when to call a rifle "zero'd"

[z7]

I grew up with my father taking a deer rifle out once a season or so, firing 3-5 shots and as long as it was within a few inches it was "good enough"

I now am trying to get into a little more long range, precision stuff. so I got a really well made 308 win, SMK's and made up a good load. when do you call it "good enough" for a 100yd zero on a target gun?

attached is a picture from over the weekend. 5 shots each group. the group on the left i fired first, saw it favored the right side so I came .1 mil left. now the left side is favored. I need to come right about .05 mils (vortex razor gen II, you can adjust in between "clicks") and maybe .02 mils up.

group on the right, the lowest shot I pulled, so I am ignoring that one for center of group/zero. the stickers are 1"

 

[BrocLuno]

If that's a 100 yds, it prolly should be 1 1/2" above the center of the bull. That'd make it something like 1 1/2" low at 200 or so. So you'd be center mass at anything out to 250.

Or, you can put it dead on and use the Mil-Dots to adjust for range and windage ...

 

[Snyper]

A true "100 yard zero" would be when the crosshairs are centered on the bullseye at 100 yards, and the point of impact also hits the center of the target.

The term "zero" means the distance where point of aim and point of impact coincide.

 

[Slamfire]

A rifle is really and truly zero'd once you shoot it at the distance you plan to use it, with the loads you plan to use, in the shooting position it will be shot with, and establish the elevation and windage measurements which will put the bullet in the center of whatever you are aiming at. Zero's have to be established at the range not on a computer or some ballistic table.

I have been taking my hunting rifles down to CMP Talladega and shooting them on their wonderful electronic targets. It is a revelation to find where the first shot out of a cold bore lands. It is also a surprise to find that my carefully established 100 yard zeros are quite off at distance.

This rifle, while the elevation was reasonable for 300 yards, 4 1/2 MOA up from the 100 yard zero, being 2 1/2 minutes to the right, that was a surprise. Also, was the effect of a cracked case neck, which was my seventh shot. That shot went low. Shots due to cracked case necks do not always drop to 6 0'C, I have not detected any pattern to cracked case neck shots, other than that the bullet does not always go where it is aimed.


I have well established zero's with my Across the Course service rifles, my windage for the two hundred yard rapids is always different from the windage standing. Elevation is a little different. Zero's also change based on environmental conditions. I have noticed, the further I go out, that temperature differences make a difference on elevation. And zero's, for in cold weather, I am dressed in several layers of clothes and that effects something, for my cold weather zero's are always a little different from nice weather zero's.


I wish zero's were deterministic, for all we would have to do is look at some table, find the X,Y,Z value, and turn our elevation and windage knobs to compensate, but it does not work out that way.









By the way, good groups. Now, move the target out and see what happens.

 

[z7]

it is 100yds. I am looking for a 100yd zero as I will be either holding for wind/drop or most likely dialing.

this is mainly a target gun, I don't have a whole lot of opportunity to hunt given land access and time constraints.

last month I was shooting steel at 450yds with no wind and was getting good groups, 3" for 4 shots, I was really happy but alas, I am out of 178 Amax and with them being discontinued I have loaded up some 175 SMK's. that group is the 175 SMK "zero" group. it favors about .05 mils left and maybe a similar amount low on the 1" target. if you all were taking your rifle to a competition would you call this "Close enough" and then count on a few sighters before the comp starts to confirm? obviously conditions and positions change along with loads, I am just trying to get a feel for when guys reset their turrets and call it "good"

or is it never quite "good enough?"

 

[Bart B.]

In the beginning, "sighting in" at some distance was the common vernacular. Then it changed to "zeroing" for reasons unknown. Technically, it's having all shots cluster about the point the sight's at when the rifle's fired. Variations are going to occur based on ones perspectives and objectives.

 

[jmr40]

As a hunter I want all shots perfectly centered at the range where shots are most likely to be taken. With most modern centerfire rounds 100 yards is best most of the time. I also want to know where the shots impact the target in relation to point of aim at longer ranges, possibly closer ranges if the zero is 200 or 300 yards. I strongly disagree with the antiquated notion of zeroing so that bullets impact above point of aim at ranges where shots are likely. You just complicate things at the ranges where you are most likely to shoot without really helping at ranges where you will probably never take a shot.

If you anticipate 200 or 300 yards to be the closest shot you'll get then zero for that range. The bullets will impact 2-4" high at 100, but since you don't anticipate shots that close it isn't a problem. But virtually all shots are taken at 300 yards or less. All modern centerfire rounds zeroed at 100 yards make 300 yards shots possible with little or no hold over. Why complicate things for those much more common 50-100 yard shots by having bullets impacting above the point of aim at those ranges. Beyond 300 yards you need to be using range finders and scopes designed for long range shooting with either dots or dials.

In a hunting rifle group size is something we worry about too much. If the rifle/load/shooter is capable of keeping 3 shots inside 1" at 100 yards that is about all the accuracy you can use when firing from field positions at game. A rifle/load/shooter that will keep 5 shots inside 1/2" or less at 100 yards is nice to have, builds confidence, and is fun to show off, but won't be any more likely to hit a deer size animal in the field.

Now for a target shooter, shooting prone or from a rest, at known ranges, then having those groups in the .2-.3 MOA range for 5 shots is vital. if you want to win you'll be trying for groups in the .1's. But for a hunter, at ranges out to 400-500 yards a 1 MOA rifle is just as likely to hit a deer's vitals as a .3 MOA rifle. You're shooting at a much larger target.

 

[hq]

In my book there's a very simple definition: When any possible change to sight adjustments won't bring point of impact closer to the point of aim, it's zeroed.

 

[JRWhit]

In hunting rifles I prefer, to find the butter zone of the cartridge. That is the zero that provides a cross hair shot at the widest range of distances that are likely to be used when hunting. Example; On a white tail I have a grapefruit sized kill shot. If I aim dead center of the kill zone the bullet can hit approx 2-1/2" higher or lower and still be inside of the grapefruit sized target. That typically has me looking at a zero that will hit 2-1/5" high at 100 yds. That is based on my specific, likely ranges in play where I hunt. Depending on the rifle I use that puts me out to a 250-300 yd kill with a cross hair shot. That perfectly matches my specific hunting ground and leaves no need for elevation compensation and on a grapefruit sized target, it has to be extremely windy to have wind-age effected enough to miss at those distances.
Of course target work is much different but depending on what reticle you have, find the most beneficial alignments based on what target distances you will be firing. Even if the cross hair has only a thin wire that meets a thicker wire in the cross hair configuration, it will have a specific distance in relation to target based on scope power that can be used to judge elevation and range. The manufacturer of the scope will have it published usually in the manual.

 

[Bart B.]

Now for a target shooter, shooting prone or from a rest, at known ranges, then having those groups in the .2-.3 MOA range for 5 shots is vital.

Here's a dose of reality on group sizes shot from prone or a rest.

Benchrest aggregate records comprising several 5-shot groups at 100 yards have all groups about 3/10 MOA and smaller. All the rest are larger. At 300 yards, those aggregate records' groups are about 1/2 MOA and smaller.

Center fire rifles shot slung up in prone at those same ranges with 10 or 20 shots per target have record scores set with groups a little bigger than one MOA.

In hunting rifles I prefer, to find the butter zone of the cartridge.

Thats commonly called the "°point blank" range.

 

[Art Eatman]

I go along with Post #8. I've always sighted in my centerfire hunting rifles for two inches high at 100 yards, which generally is dead-on at 200. Then I go take a nap; nothing further is needed.

 

[Driftertank]

All my rifles are zeroed at 200yd. The reason being that anything bigger than a prairie dog will require virtually no mental gymnastics for a lethal shot at any range from 0-250yds. Just center crosshair and squeeze. The round will not hit more than 3" high or low anywhere in that range, and any shot taken at longer range than that will likely present more time to set up.
It also means, in the case of long range shooting rifles, less vertical correction at longer ranges.

And my experience is that either of the groups the OP posted would be "zeroed" for me, depending on conditions. When shooting long range, you will be amazed at what can effect the relationship between point of aim and point of impact. I have found that shooting at a different time of day can change my zero, simply because of the direction the light hits the target or enters the scope, to say nothing of wind direction. Chasing zero to .001" may become an exercise in frustration as conditions change.

 

[horsey300]

Whether firing 5 rounds at 100 yds or 20 rounds at 500 yds, when the center of the group is over the center of my aiming point, I'm zeroed. I don't care if I'm shooting targets or hunting, the distance I want to ZERO for will show poi centered over poa, that may or may not increase Max point blank range effectively, but the cross hairs will be dead center of the group at that distance. If there's too much wind, I don't zero that day because it increases the uncertainty of any adjustments I'd make in other conditions (no wind, wind in opposite directions etc).

 

[Llama Bob]

Several people have missed that he's zeroing a target rifle, not a hunting rifle. Maximum point blank range zeros are great and all (I use them myself) but they just complicated matters for target shooting where you'll be dialing your drop at all distances.

There's no reason not to make use of the sub-click adjustments on your scope. But I would do three things first:
1) Shoot a group with more shots
2) Shoot multiple groups with the same zero where you re-do the setup of your rifle (take it out of the case, get in position, ideally different lane etc.) each time. You may find that aspects of your setup cause the group to move.
3) Be 100% sure your air is dead calm. Even indoor 100y ranges have airflow patterns. Because I know my indoor range has a left-right wind and it varies depending on what the HVAC is doing, I set my drop at 100y but my windage at 25y. This matters only a little on centerfires, but it matters quite a bit on 100y rimfires.

Cold bore shots have to be investigated on any given rifle. If the rifle is free floated, everything is true, and the powder used is relatively temperature insensitive you will frequently find that the cold bore shot is in-group at whatever distance you're interested in. But for some other rifle configurations, they will have a behavior all their own. In disciplines where the cold bore shot can be a sighter, that may not matter. For other applications, you'll need to profile it (and possibly the 2nd and 3rd shot as well) as they will behave differently. I would also chrono cold-bore shots and make sure they're in-group velocity wise. I've never seen much difference myself, but some people swear the cold bore shot is more than 100 ft/s slow in certain rifles. The difference is probably that I avoid highly temperature sensitive powders like RL17, but it's still good to know for sure for your rifle & load.

I recommend never taking a shot that counts on a clean bore (as opposed to a cold bore which may be unavoidable) . This frequently means storing rifles dirty, which is an excellent practice contrary to what grandpa said.

 

[Bart B.]

I have found that shooting at a different time of day can change my zero, simply because of the direction the light hits the target or enters the scope,

I've never seen that happen. Nor do I understand why that would matter. Reflected light from the target travels to and through the sights (of any type) and into the aiming eye on the same path 24 hours a day as long as the atmosphere stays the same.

With a post front sight, however, the direction light strikes its sides can cause windage errors. And the size of the aiming irises on the rear sight and aiming eye will change with different amounts of ambient light causing elevation problems as the apparent size of the round black bullseye changes causing elevation problems. Hence, the old moniker "Light's up, sights up; light's down, sight down" that compensates for it.

I read an article some years ago about light rays traveling from target through sights and into aiming eyes. A scope sight was clamped into a fixed point on a bench at a rifle match. It was zeroed in the middle of a tiny target at some distant range so one could easily see any shift in target position relative to the reticle. People were asked to look through it at different times of the day as the light changed and mirage (heat waves) wrinkled across it different ways. Everyone said the scope reticle never changed its position relative to its aiming point all day long and into the night. Don't believe this? Conduct your own tests.

 

[horsey300]

In the beginning, "sighting in" at some distance was the common vernacular. Then it changed to "zeroing" for reasons unknown. Technically, it's having all shots cluster about the point the sight's at when the rifle's fired. Variations are going to occur based on ones perspectives and objectives.

I think the change occurred in a large part thanks to hunters for exactly the points illustrated in this thread, I've been handed rifles off hand and told "I sight in for 200'' then upon taking a shot or two, find that they were "minute of dead" at 200 and upon my question "exactly WHERE did you ZERO" the reply is, "I can hit a coffee can/milk jug/etc at 200 yds!" Followed immediately by my response, "can you poke a hole in the 'o' of Folgers?" Rarely is that a yes......I think zero became more accepted to avoid miscommunication confusing the mpbr with a true zero sight in. I don't target shoot competitively but deer dead at 200 rarely allows a head shot on a prairie dog at quite various distances. Indeed, one kid I met last fall thought his rifle was sighted in after only one shot at 100 yds and hitting 7" low of the bull's-eye, I feel "zero" imparts a sense of precision expected to be greater than the avg Joe's good enough sight in. For the purposes of targets (competitive or otherwise as noted by the op) mpbr sight ins are not good enough.

 

[BrocLuno]

The biggest issue for me is not high or something at 100. It's cold barrel first shot issues. I have three rifles that will throw the first round out of clean cold barrel high about 2" and left about an inch. So I have to set mine up to shoot right a bit.

Personally I set most of mine at 1" high and 1" right at 100 because I'm in my medicare years and I won't shoot anything but the 22-250 beyond 150 at an animal. And with the settings explained above I'll get into that grapefruit on the first cold shot, or the follow-up. And that's what I have to do.

The 22-250 will pretty much bug hole from cold to 10th round. So that one is "zero'd" at 200 and good to 300. But it's a bull barrel, and I'm not hiking it all around. It's off the hood of the Bronco on my pack or a blanket or something.

Each rifle is different. And each is worked to be close to point of aim under most conditions. Wind will have to be doped at the time and corrected for, same as slope ...

 

[illinoisburt]

I believe the op is seeing the limitation of the adjustments on the scope. 1 mrad is about 3.6 inches at 100 yards so a 0.1 mrad click is about 3/8" of travel. That is about how far the center of the group appears to have moved. So unless he is going to adjust the mount ever so slightly, the dead center location is currently between clicks. So the question becomes are you happy with being 1/8" to 1/4" off to one side or the other of centerline.

 

[Llama Bob]

I believe the op is seeing the limitation of the adjustments on the scope. 1 mrad is about 3.6 inches at 100 yards so a 0.1 mrad click is about 3/8" of travel. That is about how far the center of the group appears to have moved. So unless he is going to adjust the mount ever so slightly, the dead center location is currently between clicks. So the question becomes are you happy with being 1/8" to 1/4" off to one side or the other of centerline.

The scope he's using (a Vortex Razor HD II) has sub-click adjustment capability.

 

[mavracer]

It depends on the rifle and scope and what I want to do with it, for guns with mil dots and target dials zero at 100 means just that crosshairs perfectly centered and bullet holes perfectly centered, however for a hunting rifle I'm more apt to use "point blank range" where I'm a inch or 3 high at 100 yards depending on cartridge.

 

[Sunray]

"...with them being discontinued..." Did you tell Hornady? .30 cal 178 grain A-Maxes are still on their site.
Anyway, like Snyper says, you're zeroed when the POA matches the POI. However, you need to know where a particular load hits at assorted distances for hunting. Not so critical for fixed distance target shooting, but you need to know how many clicks is required to change distances. At 100, a .308 will be on target out to roughly 300 yards with a 3.5" high zero.
"...different time of day can change my zero..." Nope. That's your eyes.

 

[JackSprat]

My Dad always lined his up just a hair to the left,even his 22s because he thought he pulled to the right a little in an actual hunting position..I always line mine up dead center at 100 yard instead of the 2" high method that is more common around here,.I have pulled a few pretty long shots in my day,but I just aim a little higher.

 

[illinoisburt]

The scope he's using (a Vortex Razor HD II) has sub-click adjustment capability.

Kind of the point I was trying to make. He is between clicks. So would another person be happy with that, or should he finesse to get that last 1/8" of movement?

 

[RPRNY]

when do you call it "good enough" for a 100yd zero on a target gun?

attached is a picture from over the weekend. "View attachment 228312

That's zeroed ! Nice shooting.

 

[Trent]

Kind of the point I was trying to make. He is between clicks. So would another person be happy with that, or should he finesse to get that last 1/8" of movement?

If you are between clicks, there's not an awful lot you can do about it. This shows up at longer distances even more acutely. When I shot f-class a single "click" could send me from grouping along one edge of the X ring to the other side of the x-ring on a 1/10 mil adjustment. (One "click" on a 1/10 MIL scope at 600 yards is 2.16" and the X-ring is 3")