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  #1  
Old 05-28-2010, 03:06 PM
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zeroing in at 25 yards


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i have been told that when i sight my rifles (308 win and 30-06 sprfld.)in to dead on the bullseye at the 25 yard range that my rifles will be dead on at 100 yards ..is this a true statement.. we were discussing how to sight in my rifles and not using so many rounds to do it.. then he said after the 100 yard sight-in is completed ,,i could go up 6 to 8 clicks (1/4 @100 yards on the turrents)and be on target at 200 yard s..what do y'all think about this..is he full of hog-wash.
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Old 05-28-2010, 03:23 PM
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It can be done with most calibers/chamberings but you have to know certain variables before you can complete the zeroing. You need to know the sight line axis above the barrel axis. Trajectory of the round your working with and then some fairly simple math calculations to determine the correct height. Easier way is to have your rifle zeroed at whatever range you want then place targets at the intervening range, shot and record the difference in height. Most can be roughly done using 1.5" below point of aim at 25 yards with final check at 100 yards. It will be rough but get you on paper at 100 yards for final zeroing.

You definately need too know your rounds trajectory to make the 200 yard sight adjustment. There are tables that will tell you that information in many of the reloading manuals. Need bullet weight, ballistic coefficient of bullet, zero range and bullet velocity at muzzle. With that information look it up in various tables from the manuals.
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Old 05-28-2010, 03:23 PM
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There are other variables too. Scope above center height, velosity, bullet B.C.etc. You can can plug in these into a program such as the Hornady site and get a general idea. This will give you a good starting point, but always test in the field. I have tried this many times and I always must fine tune at the range 200 yd.,300yd.
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Old 05-28-2010, 04:16 PM
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My experience is that most scoped rifles will shoot high at 100 yards if zeroed at 25.

I prefer to bore sight at 50, move to 100, then zero at 150 or 200 depending on caliper.
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Old 05-28-2010, 05:25 PM
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A typically-scoped centerfire zeroed dead-on at 25 yards will shoot 2 to 3" or so high at 100 yards. This will put things dead-on again at somewhere around 225. There are many variables, however, the chief being the exact height of the sight line above the bore line. It is a useful rule of thumb to know for sighting a rifle as it can save you a lot of ammo (and frustration) just getting on the paper at 100 yards, but ALWAYS verify the zero at at least 100 yards before taking the rifle out to hunt.
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Old 05-28-2010, 05:51 PM
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Pisgah nailed it...zero at 25 yards with most modern centerfire rifles, of small to medium bore, and with a muzzle velocity of 2700fps, or more, and you'll be 2 to 3" high at 100 yards. Finish by dialing in at 100 or 200, or whatever range you prefer, but it's best to keep your groups around 3" high at 100.
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  #7  
Old 05-28-2010, 07:04 PM
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You'd best try it. It will be close at 100 but you never know. Shoot some paper to be sure.
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  #8  
Old 05-28-2010, 07:32 PM
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pisgah hit it right on....now, there can be a problem and you should check your zero at 100 and then 200 yds, and maybe even farther. The deal is that if you don't hit EXACTLY where you are aiming, then that throws the whol trajectory table way off. If you are 1/2" off, man, you will be way off.
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  #9  
Old 05-29-2010, 04:05 AM
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Quote:
Originally Posted by RaySendero View Post
My experience is that most scoped rifles will shoot high at 100 yards if zeroed at 25.

I prefer to bore sight at 50, move to 100, then zero at 150 or 200 depending on caliper.
True! Usually about 3 1/2" high @ 100 yards. I first boresight my rifles then fire no less than 5-shots @ 50 yard targets. Then proceed to sight-in @ 100 yards to where the 5-shot grouping is 1.5" high depending on which caliber I am sighting in.
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  #10  
Old 05-29-2010, 08:19 AM
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Excellent advice from many here. Dead center at 25 yards with most modern centerfire cartridges will indeed put you roughly 3" high at 100 yards. I've used this method for years.

I'd also like to suggest that you consider getting a book or two about rifles by Jack O'Connor. "The Complete Book of Rifles and Shotguns" and "The Hunting Rifle" are packed with excellent advice and information by a man who knew what he was talking about. The information is as valid today as it was when it was written many years ago. O'Connor's style will not bore you!

Go here: http://www.abebooks.com/

Type in "O'Connor" for author and "Rifle" for key word. You'll find both books for less than $10 each
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  #11  
Old 05-29-2010, 11:00 AM
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Just a word about adding clicks for long range hunting shots -- I don't do it, ever. The reason is simple -- adjustment mechanisms are the primary things that can go wrong on any scope, even the highest-quality, most-expensive ones, and changing settings constantly is just asking for needless, accumulating wear. Except for situations where you're shooting at teeny-tiny targets at very long ranges (like plinking at 500-yard prairie dogs) it's just not needed. A mid-bore centerfire (think .30-06 or .270, say), zeroed 3" high at 100 yards, will plunk a bullet right in to the vtals of a hooved critter out to 400+ yards while you're still "holding on hair", as a friend of mine likes to say.
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  #12  
Old 05-29-2010, 02:59 PM
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[quote=RaySendero;508888]My experience is that most scoped rifles will shoot high at 100 yards if zeroed at 25.
quote]


Yup. Sighting in at 25 will get you on the paper @100. Make adjustments for zero and shoot again at 25 to know where you wanna be in the future.
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  #13  
Old 05-30-2010, 07:09 AM
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Everything depends on your expectations. Trajectory is either calculater or observed, but observation is always required. Ballistics programs are available (some free), or calculate yourself. For rifles, zero @25, is on the paper at no more than +3 @100, and if your target no more than 100 yards, & that meets your expectations, then go no further.

If not, then know your trajectories. If target shooting, exactness is important. If hunting, Point Blank Range (PBR) is important. PBR is decided by you, and is calculated based on the kill zone for your quarry. Example: kill zone for a moose might be 16 in. dia., but for a white tale deer it might be 8.

PBR has little relevance if 100 yds is tops, but if you might shoot at 150, 175, 200, ..., then its no longer just "nice to know". Ballistics programs reveal ball-park details, and range time refines it for your specific rifle & ammo.

In my case, I make trajectory printouts for each, and use them to know my capabilities. Follow-on range time gives confirmations, or reveals changes that must be understood & applied.

I enjoy my 7mmRM, .45-70, & 5.45x39. With a 4" PBR, my 5.45x39 has a max PBR of 248yds., dead-on @212, 6.5 low @300, -.25 @25yds, & +2 @100. If I shoot @300, then I'd better hold-over 2.5 in., or I miss the kill zone or lose the match. For my 7mmRM max PBR is 236, dead-on @202, -8 @300, 0 @25, & +2 @100. For my .45-70 max PBR is 131, dead-on @112, +.6 @25, +2 @75, +1 @100, & -11 @175. Note: All numbers change if I choose a different kill zone.

All of the above comply with zero @25, and no more than +3 @100, but there's a lot going on in between and after 100 that's critical to either target shooting or hunting.
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  #14  
Old 05-30-2010, 07:48 AM
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Quote:
Originally Posted by RaySendero View Post
My experience is that most scoped rifles will shoot high at 100 yards if zeroed at 25.

I prefer to bore sight at 50, move to 100, then zero at 150 or 200 depending on caliper.
My experience exactly.

I'm fortunate enough to have a 4' X 6' picture window that looks straight at my backyard archery target 75ydzs from the kitchen table. I set up my bag rests, and eyeball bore sight from there. I'm rarely off by more than half a target face at 100yds.
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  #15  
Old 05-30-2010, 07:31 PM
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Originally Posted by TMan View Post
My experience exactly.

I'm fortunate enough to have a 4' X 6' picture window that looks straight at my backyard archery target 75ydzs from the kitchen table. I set up my bag rests, and eyeball bore sight from there. I'm rarely off by more than half a target face at 100yds.
TMan,

I think the crux of the "zero-at-25-yards" logic has always been that it will completely avoid the chance of being "...off by more than half a target face". A 2'x2' target, at 25 yards, is impossible to miss, unless your gun or scope is seriously out of whack. Firing one or two shots at this distance, adjusting to zero at 25, then checking at some greater distance is a 100% fool-proof method, for modern center-fire cartridges. If you have not tried it, the simplicity of the approach and guaranteed results will quickly make a believer out of you.

Another great advantage to this is you never wind up trying to find that one hole in the 100 yard target, after using the bore-sighting technique: When your target is at 25 yards, you can usually see exactly where you hit through your scope, and often with the naked eye! It's faster, simpler and you almost have to try in order for it to not work. Besides...Jack O'Connor was a proponent of the 25-yard sight-in method, so it MUST be the best!
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  #16  
Old 06-01-2010, 05:36 AM
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Yup, that's the way we've always done it... after bore-sighting, make sure you're on or really close at 25yds and then that makes sure you're on the paper at 100yds for the actual zeroing. That way you don't start out at 100yds and miss the paper and have no idea which way to adjust it.
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  #17  
Old 06-01-2010, 05:59 PM
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TMan,,you did'nt happen to have that planned out when you told the wife ''' we need a new window here ''' hahaha lol..neat idea even if you did'nt happen to get it that way..anyway ,thanks for the idea..just think man,,my wife is wanting a picture window put in..lol
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  #18  
Old 06-02-2010, 05:10 AM
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Zeroing at 25 yards has two virtues: it saves ammo and it will get you "on paper" at 100 yards. Beyond that it is an unreliable measure of down range trajectory. I subscribe to the firm belief that you never know where the bullet will hit at any given range until you have shot it on paper, from hunting positions (not from benchrest) at that range. Computer generated trajectory tables are helpful but only in a general sense.

For the great majority of non-magnum, centerfire cartridges in scoped rifles from .243 through .35 caliber, sighting in 2" high at 100 yards will give a usable trajectory for hunting big game out to around 225 - 250 yards without hold over or hold under. Just take a manufacturer's table of factory ammo and study it. Sure, there will be some differences but how close can you hold your shots at 200+ yards? For most of us the human error beyond 150 yards is much greater than the half inch or so of trajectory difference.

Speaking as a Wyoming antelope, deer, and elk hunter (target games and varmints are a different matter), I keep all scoped centerfires sighted +2" at 100 (6.5X55, 280, '06, 35 Whelen, even .223) and all iron sight rifles zeroed at 100 (.30-30, 35 Rem., & .444). This gives me workable hunting and practice trajectories with all my long guns without remembering a bunch of different sight-in statistics for each one.

My scoped rifle rule: start at 25; refine to +2" @ 100; and always confirm longer trajectories by actually shooting at 200 yards. During hunting season if I can't get closer than approximately 200 yards I simply do not shoot. In the field, "always hold on hair."
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Last edited by naumann; 06-02-2010 at 05:14 AM.
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  #19  
Old 06-02-2010, 06:36 AM
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Ballistics 101

For the newer among us -- the reason this works is that our sights are above the barrel and pointed at the target. The barrel is not parallel to the line of sight; it is pointed upward. The bullet starts out an inch or two below the line of sight and crosses through it some 25 to 35 yards out and continues to climb.

Gravity continues to work on the bullet and its climbing eventually slows and stops, and the bullet's path turns gradually downward, with the downward slope increasing as it gets farther and farther from the muzzle. The high point is referred to as the mid-range trajectory height and is listed in most ballistic tables. It will vary with the barrel's angle of elevation (determined by the range at which the rifle is sighted-in).

Sighting-in at 25 yards catches the bullet near where it crosses the line of sight on the way up, and it crosses it again on the way down at sight-in range.

The bullet's trajectory curve is gentler (flatter) with higher muzzle velocity, stretching the distance between the bullet's two crossings of the line of sight. A higher ballistic coefficient (indicating a more streamlined bullet) also makes the curve gentler.

Conversely, a blunt bullet makes the curve sharper, bringing the two crossing points closer together. A lower muzzle velocity also makes the curve sharper.

This covers Ballistics 101. For advanced courses, please refer to senior faculty members Uncle Nick and Humpy.

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Old 06-03-2010, 06:50 PM
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I shoot for center of bullseye at 25 yards and expect to group 1 1/2" low and be right on at 100 yards. At 100 all I have to do is correct for windage. But that only works for one load. If I shoot 146 gr ammo the rules change since my usual load is 180 grains. Can't take Moe's assurance that it works for his Uncle Cletus and his best friend Fred. You need to get out there and put in the trigger time and find out what your load in your gun will shoot.
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