given range which is said to be the range the firearm is zeroed for.

[Dalua]

Regardless - with the PBR method being used, wherever your poa is, your poi is x number of inches high etc

Not at the zero range it isn't.

[Breacher]

Not at the zero range it isn't.

Eh ?

[bradders]

Point of aim doesn't have to be the centre of the crosshair though.

 

Exactly

 

[Breacher]

Well, I will stick with the definition used by USMC scout sniper school, US Army instructors and our own British Army Skill at Arms instructors - a weapon is zeroed at a given distance when poi and poa coincide at that distance.

 

But I am happy to concede its pedantry of the highest order.

 

Now, dont get me started on those who say "could of" instead of "could have"...................

[VarmLR]

I think that there may be a few gentle chains being pulled Breacher. I don't think that anyone is really arguing against POI/POA coincidence at a set distance being the precision shooter's (correct) definition of "Zero".

 

MPBR is just that....it's not a "zero", it's a definition of a trajectory distance within the bounds of acceptable deviation from POA to POI which keeps a projectile within a specific zone. By definition, that cannot be a zero, just a sight setting for a specific purpose. For a CF sporting rifle, you may set the sites 1 inch high at 100 yards but zero is probably between 170 and 190 yards.

 

You may use iron sites with the aim point being target circle balanced atop rear site but you use the exact same aim point for all other distances when altering the sites to compensate, so one can still argue that it is a zero irrespective of what aim point you choose, because you know that the centre of the bull is the POI with the target inner circle balanced. That's seldom, in my view anyway, the best way to set open sites for hunting. I always used to set mine (when I still used open sites) with the aim point central to Bradder's site image 2 example.

[FGYT]

I zero at 88yrds as this is the highest point in the trajectory for my set up and coincidently is the distance I can shoot in my garden. Rifle is zeroed to this and turrets are slipped to zero I can then dial up to any range to shoot or check zero. For general stalking it's set to 2" high at 88yrds for a point blank range manly dialed precisely when long range and time allow if needed.

[gbal]

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