2 zero's or zero at apex

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josh3rd

josh3rd

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Apr 2, 2015
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Newark, Delaware, United States
I have a AA Prosport shooting at AA Diabolo 8.4gr @ 765fps. I usually have it sighted in at 25yds which is at it's apex so all my aim points from 10 to 55yds are below the crosshairs or I should say all my aim points, aside from my zero, are holdovers. Anyway on Chairgun I use a .5" KZ and with it sighted in at 25yds CG says that i'll be within a 1/4" below my zero from about 17yds-32yds. Now if I use the optimum zero range with a .5" KZ my near zero is 18yds (which is -.01") and my far zero is 33yds (which is 0.0"). 

So with that information, which one is "better" so to speak. It seems like both options are equal. Thank you
 
I don't think either one is "better", they are just different. It probably depends on the size of the "kill zone" as you say, as well as ballistic arc and scope mounting height. I always try to use a two zero setup but it's just how I learned to do it years ago.

Consider trying to break an aspirin tablet. With single zero, how wide would the MPBR be? Then consider two zero with the pellet never rising high enough to miss high. You would have a wider MPBR. How much wider? That would depend on the factors mentioned above. Different approaches each probably having certain advantages.

Could well be wrong but it seems if you know the exact distance to the target then possibly single zero might do better but if the range isn't known exactly then maybe two zero would help.
 
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I think it depends if you routinely shoot at longer yardages. Using the apex of your trajectory as the single zero will only allow you to zero the gun at a fairly close range. You may not be able to zero at say 50 or more yards, because to hit at 50+ yards it's likely your trajectory will rise above the POI, therefore giving you 2 zeros. 

If you only use one zero, and if it is fairly close (25 yards) you will need to use a lot of holdover at longer ranges because the pellet is rapidly falling and the arc is on a steep downward trend. That means that with that situation for every yard of added distance the amount of holder needs to be greater. With 2 zeros the trajectory arc will be flatter and your ability to judge holdover easier. In the end it comes down to what works best for you.
 
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. . . the use of light pellet, zero'ing @25 yards and the use of "KZ" smacks of field target. ;-) I've seen several references and have (more or less) adapted the same for myself ( for 20 ft/lb FT ) where zero'ing between 25-30 yards will typically result in most targets on a FT range being hold overs. ( just to keep it simple - hold over only - no hold over for X distance, hold under for Y distance ) With my M-Rod (.177) 28 yards zero seems to be pretty close to this "sweet spot". 10-19'ish yards are hold over - especially 15 & under. 20-33'ish or so are actually pretty flat - basically put the cross hairs on the target and wack it. 34 out to 55 need to start holding over again - more so as you get further out.
 
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Interesting question. For actual hunting, I always zero at 35 yards, which on my gun will have me within 1/4" from around 15 to 40 yards. So I don't have to worry about holdover/under until distances go beyond 40 yards.

But for field target, the concern is going to be errors in range estimation, and it shouldn't matter much which zero method is used. As an example, if you zero at 25 yards with a 12 ft-lb rifle and use holdover for 50 yards when the target is really at 55 yards, you will hit 1.4" low. Evaluating the same scenario for a 35 yard zero you will hit 1.3" low, almost the same. You might want to check this yourself using the inputs for your setup. But in any case, the difference will be small and you might as well use whichever zero method you feel comfortable with. I can see some definite advantages to the apex zero method as it would eliminate any confusion between holdover and holdunder.
 
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Interesting question. For actual hunting, I always zero at 35 yards, which on my gun will have me within 1/4" from around 15 to 40 yards. So I don't have to worry about holdover/under until distances go beyond 40 yards.

But for field target, the concern is going to be errors in range estimation, and it shouldn't matter much which zero method is used. As an example, if you zero at 25 yards with a 12 ft-lb rifle and use holdover for 50 yards when the target is really at 55 yards, you will hit 1.4" low. Evaluating the same scenario for a 35 yard zero you will hit 1.3" low, almost the same. You might want to check this yourself using the inputs for your setup. But in any case, the difference will be small and you might as well use whichever zero method you feel comfortable with. I can see some definite advantages to the apex zero method as it would eliminate any confusion between holdover and holdunder.
Click to expand...

Your numbers don't seem quite right. Zero at 25 yards hits lower at 50 than zero at 35 yards does? Seems it should be the other way around.

And note, if you keep your rise within the kill zone radius then you don't really have any holdunder. And you will always deal with holdover at some distance (near or far), just maybe not for FT only shooting distances if they are known relatively exactly.
 
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The two zero approach works well for me in HFT. Yes I have to hold under a little (1/2 - 1 dot max) sometimes but my driver is that I want the second zero as close as possible to the point at which the scope begins range finding less well. Lets says that's 35yds. At 55y I'm still only holding over by 2 dots max as the hit zones get bigger. Works for me. 

Your numbers will differ. I'm shooting an 18fpe PCP and I thing your shooting the 12fpe prosport. But... my numbers are not all that much different with my 12fpe FWB800...
 
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Bandg, sorry if my explanation wasn't clear. For hunter FT I assume most people will estimate distance as best they can, then consult a range card to find the necessary holdover. The effect of being off on the range estimate for the two zeroing approaches was what I was trying to illustrate. The scenario was estimating the range as 50 yards, when it was actually 55 yards. With either zeroing method, if you use the calculated 50 yard holdover hits will be low.

With the 25 yard zero, your 50 yard entry on the range card will tell you to hold over 3.4", but since the target is actually at 55 yards, drop is actually 4.8" so you hit 1.4" low.

With the 35 yard zero, the 50 yard card entry says to hold over 2.4", but at 55 yards the drop is 3.7" so you hit 1.3" low, about the same.

Thus for either zeroing method the effect of range estimation error is the same, and you might as well use the method you prefer. Personally I like the idea of being always able to use holdover, which is what you get with the apex zeroing method.
 
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