Optimum Zero Distance (How to?)

I just put the data in Chairgun and in the toolbox hit optimum zero

35 yd zero gives me a holdover for everything beyond 35, which makes it pretty simple.

50 yd zero makes it easier for targets 50+ yards, but requires hold under from 20 to 45 yards, with the most being 30-35 yards. If a lot of your shooting is between 20 and 40, factoring the hold under can be irritating.

Another way is to choose the zero distance you use the most, then dial (if you have target turrets) the other zero if you find you're shooting at that distance more that day or at that location.

Or just used to your holds and the more shooting you do that way the better you get at it.

My main gun is zeroed at 10 and 50 yards - with a max hold under of .9 hash marks at 20-30 yards, and 100 yards is 2 hash marks and one line thickness hold over. Not exactly rocket science but sufficient for my hunting needs. I printed out a small graphic and taped it to the gun for quick reference in the field.

Method:
​Post targets at
10, 15, 20,
30, 40, 50,
60, 70, 80,
90, 100 yards. Shoot 5 shots at a known POA (bullseye to 70 yards, there after added a single hash mark to pre-elevate the gun). With the FFP scope and a spotting scope - it was pretty simple to work it out.

Hawke optics has a great app / program: Hawke X-Act, they also have a more in depth program as well that gives you total control and input of values, but X-Act fits my needs well and is quick and easy to use. You choose from the presets for pellet weights, type of rifle (air gun, rimfire. etc.), scope height, magnification, fps/velocity, what you want you're zeroed range to be, and it graphs it out for you. You then can dial in the values to get those two zeros in the line, or not depending on how you shoot.
Quick, easy, and so for has been a solid source for me.


hers a link to the free download on hawkes site: https://us.hawkeoptics.com/x-act.html

"Mrod.25"@18.13 I have it as well but without physically testing the data there is no way to be sure its true. Now some people do that, I just prefer to confirm everything, I have learned it makes taking tricky shots that much easier! Thanks for the input though.

Click to expand...

I have learned if Chairgun is not spot on the data I put in was off, scope height, fps, bc,

Ring height matters too. Tall rings tend to give a longer "sweet spot" where your vertical strike is within one inch, than low mounts. The problem with tall mounts with some guns is getting a good cheek weld.

I've found scope height really comes into play when you are shooting inside/closer than where your first zero lies i.e. if you are sighted in at 25 yards and you are shooting at 10/15 yards, the higher your scope is mounted, the higher you have to hold Over your target. Or shooting at more extreme angles up and down you have to hold Under. The higher up your scope is mounted the more drastic you are effected in these situations.

Didn't realize that having higher mounts could be beneficial, might need that one explained a bit more to me.

As far as how I sight my optics in, I try to find the range where both zeros land on the line together, effectively making one zero. That way I know if I am beyond my zeroed point I will always hold over (in normal flat shooting), and when I am inside my zero I will also hold over. (I think I just said what bob_o said)
Even if I am regularly shooting closer distances, just my way, find it simpler to always know if I need to adjust my aim anytime due to range it's always a hold over.


this video by Ted, may he be blessed forever, is a good one that I learned a lot from https://www.youtube.com/watch?v=zWYcsRr7T6E 

I did a really long and detailed post on scope ring height effect, but the system logged me out just as I hit submit. This is a shorter and kinder version.
Two pictures are below, the first is with high rings (2.75 inches), and the second is with low rings (1.5 inches). Both pictures are with the same round with the same ballistic coefficient and same velocity. The zero point set was 50 yards (in my case, for deer hunting with the Benjamin Bulldog). The only changed factor is the height of the rings. Hawke Sport Optics Chairgun Pro was used for the images.

High rings give a long and continuous range where all shots are within 1 inch of the aim point.



Low rings give a discontinuous set of two ranges where the strike is within 1 inch of the aim point, and are less usable in the field.

Mrod if you put the data into Chairgun and hit optimum zero it will show you where to sight your gun to get that curve that stays in the kill zone the longest. Lower mounts the closer in your curve will be, higher mounts will make the curve farther out.

What 18.13 said. 
Addertooth, you can get a similar, if not identical, result by adjusting your zero distance (closer) with the shorter rings. The advantage to this is it lessens the amount of hold over when you are inside that zero, leaving less room for error when your target is in closer. Which is a good thing in hunting, your targets are rarely right at your optimum zero. According to what i'm getting, with shorter rings 1", the optimum zero lands around 30 yards, placing every shot from 5 yards to 30 yards in that 1" range.

In favor of taller mounts: it would appear, according to the data that i'm getting from X-Act, if you know you are going to be shooting longer distance consistently, the taller rings would be a good way to go, because they do allow you to get that optimum zero at the further range, but you will have to be more mindful of more hold over when inside that zero. This is why Ted was so excited about the FX limitless adjustable mounts. Before Addertooth explained it, I thought Ted was just digging the fact they were adjustable, and I felt that them being so tall was a by product of that function and a person just had to deal with that, but now I see that for those who are regularly/exclusively shooting long distance, the taller mount is probably the better choice.

Comes down to personal preference. When I shoot, I prefer to to be as flat from the barrel to optimum zero, even if that brings that zero in closer than I will be regularly shooting, and know that once I am beyond that zero I hold over according to the distance. Especially if you have a mildot or moa reticle.

i beleive the thinking where lower rings are always best comes from shooting center fire, like .243 and the like, that bullet flies so flat, if you zero in at 50 yards with 1" rings, that optimum zero is good from 5 yards to 200 yards (for 1- 1.5inch groups...ish) before you begin needing to do hold overs of serious consequence (according to the graphs). I've only ever had my .243 zeroed at 75 and shot in the 50-100 yard range, not much of a distance shooter.

Harmless, 
Yes, if the second picture had been zeroed at a short distance, like 25 to 30 yards (note: I went back and played with ideal zero range for short mounts, it was 42 yards), then the two groups would have likely met. I tend to shoot longer distances than some, once again, what people would call hunting distances. I have heard of people hunting at 5 yards, but that close, a rock would serve just as well. Where I live the critters are a bit more shy, and there isn't much in the way of deep forest to obscure your approach. This makes shot distances longer here. Keep in mind the "total number of yards" which you are in the sweet spot (the sum of the two groups on the lower picture, versus the total number of yards in the single top group) still favors the top picture which depicts the tall mount. This is because a high mounted scope must be "pointed down" more, which puts it in better alignment with the downward trajectory of the pellet/round (a better least squares fit to the ballistic path of the round). This is why there is a greater distance of Near Match (within one inch), with the tall mounts.


If all I shot was ten meter match, there would be no benefit to any given mount height; but then, that is not my type of use. If you shoot at shorter distances, then a high mount has no value for you (once again unless it gives you a better cheek weld to the stock). If I shot a high velocity round, like a gunpowder 243, then the flat curve would not get the same benefit from a high mount, velocity matters; but then, we are talking about air rifles in this forum. But your point is still valid, we may some day see airguns achieve velocities which will make any argument for high mounts moot.

Just a added note< For the kill zone in Chairgun I use .38 for .25 cal. and .33 for .22 cal. that way part of your bullet will be touching where you have your crosshair at any distance within your sweet spot.