Home Forums Hunting & Shooting Ask The Gunwriters Where to zero

In looking at and playing with my ballistic program and running different loads and checking trajectory charts I'm wondering why use 100 Yd. Zero? I can see if your using turrets then standardization would maybe help understand the system but some of my scopes have turrets and some don't and whith the ones that don't it seems when hitting a given kill zone diameter would be easier with a 200 Yd. Zero. What am I missing? New to the mystery of ballistic science but trying hard to understand

For that kind of sight in it's not necessarily 200 yards you want.

Pick a vertical envelope you want to contain your trajectory, and your sight in distance will follow from that.

I'm not a gunwriter, but I'll throw my thoughts out. If 100 yards is the closest shot you anticipate and 300+ is considered normal then a 200 or even 300 yard zero makes sense. But if 50-150 yard shots are the norm and 300-400 is the max you anticipate (or have the skills for) then 100 yards makes more sense. Having the bullet impact 2-4" high at 100 yards causes more problems at short range than it helps at 300 yards.

With any of my rifles a 100 yard zero means the bullet is never more than 1/2" above or below my crosshairs from 50 yards to about 130 yards and is still only 9"-10" low at 300 yards. A 200 yard zero is still 6"-8" low at 300, but more than 3" high at some point. If I can compensate for 6" of drop at 300 yards I can figure out 9". In fact I can still make hits on deer while holding on hair with either zero. Once you get to 400 yards you have to start holding high or use some type of scope with dots or dials anyway.

At closer ranges, especially if shooting through brush having the bullet within 1/2" of the crosshairs makes it so much easier to shoot through small openings. A bullet 3-4" high may hit unseen brush and be deflected and it is just not natural to have to remember to hold low to prevent this.

A 100 yard zero would be fine in the woods, but could leave you short if you get a longer shot. The old "3 inches high at 100" rule is okay in open country, but might help you miss at shorter ranges as people seem to hold a bit high when shooting at game. 200 yards is a good compromise setting for most rounds, but as mathman said, you should try for a usable trajectory over as long a distance as is practical. Personally, I stay at 2" high or under at 100, which puts me on at 200 or so with the standard rounds I hunt with, and doesn't make it too tough to thread one through the bushes up close. I haven't had a shot at over 150 yards since the '80s, so it works for me.

Some folks with dials like to zero at 100 and then twiddle for the exact range, but I prefer simple.

Even when using turrets, many hunters sight-in at 100 then when before heading into the field they crank the elevation knob to 200 or 250. Most of the time there really isn't any need to dial to, say, 167 yards. Instead, out to 250-300 they just use the scope like a "regular" hunter would, by aiming at the middle of a deer's chest and not worrying about a couple inches of bullet rise or drop above the point of aim.

Some shooters prefer a distance allowing less variation from the line-of-aim. A good example is ground squirrle prairie dog shooting. I generally sight-in my rodent rifles an inch high at 100, even if I'm going to dial way out there. Depending on the cartridge, this will allow holding in the middle of a squirrel or PD out to 200-275 yards, without dicking with a rangefinder or the turret. The turret gets turned only at longer ranges where it's really needed.

Most big game rifles can stand to be sighted 2" high at 100 yards, though you might want to run the trajectory through a program to see what the highest point of the bullet is at, say, 150-175 yards. With a high-mounted scope and a really fast round the 15--175 yard height of the trajectory can be close to 3", which might be a little much for your purposes.

Back in the days before lasers and turrets became common, many open-country hunters sighted-in 3" high at 100 yards, and some still do. This sometimes results in a trajectory 4" or so high at 200 yards, but hunters who grow accustomed to this system often use it well.

I use the last scenario John outlined in that I really like to sight in 2.75-3in high at 100 yards paying special attention to how high it's going to be at it's highest trajectory usually 150-180yards. I really don't like the bullet being more than 3.5-4in high at the midrange. This allows me to hold on the backline of a whitetail out to 350-375yds and still get a lethal hit. This is w/a bullet in the 2850-3100fps range which most whitetail or elk rifles will do. powdr

If Varmint Rifle 1 to 1.5 inch's at 100 yards , Big Game 2.5 or 3 inch's at 100 yards

I've never found it a bad thing for the bullet to hit the target where X and Y intersect.

Without dialing, Ive always used 3" high at 100. With a CDS, 200 yd zero works for me, as I can deal with 2" high at 100.

This is really a very difficult question for me to address because we are apparently addressing a vast number of different calibers and other elements of ballistics.

However, to bring it back into conformity generally, addressing big game only, in the USA, exclusively, and setting the caliber specific adequate parameters, you will want to evaluate the caliber of rifle, velocity, bullet weight, powder charge, distance. Further up hill /down hill shooting/ distance/ wind direction/wind velocity. On average the general calibers popular which number in the thousands show that due to diminished velocity and wind direction are so influential past 300 yards that it becomes a luck of the draw, cross your fingers, and say a prayer.

I'm absolutely not dissing the long range shooters in any way and particularly Military snipers, a special breed with special equipment and extra-ordinary talent.

I zero at 200 yards and never shoot past 300 yards.

I do it the same way, varmint rifles 1 in. high, big game rifles 2 in high at 100.

I try to keep my all-around hunting loads in a 7" circle to 300 yds with a single aim point. More than worrying about the specific zero yardage, I worry about the impact point at 300 when I'm finalizing for a hunt. 2.5-3.5" low at 300 depending on the bullet/velocity. I shoot for the forward ribs and below the half-way up line on the body. Even on meat deer, the heart/lungs is a big area to hit. My zero ends up being somewhere around 250, and around 2.5" high at 100yds.

If I hunted with a flat-shooting magnum, 300+ yards would make more sense. If I had a CDS, or a BDC reticle, that would make a difference too: I'd likely set the primary POA at 200. I aim small, but I don't aim for small vital areas, even when I happen upon a close-range shot. It's just not how I set up and use my equipment.

If you are using turrets and dialing then save yourself a bunch of heartache and zero for 100 yards and set the turret at "0". Lots of reasons for that and it's easy to spin the turret for 200 or 250 yards and carry it like that if you want.


For scopes without resettable turrets and that have a BDC reticle the best way to use them is to zero at 400 or 500 yards using the appropriate stadia line in no wind conditions, which will absorb any errors in trajectory at long range where it matters and any at close range will be small.

For scope without resettable turrets or a BDC, zero at whatever makes sense. Remember though, that unless you actually shoot at 250 yards or whatever and make POA/PII you don't have a 250 yard zero, you have a ______ inches high at 100 yards zero.


As well if you use a MPBR "zero", that is to the center of your group, not the top or bottom. I've yet to meet anyone that accounts for that....

Mostly, what John M-D says. My only deviation is, I prefer sighting my varminters so the bottom of the group touches the aim point.

DD,

Here's a Western open country trick:

In a .270 Winchester with a 130gr bullet, 2" high at 100 will also put you 2" high at 200, and dead around 250. You are good to 325 while still holding on the hair.

If you think you will need to shoot further, it might be a good time to start thinking about some dials.

As others have mentioned, it all depends on your load, your sights, location, and your intended purpose. The vast number of combinations is likely why you're using a ballistic program in hopes of narrowing things down to a few ideas you can test at the range.

I'm going to focus on hunting where you're moving around the terrain, where the range to the target and time to engage the target are unknown. Also you're shooting from a standing position, and I'm assuming a good marksman with a good rifle and ammo can shoot 1.5 MOA groups. Yep, you need to consider group size, particularly at longer ranges.

I'm using a .308 win with Hornady's Superformance SST load that centers at 2840 fps, but like all ammo there's shot to shot variation, not only in velocity but the BC of the bullet. I'm allowing for +/- 30 fps for velocity and +/- 5% for BC. Also, the temperature, altitude, barometric pressure and wind change over time and as you move through the terrain. In this scenario you don't have time to dial-in the shot, so what's the best range to zero at?

I've set all the worst case values in one trace: low velocity, low BC, low temperature, high pressure, and 14 mph wind from 10:30, which gives a 10 mph head wind and a 9.9 mph cross wind. I've set the normal expected values in a second trace and the best case values into a third trace with a 14 mph wind from 4:30 o'clock, which gives a 10 mph tail wind and a 9.9 mph cross wind. Obviously, you can pick other values.

Here's what that looks like with a 100 yard zero.



Red is the worst case and blue is the best case with green being normal. The 1.5 MOA group size is displayed on the target. The lines are the path of the bullet from the muzzle (starting in the center 1.5 inches below the X and out to 1000 yards or out of view. See how the bullet paths rise just a 1/10 inch or so above the line of sight and given they start off 1.5 inches below due to sight height there's no good reason to zero this load at 100 yards. Also, windage and group size mean that shots can hit nearly 1.5 inches on either side of the X.

A good rule of thumb is to be able to keep your shots on a dinner plate size target, so what's the longest range where all the shots will fit within a 10 inch diameter circle. It's easy to move the sliders and watch what happens.



It looks like 205 yards is the longest zero for this load and these variations of conditions and group size. Given it's windage that limits the range in this case, you can shoot at any range from the muzzle to 205 yards with high confidence you're shot will be within 5 inches of your aim point.

Of course most ballistic programs only consider elevation when calculating maximum range, which works out to 291 yards, but here's what that looks like when windage and group size are added.



Using a 10 inch target you can see shots can be more than 9 inches below and to the right of the X at that range. The more real world conditions your ballistic program considers the greater its usefulness.

The best sighting in system is the one you shoot a lot with at various distances under various conditions. All the balisijectory systems in the world don't make up for shooting, shooting and more shooting.

Zero in the center of the bulls eye. That usually works for me...


Sorry if this was meant to be a rhetorical question...

Mac:

You wrote, "Also you're shooting from a standing position, and I'm assuming a good marksman with a good rifle and ammo can shoot 1.5 MOA groups."

If you meant that how it reads, if you can shoot 1.5 MOA groups standing, you can win the national championship and set the all-time record. I doubt that many hunters can put 50% of their shots into 6 MOA from the standing position.

There is no one answer to the OP's question. It depends on trajectory and game. Also the game does not always stand around while you use your rangefinder and turrets. A flatter trajectory lets you shoot quicker and hit better. For big game, I use a .300 Weatherby with 180 grain bullets. 3" high at 100, 3" high at 200, and right on or a bit low at 300. For 400, I don't shoot. A 270 with 130 grain bullets should be similar.

I estimate range (approximately) by comparing the animal's chest height with the distance from the center of the cross hairs to the part where it gets wider, with the scope set at 4X. I believe that Mule Deer wrote an article about this in a fairly recent issue of "Guns."

Indy -

I 'seldom' get to use my range finder BEFORE a shot. The vast majority of the time, I range AFTER the shot from the deer OR where the deer was BACK to where I was.

I learned of the 3" hi at 100, 4" hi at 200, & +/- zero at 300 from John Wooters back in the early 80s. When you use it for a while it becomes second nature. Out to 300 + all you need to do is hold center of the side of a deer.
At 400 yds you can hold on the back line and the bullet will drop in the vitals. (when the deer is standing)

And you are correct the 270 Win with 130 @ 3100 fps will be very close to the same.

There are others here on the fire who use this system too. It's one of the most simple for MPBR. It only takes some practice to develop confidence.