Methods: How do YOU make sure your "Optimum" zero is correct for 2 PBR zeros?

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BackStop

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Wow, that IS a mouthfull... (chuckle)

OK, by using a ballistics program like Chargun Pro or Strelok you can plug in your data and the program will tell you what your optimum zero range is. Right?

OK, if you sight-in your scope at that "optimum" distance, how do you KNOW that you are truly sighted in at the optimum range?

There is VERY little difference in the POI within a specific range near the optimum zero distance, so it is hard to actually KNOW you are sighted in "optimally".

I mean, in my case, I set my kill zone at .25 or one quarter of an inch which is less than 2 widths of the .177 ammo I shoot.

Anyway, the only way I have come up with, and this is not always possible for many people, is to sight in the airgun at the "optimum range" and then set the target to the minimum and maximum PBR ranges and see if they are still within the kill zone and with the appropriate drops within the KZ.

THEN, I test closer and farther than the PBR (at measured distances) to see if the holdover/holdunder matches what I expect and/or what the ballistics program says it should be.

I guess my question is... is there an easier/faster way that is more precise or at least AS precise? I haven't even been able to find an article that refers to this, although I may have not used the correct/right search terms. (smile)
 
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Yes in Chairgun:
Toolbox -> Zero Range Functions -> Optimum Zero Range

Verifying a scant 1/4" change in elevation at both ends of the PBR range is not a trivial thing because the basic accuracy of most guns + shooter + environmental conditions will not clearly reveal that degree of resolution. The answer would then seemingly be to shoot enough to ferret out the average elevation. But I would suggest that's a bad way to do it. We concern ourselves with making ethical kills so I think a better way to look at it is over what range will the worst of my shots reliably hit the kill zone of my quarry. That is, with the full myriad of factors taken into account...not just the textbook calculation for elevation change.
 
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nervoustrig said:
Yes in Chairgun:
Toolbox -> Zero Range Functions -> Optimum Zero Range

Verifying a scant 1/4" change in elevation at both ends of the PBR range is not a trivial thing because the basic accuracy of most guns + shooter + environmental conditions will not clearly reveal that degree of resolution. The answer would then seemingly be to shoot enough to ferret out the average elevation. But I would suggest that's a bad way to do it. We concern ourselves with making ethical kills so I think a better way to look at it is over what range will the worst of my shots reliably hit the kill zone of my quarry. That is, with the full myriad of factors taken into account...not just the textbook calculation for elevation change.
Click to expand...

In my case, I am using an extremely small "kill zone" because I want to be as precise as I can be, given that my targets are small, for a clean kill. Chipmunks and tree rats.

From experience, I know that making a clean kill on either, especially on the chipmunks, requires .25 inch precision for consistent clean kills. I like heart shots as they produce the fastest, cleanest kills when done well. Stop the heart and they drop, and they don't bleed out. I stopped going for head shots because .25 inch off and you don't have a clean kill. Yes, I also read about "heart shot" animals running away for a distance. When done well on chipper and tree rats, they don't run far, if at all. Even with .177 domes. Some people will go to a higher caliber and higher FPE, but I don't have that option in this residential area and I truly believe those folks are fudging because of lack of accuracy/precision.

The quarter inch kill zone is what I zero for and (until recently) have attained with consistency in the Fortitude. Especially on shots less than 25 yards and often on shots out to 50 or more yards (1 MOA at worst) and as I posted recently, I took 3 tree rats at ~75-80 yards... (all DRT heart shots) although I know there was some luck there.

Regardless of the size of the kill zone, do you have a better way to verify the PBR than what I described? All I am really asking is even if you set the kill zone larger, how do you really know that you are zeroed at that precise point, unless you shoot at the extreme ends of the PBR and then outside of it to make sure of holdover outside of the PBR. I think this is more important for my situation than it would be for more powerful, higher caliber airguns or PB rifles where the kill zone is usually MUCH larger.

Yes, my .25 inch kill zone is small. But for the sake of argument, make it larger and then answer the question? (smile)

p.s.

Thanks for the reply!
 
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I think you're on the right track regarding shooting at greater distances where the drop becomes more pronounced. As early as 50-55 yards, the POI of a typical pellet will be down by 2" or more. So although accuracy is simultaneously degrading as the distance increases, the drop will generally be growing at a greater rate. If it matches up neatly with the software's prediction (assuming all the proper inputs like BC, velocity, scope height, etc.), you can reasonably conclude it's zeroed at the optimum distance suggested by the software.

Though I'm still of the mind that the overall accuracy is a better metric. And the smaller the kill zone I'm trying to hit, the less willing I am to use a PBR window because at the ends I'm conceding a shot placement that will land low, and in the middle I'm conceding a shot placement that will land high. I'd rather consult my range card and center my point of aim to give myself more margin for error. Granted I do realize there are circumstances where the PBR window represents a necessary compromise such as when shooting pests that don't sit still for long like mice.
 
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nervoustrig said:
I think you're on the right track regarding shooting at greater distances where the drop becomes more pronounced. As early as 50-55 yards, the POI of a typical pellet will be down by 2" or more. So although accuracy is simultaneously degrading as the distance increases, the drop will generally be growing at a greater rate. If it matches up neatly with the software's prediction (assuming all the proper inputs like BC, velocity, scope height, etc.), you can reasonably conclude it's zeroed at the optimum distance suggested by the software.

Though I'm still of the mind that the overall accuracy is a better metric. And the smaller the kill zone I'm trying to hit, the less willing I am to use a PBR window because at the ends I'm conceding a shot placement that will land low, and in the middle I'm conceding a shot placement that will land high. I'd rather consult my range card and center my point of aim to give myself more margin for error. Granted I do realize there are circumstances where the PBR window represents a necessary compromise such as when shooting pests that don't sit still for long like mice.
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Hahaha! You forget that most of my shooting has been with the Fortitude at ~750fps/10.5 CPUM... so that drop comes into play sooner than the average airgun shooter.

The DAR seems to be shooting fairly consistently at ~850fps, but is still not grouping well or consistently. Maybe it just needs to be shot more, but I was spoiled by the Nova Vista Freedoms that shot sub MOA almost right out of the box! (grin) If it ever starts grouping well, it will be my goto for anything farther than the PBR of the Fortitude. Not to mention that the Athlon on the DAR will NOT focus down to 15 yards at its highest power and is still fuzzy at 15 yards, even though Athlon claims it will focus to 15 yards. Not a bad scope, just not good for close range unless you like to shoot at fuzzy targets.

As I think I said, my kill zone in Chairgun is .25 inch. That means that my PBR is ONLY 1/8 inch high or low. You may be using a much larger kill zone. This also helps me to REALLY know what my hold over/under should be. Yes, I am all about accuracy/precision. When my tools can do it, I can do it... most of the time. (chuckle)

So, I KNOW that within my kill zone/PBR I am only going to be off by 1/8 inch, if the gun is consistent and I can do my part.

I think most people use a much larger kill zone, higher velocity and larger caliber. I can't do that in my situation. But I believe that has made me a much better shooter.
No, it has REQUIRED me to be a better shooter! (smile)
 
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At some point ALL OF US will require some amount of "Hold Over" .... with such reality if using calculated D.O.P.E. it likely will prove best to use ONE PBR and just hold over when under or over that single PBR distance.

As in the game of Field Target where we too are limited on power, an absolute SINGLE PBR is key where we NEVER hold under at any time. Your either dead on being generally @ 26-32 yards or holding over some prescribed amount via a D.O.P.E. chart.
 
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Not counting field target (where you are limited by rules) you should just initially check that your Strelok inputs are correct and then use a laser rangefinder and aim exactly where Strelok tells you to. Don't use a pbr setting if you are worried about being off a little bit. If you don't have the time to range and use Strelok, don't take the shot. Trying to set up your zero within a size constraint and then saying that you want as much accuracy as possible is counterproductive. JMHO
 
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theres always factors outside what the program tells you ... i dont bother trying to iron it out, and really ive found between .75 and 1" kill zone yields acceptable results ... i have a range set up with a small aluminum target every 10 yds out to 50 .. if it bangs every one of them in succession its 'on' .. then i go for targets beyond 50 and see what the holdover is, and most guns are needing holdover by 55 depending on velocity, pellet etc will determine its drop characteristics .. if it dont feel right with the scope and setup im using i might adjust it a click or two, then re-smack my 10-50 targets to see if thatl work ...
...also, for 'tighter' sightins on say tiny targets, its best to reduce range .. hunting chipmunks at 75yds isnt really feasible with any degree of reliabilty if you want to keep a 1/4" killzone .. but limiting it to 30 40 yeah, that works.. i like keeping velicity high .. velocity is your friend when hunting and dealing with banana shaped trajectories ..
 
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DonaAna1 said:
I can't see a chipper at 75 yards. I too set up targets at every 10 yards. And pbr is only out to 54 yards or so. And to tell the truth, there are very few days where the weather cooperates enough to check PBR.

But OP is correct, the only way to check is to set out targets and shoot and shoot and shoot.
Click to expand...
I have never shot or even shot at a chipper at 75 yards, but both scopes in my signature are capable seeing a chipper at that range. Especially the Athlon.

My extreme pbr on the DAR is only about 37 yards if I use MPBR (optimum zero in Chairgun), but I have dialed it up so my zero is ~40 yards because the Fortitude takes care of pretty much everything less than that.

When I have more time with the DAR, I am going to test the Athlon to see if it is click worthy for range. So far, I have not had a scope I trusted enough to try clicking for range, but the Athlon just might be good enough to do it. I have had the Athlon for quite a while, but did not have a gun to put it on...

If it works, I will be doing some longer range shooting for sure! (smile)
 
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