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More about sighting-in: How to determine the two intersection points

By B.B. Pelletier

The following question was a comment to the June 1 post, At what range should you zero your scope?

Question:
How do you figure out what the two intersections are? Is there a formula?

Just shoot & see
No doubt, a formula could be constructed, but I do it the easy way. Simply aim at a specific point at a known distance, shoot and see where the pellet impacts relative to the aim point. That’s where I came up with the distances I gave in my June 1 post.

Each pellet has a different trajectory
My distance figures in that posting were not exact. They change slightly because each type of pellet has a unique ballistic flight. If it has higher drag, it slows down faster and the trajectory is more pronounced. The figures I gave were for a domed pellet, like the Crosman Premier, which is pretty standard for field use.

If you shoot wadcutters or hollowpoints that have a sharp shoulder, such as the RWS Super-H-Point, your trajectory will be more pronounced because the pellet is less aerodynamic. The difference will be small at close range but will increase rapidly as the distance passes 30 yards. That’s why wadcutters and hollowpoints are not as good for long-range shooting (unless you take the time to learn their performance characteristics well).

Twenty yards is a common zero distance
The initial point of intersection I gave in the posting (20 yards) is based on seven years of competitive experience shooting field target. I had to learn the performance of a great many pellets (all .177, but that makes little difference to what we are doing). Although there are a LOT of variables, I soon noticed that nearly every shooter had a first zero point of around 20 yards. When I tried it myself, I discovered why.

What a precision target shooter wants is the most forgiving zero possible. One where, if the yardage is not exactly what the shooter estimated, the difference in pellet impact point is very small. If you zero your gun so the first impact point is 20 yards, you’ll get another 10 to 20 yards of flat trajectory and any apparent rise or fall of the pellet is less than one pellet diameter. The first intersection is at 20 yards and the second is at 30 yards (a 10-yard flat spot) with a gun shooting around 725-750 f.p.s. When you get it up to 950 f.p.s., the second point will be all the way out to 40 yards. If you go even faster, you’ll have a flatter trajectory but also get blown groups and leading. It’s not worth it.

You CAN stretch out the first point of intersection to 30 yards, if you like. All it takes is a scope adjustment. BUT, your flat spot will be MUCH shorter than when you were zeroed at 20 yards. It may only be 5 yards long. Zero at 40 yards for the first point, and the flat spot MAY be yards long. Get it?

What’s really happening is that the pellet is dropping the moment it leaves the muzzle. You have about 30 to 40 yards to play with before the trajectory is a real downward slide. By zeroing at 20 yards, you get a nice long flat spot and can still adjust your scope or hold-over for distances outside that range.

Will zeroing at 5 feet give me a really long flat trajectory?
At this point you may be wondering why I’m saying 20 yards is a good zero point. Why not zero at 5 FEET and enjoy as much of that flat trajectory as possible? If your scope looked straight through the center of your barrel, you could do that. Because you have to mount your scope high above the barrel, you can’t make it work that way. The separation of the scope axis and bore axis introduces parallax that has to be accounted for when you sight-in.

This is already a long post, so I’m going to end it here and continue this discussion on another day. I hope I’ve answered some of your questions. Please feel free to post comments or additional questions!

author avatar
B.B. Pelletier
Tom Gaylord is known as The Godfather of Airguns™ and has been an airgunner for over a half-century, but it was the Beeman company in the 1970s that awoke a serious interest in airguns. Until then, all he knew were the inexpensive American airguns. Through the pages of the Beeman catalog, he learned about adult airguns for the first time. In 1994, Tom started The Airgun Letter with his wife, Edith. This monthly newsletter was designed to bring serious reports about airguns to the American public. The newsletter and Airgun Revue, a sister magazine about collectible airguns, was published from 1994 until 2002, when Tom started Airgun Illustrated -- the first American newsstand magazine about airguns. Tom worked for three years as technical director at AirForce Airguns, the makers of the Talon, Condor, and Escape precharged air rifles. Today, he writes about airguns and firearms for various publications and websites. He also makes videos, and you'll find short clips embedded in some of his artices on Pyramyd AIR's website. Tom is a consultant to Pyramyd AIR and writes under the name of B.B. Pelletier.

59 thoughts on “More about sighting-in: How to determine the two intersection points”

  1. Your information is great.

    What is the practical range for an airgun.

    What is the “effective” range for an airgun used for hunting.

    Is twenty or 30 yards what everyone shoots at?

  2. I’m thinking thats NO problem, I forget all the stats on what he told me. I do know I shot duck decoys @ 200 to 250 yds w/it.(Rangefinder said 250, guy w/scope said parallex was 225)Either way w/the accuracy & what it does to smaller targets…..I say it’ll drop a deer in its tracks.

    I’ll check w/manufacturer on the ft/pounds, but I’ve seen some amazing results w/these things……They are handmade by a very talented machinist friend of a friend.

    The 30 caliber goes through 2 by 4’s sideways. I realize this shot was at an unmeasured distance but, its probably 75 yards.
    When I get the ft/# numbers I’ll get back to you.
    Thanks

  3. I have never tried a scope of any kind, but am interested in trying one on a pistol. What is the difference between a pistol scope and a rifle scope? Can a rifle scope be used on a pistol? I am assuming a scope marketed specifically as a pistol scope is meant to be viewed at arms length, but can’t imagine what that must be like.

  4. The main difference between pistol and rifle scopes is the eye relief. You have about 20 inches with a pistol scope but around three with a rifle scope. That allows you to extend your arms.

    Pistol scopes are lower powered and they tend to cost about twice what comparable rifle scope do.

    B.B.

  5. 35 feet is 12 yards. That’s a poor distance at which to sight in, but I hear this kind of question all the time because that’s all the distance you have where it is convenient to shoot. So this is what you do. Sight in to strike one inch BELOW your aim point at 35 feet. That should put you very close to dead on at 20-30 yards. If you sight in at 35 feet, you will be off at most other distances.

    B.B.

  6. so if i sight at 35 ft and follow your directions i should be pretty close on target at 20 to 30 yards, but if i shoot a target at 35 feet it will mean that i will shoot and hit 1 inch lower right????

  7. gun is crosman quest ammo is crosman pointed the range is 50 feet i get it to sight in small groups and then they just go all over the place i’m getting frustrated and the scope is a powerline 3-9×32 scope…

  8. Hang in there!

    Is the scope adjusted to the limit either to the right or up high?

    Are you holding the rifle on the open flat of your hand – not touching the stock with your fingertips? Are you holding the stock just forward of the triggerguard? Do you allow the rifle to recoil as much as it can?

    Are you breathing and relaxing before you align the crosshairs? By aligning them before you relax you are sertting the rifle up to throw the shots high and to the right, if you are right-handed.

    It is very frustrating to learn to shoot a breakbarrel air rifle. But the technique I just described is the only way. Shooting off cloth or sandbags is a recipe for failure.

    B.B.

  9. i leave the stock on a pillow to stability….i let the gun recoil as if i am shooting it normally. so i should not use a pillow or anything right??????i tend to shoot more to the left..

  10. I AM SHOOTING TO MUCH TO THE LEFT..I AM HOLDING THE STOCK WITH MY HAND AND FINGERS AROUND THE STOCK… I DONT LET THE GUN RECOIL AS MUCH AS IT CAN…. AND I HAVE BEEN RESTING MY HAND ON A LPILLOW FOR STABILITY… I AM SUPPOSED TO USE A PILLOW OR SOMTHING TO HELP WITH SHAKING?????I GET ALOT OF SCATTERD SHOTS AND THEN I GET A CLOSE SHOT AND THEN THEY SCATTER AGAIN I AM ABOUT TO GIVE UP BECAUSE IT MIGHT BE THE GUN OR SCOPE…….

  11. You need to learn the artillery hold for AN Y spring piston air rifle. They all require it. And breakbarrels are the worst.

    The shakinjg is something you need to deal with. It’s one of the things shooters nbeed to overcome.

    Cloth will not help you. You have to rest a recoiling spring rifle on the FLAY of your open palm.

    I can’t find any blogs I have done on this hold, so I will do a new one for you. Tomorrow.

    B.B.

  12. i really think that it is not the way i hold the gun because i can get the gun shooting where i want it and then it shoots all over the place i am probaly gonna stick with my open sights…….or buy a new scope for the third time the gun itself shoots okay bu not the best when shooting with open sights…

  13. Wow..it’s about 1 meter…that is big…more than i expected really lol
    In the rotating elevation adjustment ,it is said : 1 click,1/4” at 100 yards….what does that mean?
    About how many clicks will i have to turn to get my shots higher to zero at 100 yards?…is it about 160 clicks? Lets say for every click,the shot will go up 1/4 inch for 100 yard distance(0.6 centimeters)….I have about 1 meter to catch up(100 centimeters).Then for 100 centimeters,it will be 100/0.6=166 clicks….
    Is that correct? Does the rotating adjustment rotate that many??

    Thanx for clearing things 🙂

  14. Fouad,

    The scope marking mean what you think they mean.

    Most scopes have not enough vertical adjustment to shoot 100 yards. You need an adjustable scope mount for the rest.

    But instead of talking about it, why not test it yourself? Make an aim point about 3 feet above a large piece of cardboard and see where the pellet hits. If you hit the cardboard (it should be a piece at least a meter square) mark your hit and see how far the pellet dropped.

    Guessing, which is what I am doing, only goes so far.

    Count the clicks in your scope. That’s what I do and they vary widely.

    B.B.

  15. B.B,

    Yes i will try it myself of course,but right now the scope i bought was broke(i told you about it).And it is under repair.The guy said he will make it stronger from the inside so that the crosshair wont rotate anymore…and ALSO this time i will buy a scope stop that has a recoil absorber and i will buy a double mount system so that i can fit the scope stop in between those 2 mounts.
    Do you think this will prevent my scope (Gamo sporter 3-9x 40) from breaking again?

    Thanx,and sorry for asking that many questions,but i hope you dont’t mind …

    Fouad

  16. Fouad,

    That’s a question I can’t answer. It depends on what the rebuilder does. But since he says he can do it, it sounds like he knows what he’s doing. Many scope repair places don’t even acknowledge the difference between airgun stresses and those from firearms.

    B.B.

  17. Hi,
    I recently purchased my first air rifle, a Gamo Big Cat 1200. I followed your tips for sighting in at 35 ft, using Gamo PBA Raptor pellets. I then decided to see how other pellets performed and my problems began. I tried RWS Superpoint Field Line 8.2 grains, RWS Superdome 8.3 gr and RWS Wad cutters and all hit from four to six inches lower than the Raptors and I ran out of clicks on my scope before I got close to the center. Is there something wrong with my initial sighting in? What do you recommend?
    Thanks,
    Ed

  18. Ed,

    You have barrel droop. Have you read our discussions abut it? It’s very common on breakbarrels.

    To correct your scope you either need to shim under the rear ring or you need to use an adjustable mount.

    The Raptors hit higher because they are going so much faster. But you will want to use the other pellet because they are more accurate, so you do have to correct the scope.

    B.B.

  19. Thanks for the quick reply. I’ve quickly read a few of your discussions and did add the 35mm piece “shim” in the rear of the scope mount. I was able to bring down the number of clicks on my scope and got the RWS Superdomes on target at 20 yds. That is ½ “ high at 20 yds. However, when shooting at 15 and 10 yds things got very confusing, and really need your help. I don’t wish to clog up this forum with my problems, so if you wish to write me privately my email address is eforteza@prtc.net. So you know, I’m new at air rifles but been shooting all my life from mortars, M-14, M16 to bows, so I know a little about shooting. However, this really has me scratching my head. As I mentioned before, I’m shooting a Gamo Big Cat with two different pellets, Gamo PBS Raptors and RWS Superdomes. Here were the results with the Superdomes and I did it twice just to make sure. The RWS Superdomes; at 20 yds were hitting ½ high at 20 yds from aim point. When I moved to 15 yds. they were hitting down ½ “ and right 1 ½” from center. When I moved in to 10 yds. they were hitting down 2” and to the right ½”. It doesn’t make sense to me how they went to the right and down, and looped around from 3:30 o’clock to 5:30 o’clock as I got closer. Hope all this makes sense to you. I contacted Gamo and they’re willing to check it out under warranty, but I wanted to see if I can figure it out first before spending on shipping charges. Thanks again, Ed from Puerto Rico

  20. Ed,

    There are two possibilities here, a scope that’s grossly out of alignment or a spiraling pellet. I suspect the latter, because as you go farther from the muzzle, the dispersion changes.

    Spiraling pellets are due to gross instability. That pellet, the RWS Superdome, is wrong for your rifle. If you plot all the hits on a single piece of paper you will see the spiral. From that, you can even predict where the pellet will strike at a different range.

    Don’t expect a Raptor to be accurate at any range.

    The Superdome is too narrow for your bore. You need a fatter pellet. Try some Gamo pellets and try some Crosman Premiers.

    Incidentally, centerfire bullets also spiral, though they do it over much longer distances.

    By the way, I was a 4.2″ mortar platoon leader, so we share some common experiences.

    B.B.

  21. B.B.;
    81 MM, PLT-SGT 0369, 3rdMarDiv, Okinawa, 1973.
    Are you suggesting the Crosman Premiers 7.9 gr dome lights? You mentioned as I go farther from the muzzle, the dispersion changes. What do you mean? In my case the groups move as I get closer. Haven’t tried it longer, until I get it correct from 20 on in. I noticed the information did not type correctly in my previous comment, so to confirm, at 20 yds the hits are half inch high, at 15 yds the group moves right two inches and down one inch; and at 10 yds the group is half inch right and two inches low. At 15 way right and at 10 way low.
    I will contact Pyramyd about ordering the pellets and hopefully get on target.
    Thanks for your time!
    ED

  22. Ed,

    Mortar platoon leader and later company commander of Combat Support Company, 2nd Battalion, 81st Armor, 1st Armored Division, Erlangen, Germany, 1974-1977.

    You hadn’t mentioned the caliber of your rifle before, so I couldn’t be specific, but now that I know, also get some 10.2-grain JSB Exact pellets. I think among all of those I have mentioned this spiraling tendency will go away.

    As for the dispersion, I have actually watched spiraling pellets out to 50 yards and they don’t disperse all the time. Sometimes they just rotate around a center at the same distance all the way. Other times they do disperse. You should be able to put a target at 18 yards and predict where it will be hit, based on the other targets.

    B.B.

  23. Hi B.B.:
    Follow up to our last. I ordered a box of Crosman Premiers 7.9 (JSB were on back order) and the results are better. I set my zero at 12 yds and my groups at 10 yds are 1/2 low and at 20 yds 1/2 high, but they are vertical. Need to see how the group does at longer distances. Semper Fi!

  24. i know this dont really go with this forum but i got a beeman rs2 sportsman series break barrel for christmas.when i took it out i mounted the scope and sighted it in at 15 yards,but it was shooting 2 in. groups?so i started playing wit it and after about 200 rounds i was hitting pepsi bottles at 85 yards aiming at the top of the bottle and my groups improved at 20 yards i was hitting the same hole.after about 600 rounds i oiled it and was shooting fine for 50 or so rounds and then it just started goin crazy. i went from shooting half inch 3 shot groups at 15 yd. to 3 in. groups using same pellet (crosman premiers)at same distance and its getting aggravating,please help!

  25. I think I know what’s wrong. You are shooting Crosman Premiers, which are wonderfully accurate, BUT, they do lead the barrel.

    Here is what I want you to do. I want you to clean your barrel. I really want you to use a new brass brush loaded with JB Non-Embedding Bore Cleaning Compound. Please read this report and clean your gun exactly as I describe there:

    /blog/2005/11/is-your-airgun-barrel-really-clean/

    I have talked hundreds of shooters through a similar problem and I’m pretty sure it will work for you. You can buy the JB compound at a good gun store if you want to speed up the process. Don’t use Hoppes No. 9 or any other solvent cleaners — only use JB paste that most benchrest shooter clean their barrels with.

    Then get back to me on the current day’s blog (whenever that is) and tell me your results. I will then tell you how to continue to keep shooting the same pellets and not have to clean the barrel again.

    /blog//

    B.B.

  26. Anonymous,

    Great news that your barrel cleaning improved accuracy!

    Please join us on the daily (active) blog with other airgunners that are sharing great information.

    Here is a link to take you to current/active dialogue:

    /blog//

    Look forward to hearing from you.

    kevin

  27. B.B.

    I’m a 34yr old pilot that hasn’t fired a rifle down range since my 10th grade JROTC class. I recently purchased a Crosman Quest 1000 to take me back to the happy place I recall the range was for me. Many things you talked about helped me thru the 1st 50rds I’ve fire, is their any advice for do’s and don’ts with my new rifle.

    Thanks,
    Wings.

  28. Hi Wings,

    Welcome to the wonderful world of air guns. You posted to a blog that was written in 2005. Come join us at /blog/ and ask your question on our current blog.

    There’s a group of folks there that will be happy to answer your questions.

    Mr B.

  29. Tom am I missing something? It seems to me that the separation distance between bore and scope has to come into play here. For example on my condor with rings and a tri-rail there’s quite a gap there, meaning I have to point the scope looking more down to get on-sight at 20 yards. With that much of an “X” (the difference of the scope looking down, or the bore pointing up) and assuming 950 fps using 21.1 Gr. .22 Cal. Beeman Kodiaks. Do I still want to use 20 yards? I’m looking for no more than 1/2 an inch above line of sight. Thanks From SavageSam

  30. SavageSam,

    Keep the 20 yards! It’s too handy not to use.

    The scope separation will THEN affect where the SECOND impact point is – and that you determine on the range.

    In other words, don’t think about it too much. But if you DON’T use the 20 yards with normal velocities (800-950 f.p.s.) you will have a screwy setup.

    B.B.

  31. I think this discussion is all about scope on a rifle which is at least 1 inch above .
    If I use default factory open sight , do I still need to follow this sight-in procedure ?
    thanks !

  32. Here is an easy way to understand this problem and to answer your question with any gun. If you put a target against the muzzle and sighted on the same target with the sight, where would you hit, relative to where the sights are looking?

    You would hit below the point of aim, of course.

    The discussion in this report is the range at which you want the aim point and the impact point to coincide. And it works for open sights as well as scopes.

    As you point out, scopes will always be higher than open sights, but both are higher than the bore.

    B.B.

  33. Hi I just purchased a Gamo Shadow 1000 RSV, .177 air rifle. It looks, feels and performs in my humble and inexperienced opinion beautifully. When I use an H & N Silverpoint pellet at 10 yards the point of impact is 1 inch above center. When I use an H & N Excite Econ hits are about 3/4 inch up, firing horizontally. Using latter pellet when I shoot downward at 10 yards it hits almost the center point. What in your opinion will be the drop at say 100 yards. Thank you. GTC

  34. GTC,

    I would guess that it will drop something between 6 and 12 feet at 100 yards.

    This blog is extremely old. Why don't you come to our current blog, where you will be with thousands of other readers, some of whom may know the answers to your questions?

    /blog//

    B.B.

  35. I am shooting a Diana Model 36 with Beeman Model 1222 Pellets. I am super confused because I zeroed at 25 yrds, I then shot at 50 yards, expecting a drop, when I checked my target I was hitting almost 7 inches high. How is this possible? Sorry, I’m a major air gun novice, and was unable to glean the answer to my question from the previous posts. Any help would be much appreciated. Thank you.

    -ES

    • ES,

      Welcome to the blog!

      It’s impossible for me to say what is going on with the information you provided. A scope cannot normally be zeroed for just one distance, so I would need to know a lot more about the zero before trying to answer your question.

      The bottom line is, your scope is zeroed for 25 yards and for one other distance that we don’t know yet.

      I had to really search for what a Beeman 1222 pellet is. Please refer to them by their product names in the future. The model 1222 is a Chinese-made lightweight hollowpoint. That is probably the root of the problem, but as I have never tested them, I can’t really say. Most Chinese-bmade pellets are very unstable, but there are a few, like the ones made by Qiang Yuan, that are exceptionally good.

      For shooting a .177-caliber Diana 34 at 50 yards I would think a good JSB Exact pellet would be best. At least we would expect it to be stable.

      I’m not trying to be snotty (sounds like it, though) but that’s the best I can do with the information you provided.

      B.B.

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