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Thread: Marksmanship Tip #2: Advanced Zeroing Techniques

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    Default Marksmanship Tip #2: Advanced Zeroing Techniques

    As part of the last marksmanship tip, "Know Your Rifle" (found here) a question was asked regarding how to select a zero distance for a rifle, and how to use that zero to make hits on targets at varying distances.

    In this installment, I will attempt to shed some light on these processes, hopefully making your next range trip, or foray into the field more productive.

    Before we get started, you have to know a few things about your rifle, the targets you hope to hit, and the expected distances you will be engaging them from.

    Most importantly, as ole Harry Callahan put it, "A man has got to know his limitations."

    What I mean by this, is it does you absolutely no good to have a zero on your rifle that is effective from 400 to 650 yards, if YOU are incapable of making a shot at that distance...

    For the sake of this discussion, we are going to use a rifle platform that many here are familiar with, the Winchester Model 70, in .300 Win Mag with 26" Barrel.

    Ammunition: Hornady 180gr SST Superformance in .300 Win Mag, which has a muzzle velocity of 3,130 fps (listed for a 24" barrel, but its close enough)

    Scope: Leupold fixed 4x scope with duplex reticule, mounted 1.5" above the bore of the rifle.

    Target: Caribou (assume for the sake of this discussion that the 'kill zone' on a caribou is 14")

    For the sake of this discussion, we are going to also assume that the shooter is well qualified to take a shot at distances beyond 300yds, and is confident in his/her abilities to make a critical hit on this target, at 500yds.

    Now, based on past forays into the field, our shooter knows that from his pre-selected vantage point, the herd of caribou will be from 300-500 yards away. Moving closer is made difficult because of terrain issues, so it would be best if the shot could be taken at this distance.


    We've identified some of our need-to-know information:
    Rifle platform
    Ammunition- bullet weight & muzzle velocity
    Scope mounting height (measured from center of bore to center of scope)
    Kill zone of our target
    Expected distance to target

    Now, we need to get familiar with the ballistics of our round; specifically, how much the bullet drops at varying distances. For this, we are going to use a ballistics calculator, such as the one found here: http://www.biggameinfo.com/index.asp...=/balcalc.ascx

    The calculator is going to ask you some specific information, and will spit out a ballistics table based on your inputs. I have used the following inputs for the information used:
    Bullet diameter: .308" Muzzle Velocity: 3130 fps Ballistic Coefficient: .480
    Zero Range: 100 yards Range interval: 10 yards Max Range: 500 yards.
    (bullet information provided on the Hornady website)

    Go ahead and plug in the above information, at the calculator given above, so you can follow along.



    Now that you've got that massive table in front of you, what to do with it?

    The two important columns that you need to look at are the first two- Range (yards) and Path (Inches).
    Range is self-explanatory. Path, perhaps not so much.

    A negative number means that your bullet impact would be below your aiming point.
    A positive number means that it would impact above your aiming point, both measured in inches.


    Now, lets look at the drop information for ranges 300 through 500:
    300 = -9.8"
    350 = -15.4"
    400 = -22.4"
    450 = -29.1"
    500 = -41.1"

    What's this information telling us? Well, if we zeroed our rifle at 100 yards, and took a shot with it at 300 yards, our bullet would strike 9.8" below the center of our target, which would put it outside of our kill zone- (a 14" kill zone would be 7" above to 7" below) So we know that we can't zero the rifle at 100 yards and make a responsible shot on our target. Further, we know that from 300 to 500, our bullet drops a total of 31.3" (41.1 - 9.8 = 31.1") This tells us that we are not going to find a zero that will be perfect for every shot from 300 to 500 yards. However, we're not done, and I'm sure we can get a pretty good zero to work from.

    Lets adjust that zero range to something more practical, right in the middle of our expected range- 400 yards. Now lets look at the table:
    300 = 7.0"
    350 = 4.2"
    400 = 0.0"
    450 = -5.8"
    500 = -13.2"

    That's got us right where we want to be! Take a dead-on aim at 300, and you will hit the upper portion of the kill zone. Aim dead on at 400, and you hit right where you're aiming. At 450, your bullet will impact about 6" low. A shot at 500 (the limits of our shooters ability) will be outside the kill zone. This means that all but the furthest Caribou are fair game.

    To make a better shot, (one more centered in the kill zone) our shooter would aim a little low on shots nearer than 400 yards, and aim a little bit high on shots further than 400.


    Now, we've determined that the rifle should be zeroed for 400 yards, for this particular hunt. He needs to zero his rifle for 400 yards, but only has a 100 and 400 yard range to work on... How can he zero his rifle, without spending GOBS of time, and hundreds of dollars in ammunition?

    EASY!

    Taking a look back at the ballistics calculator with the rifle zeroed at 400 yards, look at the 100 yard path. It says that our bullet would impact 5.6" above our aim point, when zeroed at 400 yards... Our hunter *has* a 100 yard range... He can zero his rifle at 100 yards, but instead of knocking out the center of his target, he wants his group to be centered 5.6" above the center... Once he's done that, his rifle is (nearly) zeroed for 400 yards, and he can walk the rifle to the 400 yard line, and expect to at least be on paper at that distance, which will allow him to fine-tune his actual zero.

    Point of note: I do not advocate taking a rifle into the field that has been 'zeroed' with an adjusted 100yd zero. At best, this type of zero should be used to get you 'on paper' at the actual distance you would like to use. Barrel differences, elevation differences, temperature, and all sorts of other factors come into play, and you certainly don't want to be wounding an animal.

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    Just to help folks connect the dots.. these and other tips when Appleseed comes to Chugiak end of July!
    http://forums.outdoorsdirectory.com/...ming-to-Alaska
    Thank you, Project Appleseed!

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    Do we really need these posts here? Has anyone asked the question? No. These postings should be made on Appleseed's website, not here.

    And by the way,

    "Point of note: I do not advocate taking a rifle into the field that has been 'zeroed' with an adjusted 100yd zero. At best, this type of zero should be used to get you 'on paper' at the actual distance you would like to use. Barrel differences, elevation differences, temperature, and all sorts of other factors come into play, and you certainly don't want to be wounding an animal."

    So, you don't advocate wounding an animal, but your example has someone taking shots at 300-500 yards on a caribou with a 4X scope with a 100 yard zero over 5 inches high?

    Post this stuff on some other forum.

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    I, for one, am aware of the above marksmanship information and have been so for 30+ years (the credit for this goes to my military instructors, my friends, and fellow military shooters). I don't mind reading a friendly reminder from time to time even if I've mastered the concepts. I'm not familiar with Appleseed's website so I'd have never seen this information had it not been placed in this great forum. I really enjoy the threads and the posts in AOD and even if I don't need the information. I imagine there's someone out there, maybe a new hunter or shooter, that just read this and said "I didn't know that". Everyone starts somewhere. Just sayin's all....

    Happy Memorial Day to each and every one of you!

    MyTime

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    Quote Originally Posted by GD Yankee View Post
    Do we really need these posts here? Has anyone asked the question?
    Actually, yes; a member on this board specifically asked the question in my previous post, which is the reason for this topic. Should you already be familiar with the concept of near/far zeroing, great. If not, please re-read the post, as your comprehension of it seems to be 'off'. Whether that is because of my literary skill, or an unwillingness to learn on your part, I cannot be sure.


    Point of note: I do not advocate taking a rifle into the field that has been 'zeroed' with an adjusted 100yd zero. At best, this type of zero should be used to get you 'on paper' at the actual distance you would like to use. Barrel differences, elevation differences, temperature, and all sorts of other factors come into play, and you certainly don't want to be wounding an animal.
    So, you don't advocate wounding an animal, but your example has someone taking shots at 300-500 yards on a caribou with a 4X scope with a 100 yard zero over 5 inches high?
    This is why I question your comprehension of what was written- specifically the section you quoted. Read it again, please.

    The modified 100 yard zero (5.5" high @ 100 yds) is used to allow the shooter to be 'on target backer' at 400; this will allow the shooter to establish a proper 400 yard zero relatively easily. I in no way shape or form advocate someone using a modified 100yd zero to take a shot on game at distance.

    Incidentally, you appear to be incredulous that a shot like this should even be attempted with a 4x scope; would it assuage your sensibilities if an 8x scope were used? What about a 12x scope? Would it horrify you to know that shots at distances greater than this, on targets smaller than this, have been done repeatedly, without the use of a scope at all?

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    Quote Originally Posted by Project Appleseed View Post
    Would it horrify you to know that shots at distances greater than this, on targets smaller than this, have been done repeatedly, without the use of a scope at all?
    Just to relive old memories...
    1980-1984
    19-23 years old
    USMC
    500 Meters
    Known Distance Course
    M61A1
    55 grain FMJ
    Prone position
    Iron sights, no scope or optics of any sort
    ...every round hit within a 10 inch spread, in the center area, every time I fired during those years.

    It can be done. Can I do it again now? Heck no, the eye balls won't let me. Leupold, Vortex, and others have become my friends to make up for aging eyes.

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    The ballistic information is somewhat useful in that given hypothetical situation but doesn't take into account the variable of the combinations accuracy. If the rifle, ammo and shooter, shoots 1 moa the room for error shrinks by quite a bit, you no longer have the whole 14" to play with.

    Gus

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    Quote Originally Posted by GD Yankee View Post
    Do we really need these posts here? Has anyone asked the question? No. These postings should be made on Appleseed's website, not here.

    And by the way,

    "Point of note: I do not advocate taking a rifle into the field that has been 'zeroed' with an adjusted 100yd zero. At best, this type of zero should be used to get you 'on paper' at the actual distance you would like to use. Barrel differences, elevation differences, temperature, and all sorts of other factors come into play, and you certainly don't want to be wounding an animal."

    So, you don't advocate wounding an animal, but your example has someone taking shots at 300-500 yards on a caribou with a 4X scope with a 100 yard zero over 5 inches high?

    Post this stuff on some other forum.
    GD,

    I don't have any problem with it.
    Look, if you're not interested in a discussion that you happened to eavesdrop on, then why comment at all? I think most folks if they overheard a conversation that didn't interest them, would just move on.

    Appleseed's previous post (http://forums.outdoorsdirectory.com/...ight=appleseed), was posted in the Shooting forum, which seemed appropriate. To me, the post seemed well-received by those who commented. I suppose those who didn't need or want the information, just moved on.

    I think MyTime said it well, and it's true in general that members generally post information in good spirit, meaning well and hoping to contribute iinformation that might be useful to some others. That's been the best of AOD/OSA fireside chat type discussions IMO. No one needs to ask a question or invite these contributions. They're voluntary contributions made in good spirit. Let's keep it that way, shall we?

    Best wishes in the season ahead, man

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    Use a 32 special with open sights, and hold at the top of the trees for 500 yard shots......half way up for shots at 400, and hold at the top of the antlers for 300, for 200, hold at the top of the back.


    Get 'er done!

    Thanks for the post.


    I made 3, 450 yard shots with my 32 special, all in a 15 inch circle. I wouldn't hunt at that range, and all the calculations have it sighted in for 150, with 36 inches of drop at 400 yards, my 32 was sighted in for 100....so I was guessing a little....
    Eccleasties 8:11 Because the sentence against an evil deed is not executed quickly, There for the hearts of the sons of men among them are given fully to do evil.

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    Do we really need these posts here? Has anyone asked the question? No. These postings should be made on Appleseed's website, not here
    Agree with GD Yankee 100% on this one!

    Sure the ballistic theory here is semi sound.

    But, I am going to say a 400 yard zero on a hunting rifle with a 4x optic, 300 win mag or not is a very poor choice, and terrible information to be passing on a web site with many new hunters looking to learn from these pages.

    4x is relatively low power, at 400 yards your precision at 4x is marginal at best. Bad advice = wounded game and wasted opportunities. when you start talking 400 and 500 yd shots wind becomes an issue, in Alaska on the tundra where your hypothetical caribou hunt takes place 20-30 knots of gusting wind is very common, that's a miss or a gut shot. When you gut shoot an animal and it runs off for a slow death don't forget to punch that tag.

    Point of note: I do not advocate taking a rifle into the field that has been 'zeroed' with an adjusted 100yd zero. At best, this type of zero should be used to get you 'on paper' at the actual distance you would like to use. Barrel differences, elevation differences, temperature, and all sorts of other factors come into play, and you certainly don't want to be wounding an animal
    Hunting situations definitely call for flexibility in you and your gear. You never know if that shot will be at 25yds or 300yds. I would argue that a suitable big game rifle and optic zeroed at 100yds, and worked out to YOUR (insert Harry Callahan here) max effective range will be much more precise for all practical purposes. If you go to the range regularly and practice field shooting positions at a 6-8" target at varying ranges you will learn that limit quickly. If it is 300yds proned out, than that is where you need to get to, this is where the hunter comes into play. Any hunter worth his salt should know, or should learn how to get into position for a shot he knows he can make. I would call that hunters ethics.

    Shots at 400yds and beyond should be at paper or enemy combatants. Gut shots are ok for both.

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    Quote Originally Posted by Project Appleseed View Post
    As part of the last marksmanship tip, "Know Your Rifle" (found here) a question was asked regarding how to select a zero distance for a rifle, and how to use that zero to make hits on targets at varying distances.
    You give a ton of great info, from my knowledge all of it right and good info. Thanks.

    Your going-in supposition was that the hunter was planning a 400 yard shot; that's why I agree with all you posted.

    Me, I plan on a on 100-200 yard shot; often below that; that's why I zero at 100 yards. The few times I've shot beyond that, I hold high. That is a whole 'nother discussion of at what range to hold at the top of the animal, and at what range to hold so much above the animal.

    But that's not how you presented this. I agree with your method, and I also agree with my (different) method. To each their own.

    The one thing I'm sure we can both agree on, is practice, practice, practice! I don't enjoy seeing hunters take their first shot at long distances at a live target, instead of at paper. I'm betting you agree (Johnny?) Appleseed.

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    Quote Originally Posted by AKmik View Post
    But, I am going to say a 400 yard zero on a hunting rifle with a 4x optic, 300 win mag or not is a very poor choice, and terrible information to be passing on a web site with many new hunters looking to learn from these pages.

    4x is relatively low power, at 400 yards your precision at 4x is marginal at best.
    I agree that 400 yards is too far for many to shoot, but using 4X magnification is not the issue. Small targets may require more Xs for target definition at longer ranges, but big game hunting accuracy does not require more Xs for 400 yard shooting. YMMV.
    Foolishness is a moral category, not an intellectual one.

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    Quote Originally Posted by AKmik View Post
    Agree with GD Yankee 100% on this one!

    Sure the ballistic theory here is semi sound.

    But, I am going to say a 400 yard zero on a hunting rifle with a 4x optic, 300 win mag or not is a very poor choice, and terrible information to be passing on a web site with many new hunters looking to learn from these pages.

    4x is relatively low power, at 400 yards your precision at 4x is marginal at best. Bad advice = wounded game and wasted opportunities. .....
    ....
    Shots at 400yds and beyond should be at paper or enemy combatants. Gut shots are ok for both.
    I'm new to this forum but I'm really surprised at some of the reaction to an offer of sound information! Who rejects education? We're worried that a newbie hunter might read this and get the wrong idea? If a newbie hunter made a study of this information, applied it on the practice range, and went into the field armed with this knowledge.. how are we worse off? I'd venture to say if a newbie hunter had some of this advanced theory in his "bag" he'd be a real asset to the sporting community.

    I'm not boasting but just as an example that I can personally attest to, I was regularly taking shots on Caribou at at least 300yds and found it so within my comfort zone that I starting taking only head shots (to drop the animal instantly and waste no meat). This I was able to do consistently, under field conditions, with Aleutian winds.
    It was never necessary to take any shots further than that but it seems obvious that I ethically could have. I'm NOT a veteran hunter by most people's standards but I have taken information, like was presented here, into practice. I have practiced out to ranges well over *gasp* 500yds!

    No call for ethical 400-500yd shots? I disagree. Back to our newbie hunter, let's imagine he's taking his first shot on a Caribou. He's jittery and his shot placement is poor, or the animal is tough, or the bullet fails to perform, or... The wounded Caribou runs through rolling ground before pausing on a crest a 475yds yards out.
    Newbie hunter A) slings lead, prolifically and ineffectively. Wounded Caribou gets away and is eaten by wolves. B) gives futile chase, trying to gain that magic "less-than-300yds" that he can work within. Wounded Caribou gets away and is eaten by wolves. C) read a little something on AOD that he took to heart and put into practice. He takes a steady rest, makes his calculations, and drops the wounded Caribou right there. Wolves live happily on mice like in that movie.

    Ultimately it seems, and I can't think of any gentle way of putting it, ignorant to scorn information.

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    4x is enough magnification to kill game out as far as anyone should be shooting at said game. Bone up a bit on scope reticle subtension versus your 8" plate size and determine how far away you can sight on it.

    But, regarding the original post - is Appleseed a paid contributor to the site?

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    First, I think this information is great and I welcome it personally.
    Second, I think people are missing the point that this was just an example that Appleseed writes about and a great example at that. Some people are very capable at shooting at these distances and this figure will help them out. Change the caliber or scope power to your liking if you need to get the best of it and If this isn't for you then read a different post but please don't dog a guy who is giving the people that want it good free information.

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    How could a person be capable of making these shots if they heretofore did not have this information?

    Quote Originally Posted by alaskabliss View Post
    First, I think this information is great and I welcome it personally.
    Second, I think people are missing the point that this was just an example that Appleseed writes about and a great example at that. Some people are very capable at shooting at these distances and this figure will help them out. Change the caliber or scope power to your liking if you need to get the best of it and If this isn't for you then read a different post but please don't dog a guy who is giving the people that want it good free information.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Also just wondering if the author gives consideration to M.O. distance and value? And where to hold for the 250 yard shot.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Quote Originally Posted by Murphy View Post
    How could a person be capable of making these shots if they heretofore did not have this information?
    The best way to gain familiarity and skill in any endeavor is to practice. The techniques required to make hits at medium distances (to 500 yards or so) are fairly simple, if not easy to master.

    A person could be capable of making shots in excess of 400 yards, but not know how to use a ballistics table to establish/change their rifles zero.

    How many times have you seen someone at the range, taking aim at a rock or the berm, and 'walk the bullet in', adjusting their sights as they go? These are the folks that would be best served by the information presented above, as it reduces the time spent on the range zeroing the rifle. Additionally, the information above introduces them to the concept of bullet trajectory, and how a rifle's zero affects how their bullet behaves at distances greater than and less than, their initial zero.

    For evidence of this, look at the bullet drop from 300-500 yards in the first example- a 100 yard zero. Total drop from 300 to 500 is 31.1"; yet, when we re-zero the rifle for 400 yards, total drop from 300 to 500 becomes a scant 20.2" - that's a 1/3 reduction in drop! This is because by zeroing for the further distance, we are dramatically changing the 'angle of departure' of our bullet; & this has a significant effect on our trajectory.

    Becoming familiar with ballistics tables, how to use them, and how to determine the appropriate zero for your rifle, should be part of *every* shooters toolkit. Not because it will make you more effective at ranges beyond your current capabilities; it won't. But if/when your skills improve to the point where you can utilize this information, it will make your task that much easier.

    Also just wondering if the author gives consideration to M.O. distance and value?
    Sorry Murphy, can't put my finger on what your referring to with "M.O. Distance/Value". Please elaborate.

    And where to hold for the 250 yard shot.
    If one looks at the ballistics table used to get the 400 yard zero information, we find that the bullet, at 250 yards, will be 8.5" above our point of aim, when zeroed for 400. One could simply hold LOW 8.5", or dial-in the appropriate change on their scope (the ballistics table advises a change of -13 clicks, assuming a 1/4 MOA click adjustment)

    Hold-offs are something that one should practice at the range, not on game animals. Become proficient with gauging distances and their respective hold-offs from your zero before using them 'in real life'. Failure to do so may end up as a clean miss, or worse.

    If time/circumstances allow, I always advocate making the appropriate sight adjustment- that way you are using a consistent aiming point. (the center of your reticule)

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    Quote Originally Posted by Project Appleseed View Post
    T
    Sorry Murphy, can't put my finger on what your referring to with "M.O. Distance/Value". Please elaborate.
    Maximum Ordinate. The highest point above the line of sight to which a bullet will reach over the course of a measured or specified distance of travel.

    To be simple.....To sight a rifle in at 300 yards it might be 3" high at the normal sight in range of 100 yards. The bullet will be about 4.5" high at about 225 to 235 yards (M.O.), then will begin its decent back to the line of sight. Just an example, don't get caught up in the numbers. M. O. range = Distance to highest point. M.O. value = xx.x inches, at that distance.

    And your excellent tutoring is wasted on me as I am well versed and accomplished and have many loooong shots to my credit. I am Distinguished rifle and hold records and several close seconds out to 1600 yards.

    I just wanted the readers to be aware of the full path of the bullet as I've had students who believe the highest point above L of S is the mid range trajectory.....not so.

    And to expand on your 250 yard scope adjustment.......MOA = appx 1.04 inches @100 yards. 8.17" @250 yards is 3.4 MOA. (8.5" /2.5 {ratio of 100 to 250 yards} = 3.27 MOA) 3.27 MOA * 4 (4 clicks equal one MOA) = 13.08 clicks.

    Just one way of doing the math.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Murphy-

    Sent you an email through the board; could you confirm whether it was sent/received?

    Thanks!

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