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Selecting a distance for zeroing my sight

5K views 10 replies 7 participants last post by  Kilerham 
#1 ·
This isn't a question, although I appreciate feedback. I recently bought my first rifle. I'm currently shooting paper, exclusively. I was struggling with zeroing the red dot at an indoor range. I knew the bullet would follow a parabolic trajectory, but I wasn't aware how pronounced it would be in the first 50 yards.

After Googling people's opinions on the distance they zero their red dot sight on a 10/22, it seemed like everyone had a different opinion. And, no one was backing them up with data. Then I found this ballistic trajectory calculator. These graphs are just what I needed to understand where to zero and roughly where to aim.

Before I ran all the calculations for various zero's, I wanted to check the calculator's work. I googled the ballistic coefficient for my favorite ammo and filled in the rest of the values.

CCI:


Shooterscalculator.com:


The results checked out with CCI's provided values. Good. I knew I wanted to zero my red dot at 25 yards or less. When shooting >50 yards, I'll likely swap out my red dot for my scope. I created four zeroing distances on the multiple trajectory graph:


Evaluation:
  • 25 yards offers the flatest trajectory to ~50 yards with 3/4", 1/2", and 1/4" at 10, 15 and 20 yards, respectively.
  • 20 yards doesn't offer anything I'm not getting from 25 yard zero.
  • 15 yards seems reasonable for close range plinking. -1/2" at 10 yards, +1/2" at ~22 yards. This zero would probably be best for my father's eyes, if he were shooting this rifle.
  • 10 yards would leave a lot of correction for close ranges. But it's very flat from 40 to 80 yards. I might choose a trajectory like this for my scope.

I'm going to zero my red dot sight at 25 yards. The flat trajectory requires the least amount of correction for the distances I'll be shooting. There's only a little more than 1" of correction between 5 and 65 yards with this adjustment.

Looking forward to taking this to the range tomorrow. I hope my rifle's muzzle velocity isn't far off from the manufacturer's spec.
 
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#2 ·
Your approach is giving you a zero that gives you "max point blank range" (MPBR) for a target that is 2" in diameter. That's the approach used by many hunters and plinkers. You may enjoy googling on the term to read more about it.

Most matches involving 22lr rifles are shot at 50 yards hence it being a common range for getting sighted in.
 
#3 ·
As your charts clearly show, in most cases there is a "near zero" and a "far zero". A lot of people don't get that and, especially with rifles, there's usually no reason to be aware of the near zero. The reference point is the far zero, not the other one. if you talk about a 20-yard zero you'll just confuse people and the advice you'll get will confuse you.

As long as you know which one you are dealing with at any time, it doesn't really matter but the far zero is the one to concentrate on. It's also better if you're going to shoot at say 50 yards to zero at that distance than at the near zero. Of course if you're dealing with a short indoor range or other limitations, you do what you can. Just don't lose track.

If you're swapping the scope & dot, you should check the zero each time. Don't count on it not changing unless you've confirmed it. Also confirm the ballistics calculations at the range. The math might be perfect but your gun, ammo and conditions are not.

With the homework you've already done, you're already ahead of a lot of people. I expect you to work out a satisfactory answer that's your own. What you need to do now is go shooting.

BTW, my favorite balistics calculator is http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi. No graphs but good detail.
 
#6 · (Edited)
To go with Sophie and CardPuncher, here is a chart I made up for using MPBR zero sighting. It may not be 100% accurate do to all the variables, but it seems to work for me. It is for ammo I was able to get and get the B.C. and velocity for. I haven't ran into any 36gr mini-mag around here.
Good job! "it seems to work for me" is important. There's so much information around here but you have to make it your own.

But you meant grains, not grams, and I hope that's what the calculations were based on. 40 grams is about 617 grains.

...
BC ? I think .1 is about as good as it gets for 22lr. You don't see BC info listed often for 22lr....As for BC I use JBM http://www.jbmballistics.com/cgi-bin/jbmbcv-5.1.cgi With your CCI data it spit out .129 BC ...
Are you contradicting yourself there?

This link is to some posts with a large number of BC's as provided by the manufacturers. The range is from less than .1 to about .15. I usually use .12-.13 unless I'm going to look it up. BC is said to change when going from supersonic to subsonic and in the transonic range. Another reason for reality-checking your results.
 
#5 · (Edited)
I was down this road not long ago and it's one of those things once you get it , well you get it.
The ballistic calculators are ok and will help get you close.

The key to your zero is you expectations and your actual use. If you don't have a tiny little 1/2 moa dot or less that red dot will have an effect on your results as the dot will cover more of your target as you shoot at greater distance.
It gets interesting once you get MOA and how it plays with everything.

As far as velocity goes. CCI responded to a email that I posted in the ammo section that all thier testing is done on 24" test barrels for velocity , pressure and accuracy.

don't forget sight height also . It's not a huge factor but will change your data some.

BC ? I think .1 is about as good as it gets for 22lr. You don't see BC info listed often for 22lr.

As for ballistic calculators there are many and I use several
For quick down and dirty zero info I use the Nikon spot on.
It has one of the largest selections of 22lr ammo pre set into it. It's great for finding out that POI vs POA at close targets to be zeroed at a greater distance.

Hornady calculator works well for me on the desk top.
I have Hawke X-act and chair gun pro on my phone as it just seems to work well with 22lr along with air rifle.

It would be nice if there was a dedicated rimfire app

As for BC I use JBM
http://www.jbmballistics.com/cgi-bin/jbmbcv-5.1.cgi
With your CCI data it spit out .129 BC
Have fun
Oh for my fun plinker I generally shoot 4" plates from 25 to 100 yards. Sounds funny but I can zero around 10-12 yards poa/poi and if I can hold the shot hit 4" plates out to about 90 yards ...I will hold a tad high over 75 yards just to give me some wiggle room. At 100 yards I need to hold the very top edge to just catch the bottom 1/2" or so
 
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