Sight in distance and managing my expectations

[Willydog]

My new Avenger arrived late Sunday afternoon and I quickly slapped on ATN 4K Pro scope on it and sighted it in for 50 yards. At 50 yards on bags, you can’t miss. 18.13 JSB’s at 862-870fps should run right at 30 fpe. 



I got some time today and decided to stretch it out to the max distance of my range, 90 yards. I found my holdover for the ATN, it’s about 10 inches. Once I got it dialed in, I can put round after round into a coke can, no issues except the pellets have so little energy left, they can’t poke a hole in the can. 



I decided to move closer in to ratting distances, 5 - 25 yards. 25 yards was fine. 5 yards required a 3 to 4 inch holdover. Way too much. My trajectory must look like a rainbow.



I know I could just turn up the power and flatten it out,but then I’d be way over for closer stuff. I’m thinking I need to lower my expectations to about 75 yards, but what’s a good sight in distance? 35 yards? Or closer? Most of my shots will be in the 5 to 40 yard range, but 75 - 80 yard shots do come up on occasion.

 

[biohazardman]

Your trajectory at five to 25 yards is likely not a rainbow trajectory but very flat. The problem you are having is the distance between the barrel and the scope height that you have to allow for. Many will sight in somewhere in the 15 to 25 yard range and try not to have to much in the way of hold under from 25 to 40 or 50 yards. But hold over at the closer ranges of 5 and 10 yards is a given and depends on your scope height.

Edit;

Lots of trajectory charts and graphs around.

https://duckduckgo.com/?q=pellet+gun+trajectory&t=ffab&atb=v180-1&iax=images&ia=images

 

[JimNM]

I would suggest you use an apex zero. Find out where in the trajectory the pellet is the highest and make that year zero point. After that all you have to do is have your holdover. You hold over for the clothes shots and you hold over for the long shots. You also have a point blank zero range, which is where the pellet is within an acceptable amount of variance from the zero line.



Also be aware that your scope in the barrel are not parallel. The barrel has to launch the pellet at an upward angle for it to ever meet the line of sight.

 

[dizzums]

typical 900fps ideal sightin is 20y deoending on scope height .. get it in the wrong place and youll never have a long point blank range, just spots that its dead on ... airguns do have a very pronouned arc trajectory and your scope line of sight intersects it depending on zero .. the idea is get it in the ideal spot to more or less 'skim' the top section of the arc to maximize your zero range .. outside of it you will holdover .. and its a matter of getting to know it .. keep all your guns in the same general fps range and theyll all have the same basic holdover characteristics ...you want to get pests every time at all different distances you got to get the concept .. doesnt apply to turret twisting paper pounders as much ..

 

[esingle]

Hello at close range your height of optic above bore line always comes into play, especially the higher you go. If you do not want hold over another option is mounting a small red dot on an offset mount with a 10 or 15 yds zero. Just another option happy shooting Eric

 

[OldSpook]

My new Avenger arrived late Sunday afternoon and I quickly slapped on ATN 4K Pro scope on it and sighted it in for 50 yards. At 50 yards on bags, you can’t miss. 18.13 JSB’s at 862-870fps should run right at 30 fpe. 



I got some time today and decided to stretch it out to the max distance of my range, 90 yards. I found my holdover for the ATN, it’s about 10 inches. Once I got it dialed in, I can put round after round into a coke can, no issues except the pellets have so little energy left, they can’t poke a hole in the can. 



I decided to move closer in to ratting distances, 5 - 25 yards. 25 yards was fine. 5 yards required a 3 to 4 inch holdover. Way too much. My trajectory must look like a rainbow.



I know I could just turn up the power and flatten it out,but then I’d be way over for closer stuff. I’m thinking I need to lower my expectations to about 75 yards, but what’s a good sight in distance? 35 yards? Or closer? Most of my shots will be in the 5 to 40 yard range, but 75 - 80 yard shots do come up on occasion.

Here you go. This presumes a sight height of about 3.5" which will likely be "close" to what you are using. The intercepts in the drop graph on the lower left will only agree with your sight when you are set to your second zero (47.3 yds) and using a reticle graduated in mils or half mils.

 

[elh0102]

I would suggest you use an apex zero. Find out where in the trajectory the pellet is the highest and make that year zero point. After that all you have to do is have your holdover. You hold over for the clothes shots and you hold over for the long shots. You also have a point blank zero range, which is where the pellet is within an acceptable amount of variance from the zero line.



Also be aware that your scope in the barrel are not parallel. The barrel has to launch the pellet at an upward angle for it to ever meet the line of sight.

I also like this technique. Holding under is, for me, counter intuitive, so having all holdover seems easier for me.

 

[OldSpook]

Different strokes for different folks.

The idea of an optimal zero is simple enough for anyone to understand. This is also sometimes called a point blank or a point on zero. The rifle is zero such that the pellet rises until it rises one half of the width of the killzone above line of sight. And then drops until it falls below 1/2 of the width of the killzone. In this manner zero is set up so that the maximum distance which the shooter can simply aim at the center of the kill zone is established.

In the example above the point on distance runs from about 20 yards to about 50 yards. Between 20 and 50 yards the shooter can simply aim at the center of the killzone and expect to strike within the killzone.

In this particular instance most of your targets will probably appear in that 20 to 50 yard range. Inside 20 yards you need to aim a little bit high because the pellet is going to strike low. Outside 50 yards you need to aim high because the pellet is going to strike low. The majority of the time neither hold over nor hold under is necessary.

It ain't rocket science.

 

[BackStop]

The easiest way I know is to get Chairgun Pro and choose Toolbox - Zero Range Functions - Optimum Zero from the pull down menus.

Make sure you have all the other data set correctly and don't forget to set the Kill Zone size for your intended target(s). This will make your PBR longer or shorter depending on how small you make the kill zone. For chippers, rats and squirrels I set this to .25 (1/4 inch) for my .177 Fortitude shooting 10.5g pellets @ 750fps. This means that within the PBR, the pellet is never higher or lower than 1/8 inch from the center of the Kill Zone.

My PBR is ~15 to ~31 yards and holdover (or clicking the elevation turret) is necessary for anything outside of the PBR.

I use holdover and don't click turrets. It is simpler for me (and I don't trust the scope to be consistent and repeatable) and fairly easy to remember the holdover since most of my shots are between 13 and 40 yards with the large majority of them falling within the PBR range.

I have never used Strelok, but I am pretty sure it can do the same.

P.S.

Both Chairgun and Strelok are capable of creating "Range Cards" for holdover which many people find very useful!

 

[elh0102]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

 

[bandg]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

Agree. Sight height should be related more to a shooters build and comfort. Some will prefer a low scope and some will prefer a higher scope. Personally, I like them higher than most and that aids a bit in the extension of MPBR (the distance range where a shooter can hold on the target and expect a hit). I've always used the two zero method of sighting for any of my hunting/pesting setups. Allowing the shot to rise slightly above LOS (but staying within the hit distance) extends the MPBR somewhat and can be quite useful for many shooters. If I were shooting at paper at a set known distance then probably the single zero method would be more useful. Different strokes.

 

[OldSpook]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

So you have never owned one of the ATM X-Sights.

I have to admit the one I have is not the same model as his and the 4k might mount lower.

@Willydog if you will measure the distance between the center of your bore and your X-Sight I'll make up one of those specifically for your setup and post it here.

You will find the resultant table to be approximate.. It will inform your shooting. I often use such tables and take particular pleasure out of "tweaking" the model so that it agrees with the actual shooting.

There are other "low tech" methods of achieving the same thing and they are every bit as accurate.

 

[OldSpook]

Here is an "old school" method of calculating your "point blanch range" zero. You don't need a chronograph, or a computer to use this target system. I drew up these targets few years ago and just noticed the links to them (here on AGN) are broken because I moved the targets on my server. I will go fix those links by recreating the path they call out here at AGN. Anyway here is the PDF

View attachment drop-chart.1635464057.pdf

 

[elh0102]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

So you have never owned one of the ATM X-Sights.

Correct, have not. But, in over 50 years of playing with this stuff, I've yet to find a substitute for a day at the range. 

 

[Willydog]

I’m just now getting back to this. Centerline of the scope is about 2 3/8” over the centerline of the bore.

OldCrow: your chart is pretty close to what I’m seeing, not exactly, but pretty close. My curve has a bit more arc to it, but that chart is going to help me a lot. Thanks.

I’ve had this ATN since Christmas but I haven’t played with it much, I was waiting for the gun. The first reticle I used was the mil reticle and it was way off, so I switched to one of the more standard reticles. Then going through the menu, I realize the hash marks were set to 4 moa. I changed it back to 1 moa and it makes more sense now.

Reading through the manual, I can save different scope profiles. So I guess realistically I can set one profile for a short range zero and a second profile with a longer range zero. Say set one for 20-25 yards to get a more level trajectory from 5 - 40 and a second one at 60 to cover 40 to 75. 

 

[OldSpook]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

So you have never owned one of the ATM X-Sights.

Correct, have not. But, in over 50 years of playing with this stuff, I've yet to find a substitute for a day at the range.

You know if you actually go ahead and read what I wrote you'll figure out we agree.

By the way between the two of us we have about a hundred and 15 years of shooting experience your 50 and my 65, but who is counting?

 

[OldSpook]

I’m just now getting back to this. Centerline of the scope is about 2 3/8” over the centerline of the bore.

OldCrow: your chart is pretty close to what I’m seeing, not exactly, but pretty close. My curve has a bit more arc to it, but that chart is going to help me a lot. Thanks.

I've got a doctor's appointment tomorrow but when I get back I will use the new numbers to make you a better chart.

 

[elh0102]

The assumption above of a 3.5" sight height might be right for certain applications, but it's way higher than any of my rifles, which are closer to 1.5" above bore. But, this is one of many variables that contribute to error in any artificially generated data. IMO, there is no substitute for shooting, for both its practical value and fun.

So you have never owned one of the ATM X-Sights.

Correct, have not. But, in over 50 years of playing with this stuff, I've yet to find a substitute for a day at the range.

You know if you actually go ahead and read what I wrote you'll figure out we agree.

By the way between the two of us we have about a hundred and 15 years of shooting experience your 50 and my 65, but who is counting?

I've read all your comments and I agree, the use of technology can assist in getting a rifle zeroed in whatever manner you choose. Your points are well taken and I didn't mean to overlook or disrespect your position. I prefer to just go out and shoot, but I realize I may be doing it the hard way. Maybe I need another 15 years of experience to see the light! Great comments, thanks. 

 

[OldSpook]

I’m just now getting back to this. Centerline of the scope is about 2 3/8” over the centerline of the bore.

OldCrow: your chart is pretty close to what I’m seeing, not exactly, but pretty close. My curve has a bit more arc to it, but that chart is going to help me a lot. Thanks.

...

Reading through the manual, I can save different scope profiles. So I guess realistically I can set one profile for a short range zero and a second profile with a longer range zero. Say set one for 20-25 yards to get a more level trajectory from 5 - 40 and a second one at 60 to cover 40 to 75.

Well then you will want two drop charts with different sized "kill zones". KZ is 3/4 inch for squirrels.

Here is one for rabbits and ground hogs out to 80 yards. KZ is 1.5 inches.

Wind drift is calculated for a 1mph wind from 270 degrees ( a full value one MPH drift). Drift and drop are also shown in mil dots. Intercepts (far right of the trajectory graph) are in mil dots and yards (near:far).

Set up with either of those zeros and on a CALM day shoot a five shot group at the farthest range you can get, preferably around 60 yards. Send me an image of the group with the aim point clearly marked. Put a coin or ruler on the picture so I can compute measurements from it. I will remake the charts so that it reflects YOUR BC for that pellet from your rifle. Mind you BC changes with velocity but not really all that drastically so it will be closer than you can shoot when it is done.

Just PM me when you want me to do that.