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Old 06-11-2017, 12:07 PM
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Default Why I use a 100 yard zero.

I posted this in another thread, but I think it deserves its own thread. This is intended for as broad an audience as I can hit so, I'm including some basics on trajectory.

Hitting your target is all about understanding the trajectory of the bullet. Trajectory is the path the bullet follows toward the target.

Since gravity works, the bullet doesn't travel in a straight line.
Because the sights are higher than the bore, the barrel will need to be angled up a little in order to hit the same point you're looking at.
Because the barrel is elevated in relation to the line of sight, and because the bullet travels in an arc, there are two points of convergence where the line of sight and the path of the bullet are the same. Look at this picture:


Line of sight is referred to as Point-Of-Aim (POA).
Where the bullet impacts the target is Point-Of-Impact (POI).
So, a simpler way to state it is POA=POI at two points along the trajectory. This is true with every distance you zero at unless you zero at the apex of the trajectory.

Now let's do some real math. Here is an example of zeroing at 50 yards. With a normal AR and a sight height over bore of approximately 2.5", this is what the trajectory will look like:

Notice that at 50 yards and ~235 yards the bullet path crosses 0. This means POA=POI at those two points. The problem with this is everything between 50 and 235 will hit higher than POA. That means you'd have to hold under for those ranges. Everything closer than 50 and further than 235 will hit lower than POA. This means you'd have to hold over for those ranges. I know it's only 2" either way, but that translates to a 4" spread and some are high and some are low.

Change that to a zero at 100 yards and we get this:

Notice that there is only one place where POA=POI in this chart; 100 yards. Also notice that from 0 to ~205 the POI will be anywhere from 2.5" low to 0. This means that at any distance other than 100 yards, you'd have to hold over a little. At no time will you ever have to hold under. This simplifies the aiming from 0-200 yards because you know your round will hit within 0-2.5" low. That's only a 2.5" total spread.


So, the question comes down to, how often will you shoot beyond 200 yards? If you shoot past 200 a lot, then the 50 yard zero might be for you. If you're like me and never use an AR to shoot beyond 200 yards, and only rarely shoot beyond 100, the 100 yard zero makes more sense.

Anyway, that's why I zero at 100 yards.
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Old 06-11-2017, 12:22 PM
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Very well written and explained Rastoff. That very clearly covers a couple of aspects of the subject that I had never really considered. THANKS!
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Old 06-11-2017, 12:24 PM
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I am a fan of the 25yd zero for general use and shooting out to 400 but the 100 yard zero works great for hunting and is on my prairie dog rifle


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Old 06-11-2017, 12:44 PM
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I use a 50yd zero. It extends the point and click usefulness of my red dot vs 100yd zero. For my use, agonizing over an inch or two above line of sight at shorter distances isn't a good trade for exaggerated variance at distance as the chart indicates to 300yds. It's not a matter of how much I practice beyond 200yds, but rather that the equipment is set to better accommodate if needed.

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Old 06-11-2017, 01:27 PM
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I agree with a 100 yard zero with my hunting rifles and .22 rifles. Most all my shots are fairly close in the swamps.

I also think a 25, 50, and 75 yard target to be invaluable for under 100 yard shots later, maybe with each rifle one intends to hunt with.
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Old 06-11-2017, 10:00 PM
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Phil,
I find that an interesting viewpoint considering the number of times you've mentioned that you'll rarely even shoot 100 yards.
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Old 06-12-2017, 03:02 AM
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Plusses and minuses to all, but we'll thought out reasoning. I currently use a 50 yard zero for red dots, my variables have BDCs, so they are sighted in per instructions at 100 to make them work properly. My opinion is to find a trajectory that works for you and learn it backwards and forwards.

There's the 37.5 (I think)yard zero that looks promising for those that like the 50.

Thanks for posting.

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Old 06-12-2017, 06:30 AM
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Quote:
Originally Posted by Rastoff View Post
Phil,
I find that an interesting viewpoint considering the number of times you've mentioned that you'll rarely even shoot 100 yards.
You must be thinking of someone else. The below is what I have repeatedly posted. But even if I only had 100yd range to practice at my reasoning for a 50yd zero would be the same.

Quote:
Originally Posted by ChattanoogaPhil View Post
For me... I practice shooting offhand at steel targets from 50 to 200yds.

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Old 06-12-2017, 07:02 AM
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I have a Vortex Spitfire 3X, prism scope on my M&P Sport ll. The crosshairs have yardage lines out to 500, for 55 grain factory ammo. I have it dead-on at 100 yards and will eventually try it at longer distances, as soon as I can get to a 500 yard range. I wonder how close it will be. Anyone here ever tried one?
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Old 06-12-2017, 07:15 AM
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I have three AR's, two with Iron Sights and one Precision Rifle with a scope.

For the Iron Sighted AR's I have the sights set for a 50 yard zero because with my aging eyes shooting irons past 50 yards can be a bit frustrating. Yeah, I know Irons can be effective at 100 yards even for my eyes, however I just cannot shoot tight groups with irons past 50 yards.

For my Precision Rifle I have the zero set for 100 yards because with the help of Optics and a good rest I can manage to group around 1/2 inch. I'll also occasionally shoot it at 200 yards, the maximum for the range I shoot at but when I reach out that far I just dial in 10 clicks on my elevation dial.
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Old 06-12-2017, 07:31 AM
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Good post,thanks. My feeling is that no matter what distance you pick to zero you need to practice at every distance you can to know where your rifle hits and to learn range estimation which for me is hard to get right.
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Old 06-12-2017, 08:03 AM
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As a guy who fired .223 first out of a bolt action, coming to the AR platform was a real eye opening experience. The jump from 1.5" above bore to 2.5" above bore has a real effect on the trajectory. For my bolt gun I use a 50 yd zero which gives me a 150 yard coincidental zero for 50 grain V Max. For the AR I did the battle sight zero of 25 meters and was less than impressed. I rezeroed at 42 meters and found much more happiness with a second zero at 220 meters. No idea why I did the AR in meters.
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Old 06-12-2017, 08:17 AM
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Quote:
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Good post,thanks. My feeling is that no matter what distance you pick to zero you need to practice at every distance you can to know where your rifle hits and to learn range estimation which for me is hard to get right.
I use a 1x red dot on my AR. Range estimating and holdover isn't an issue-- just hold center and click. Any distance beyond what a 50yd zero would accommodate would also be beyond the expectations I have of my rifle. Point and click operation.

My rifles with magnified optics and mildot reticles I can estimate distance fairly well using objects/targets of known size. It's actually a fun practice. At the range where distances are of course known, I play around in reverse estimating the size of objects/targets. Good exercise for old brain.

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Old 06-12-2017, 08:53 AM
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I also opted for a 100 yard zero with my M&P15 TS.

The reasons, in addition to the sound discussion by Rastoff above are provided in this article by Kenan Flasowski on the Shooting Illustrated site.
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Old 06-12-2017, 10:46 AM
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(above link)

"I am a big fan of the 200-yard zero, and it is very close to a 50-yard zero. My primary AR is zeroed at 200 yards, but I like to be able to engage out to the maximum effective range of the 5.56 NATO cartridge. With a 200-yard zero, the bullet does rise above LOS, but not more than about 2 inches at 120 yards, so holdunders are negligible, and the holdovers at 25 yards and closer are similar to the 100-yard zero. But I have the luxury of unlimited access to a 400-yard range. Many armed citizens may not get to train much and may not shoot at 400 yards—ever."

I agree with Kenan Flasowskl's comments in the first part of the paragraph above, both he and I use 50yd zeros on our primary ARs . I do not agree that you must have a 400yd range to set up your rifle with a 50yd zero (or 25yd or whatever), at least that's what he seems to be implying. ARs for self defense aren't set up to accommodate practice range facilities, but rather to accommodate the purpose of the rifle if and when the need arises away from the range.

As far as the rest of the article, I think Kenan spends WAY too much time fretting about 1-2in holdovers. In self defense situations, unless the bad guy is standing perfectly motionless like paper on a target stand, and the bad guy poses no immediate threat to you so you can diddle around with precise holdovers of an inch... forget about it.

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Old 06-12-2017, 11:01 AM
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If you are a hunter you should have a range card for your rifle/ammo anyway. So the zero really doesn't matter as long as you practice with it.

It's all preference.

There is the range card on my SCAR-17. Laminated and tucked into the stock, one quick tug and I have ranges out to 800 yards with scope clicks and holdover....



a good site to make these is here:

JBM - Calculations

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Old 06-12-2017, 10:10 PM
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Quote:
Originally Posted by ChattanoogaPhil View Post
You must be thinking of someone else.
Indeed, I must have been mistaken. Not the first time, won't be the last. Even so, I would think the -2" to 0 from muzzle to 200 yards would suit you well.
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Old 06-13-2017, 09:08 AM
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I use the 100 yard zero on my battle rifles for just as you said Rastoff, pure simplicity. All you have to ever remember is how much holdover is needed, if any, for ranges from 0 to 300 yards and even greater. Bonus is my ACOG is then zero'd at the recomended yardage (because of the reticle) so everything is the same for me on all my battle/SD rifles. Simplicity.
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Old 06-13-2017, 09:52 AM
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There's nothing wrong with selecting 100 yards as the zero point, depending on the external ballistics. A high velocity round, like 5.56x45 or 7.62x51 probably better zeroed at 200 yards.

The offset between the scope and bore will shoot low at 100 yards, zeroed at 200. The closer you zero, the greater the deviation at longer range.

Slower rounds, like pistol caliber carbines, are best zeroed at 100 yards. They drop like a rainbow, and 100 yards usually gives you "deer accuracy" from 0 to 150 yards (- 7").

I use a program called "Ballistic" for iPad and iPhone for an objective estimate of external ballistics. Its tables show the deviation based on the ballistics, zero distance and offset. The software is $20 well spent.

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Old 06-13-2017, 10:37 AM
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An additional aspect bears addressing here. Some of us use different zeroing methods and techniques and we all have different skill levels. Comments are based on my experience only and I seek no argument.

I zero using a Hart pedestal rest with a Protektor sandbag and a Protektor bunny ear bag rear rest. I use handloads with a either a Sierra 69 MK or Sierra 65 GK and my observations are based on such loads rather than the 55 grain commercial loads that many shoot, though there are likely some similarities.

From the rest, I zero approximately 2" high at 100 yards for an approximate 200 yard zero. To closely simulate an actual "field" position, i.e., using less than a stable rest, I support the rifle forearm/ handguard with my left hand placed atop the forward sandbag.

This method, for me, consistently causes point of impact to be approximately 1 1/2"-2" low at 100 yards and 3"-4" low at 200. This could vary from shooter-to-shooter. The point is that it is worth checking as the variance could be significantly less or greater than what I have experienced.
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Old 06-13-2017, 09:08 PM
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Quote:
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I use a program called...$20 well spent.
Or you can use Ballistic Calculator GunData.org for free. That's where I got the pics for the OP.
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Old 06-14-2017, 01:36 AM
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I zero around a ballparked 45-50yds. Longest shot I can take on the property that is cleared is 140yds. My bullet rise isn't so much with this zero that I can't hit 3" spinners from that distance, and I'm still accurate enough at shorter distances. I don't have a battle rifle, I just shoot in my backyard for fun. That zero works for my situation. If the situation changed, I'd likely change my habits with it. Would love to be able to shoot 300yds from time to time.
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Old 06-14-2017, 07:15 AM
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Rastoff, sounds like how we trained with the M14 in the Army.
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Old 06-14-2017, 09:36 PM
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I always zero at 100 yards however most whitetail i harvest are well within that distance. Last year the buck closed the gap to within 30 yards very quickly. I was shooting from a stand 25 ' in the air. I hit him high I got him but I almost missed him. I also shot a coyote from the same stand same elevation at 70 yards. I drilled him dead on. To be honest most game I take is within 100 yards. I am thinking strongly about changing my zero to fifty. But I agree that 100 yards is a good rule of thumb. I think the farthest I have target shot was 300 yards, I received a education in how much my flat rifle drops. If I remember correctly it was about 18".
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Old 06-15-2017, 08:58 AM
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Quote:
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I think the farthest I have target shot was 300 yards, I received a education in how much my flat rifle drops. If I remember correctly it was about 18".
18" seems a little much for a 55 grain, were you shooting heavier stuff? If so, then the 18" makes a ton more sense.
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Old 06-15-2017, 09:58 AM
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What is getting lost in this discussion is that one zero is not inherently better than another but you have to know "YOUR" zero. If you use 50 then use it consistently for the same type of rifles being used for the same purpose. Know your hold over at different yardages. Study the trajectory charts so you can hit your intended target with intended accuracy. The exact same principles apply to a 100 yard zero.

What does it matter if the guy in the bay next to you is shooting a 100 yard zero if you know, train and shoot a 50? If you can make positive hits with your zero of choice and understand how it effects the flight of the bullet you are shooting what else matters? Run what works for you. If you don't know what works for you try 25, 50 and 100 and see what you prefer. One still most likely stand out as the righ zero for you based on the actually shooting you are doing.

What I like or prefer has little bearing on you unless you shoot the same gear the same way that I do with the same indented purpose. Knowing this reduces the discussion to a matter of preference vs a lesson in objective truth. IMHO
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Old 06-15-2017, 11:09 AM
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LOL I do a 25 yd zero.......... then head over to the 100yd range for my final zero....We still can't hunt with semi's in Pa. so AR's are for SHTF or S---- & Giggles........

If I recall eb07 graphs (I have a laminated set in my range bag) out to 200 everything is + or- 2 inches of POA...... my local range is 100yds and beyond 200 in SHIF I'm more likely hiding/clearing the area than engaging. If I"m bugged in I don't think I have a shot longer than 100 yds from the house.

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Old 06-18-2017, 09:28 PM
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Even though I've shot AR's for many years (casual shooting) I never thought about how to really zero my rifle other than to hit what I happened to be aiming at right then.

I started changing my thinking when I read an article in the October 2008 SWAT magazine by Lt Col Freddie Blish, USMC (Ret.) entitled "Battlesight Zero - Who Has It Right?". In this article he examined and compared the Army and Marine Corps doctrine in teaching marksmanship and BZO to their people. He also mentions in passing the 100 yard zero used by "an elite US military special operations unit...This BZO fits their particular mission profile...". He also is working with just the iron sights.

I am not even going to attempt to summarize his work, I'd probably waste space trying to do it justice and most likely fail. If you are interested you can look it up yourself. But rather I am going to jump to his conclusion.

"So which BZO is best? In my (Blish's) humble opinion, it is the 50/200 zero (using the large aperture) for most situations, However, mission, enemy, troops, and terrain often dictate particular requirements."

I have adopted this zero as being most effective for most of my shooting which is inside of these distance parameters. Those shooters who's shooting patterns mimic mine may also want to consider this zero.

Of course, those with different requirements (hunters, long-range target shooters, etc.) would be better served looking at zeros which fit their needs and are better explained by experts in these fields. As several other people in this thread have addressed.

An additional thought as I was writing this is that it would not hurt casual shooters such as myself to explore other types of shooting, especially longer ranges, in an effort to expand our knowledge of how our rifles (and ammo) perform in these areas and broaden our skills should they ever be needed.
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Old 06-19-2017, 12:51 PM
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Thanks for referencing the BZO article.

No matter what zero someone has chosen, I think everyone will find something to reinforce their zero decision or rethink it.

BATTLESIGHT ZERO (BZO): Who has it right? | Robar Guns
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Old 06-19-2017, 01:20 PM
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Thanks for referencing the BZO article.

No matter what zero someone has chosen, I think everyone will find something to reinforce their zero decision or rethink it.

BATTLESIGHT ZERO (BZO): Who has it right? | Robar Guns

Coool ........with my 100yd zero I'm in the same camp as "an elite U.S. military special operations unit"....... who would have thunk it!!!!!

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Old 06-19-2017, 01:30 PM
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Coool ........with my 100yd zero I'm in the same camp as "an elite U.S. military special operations unit"....... who would have thunk it!!!!!

You be in sync with the special operators... very cool.

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Old 06-19-2017, 02:12 PM
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You be in sync with the special operators... very cool.

Now I need to "gets me" one of those "Punisher" decals!!!

Truth is IMHO the Article, and WVSig pretty much sums it up.......1)there is no single right answer; even the Pentagon has 3....but 2) as WVSig stated you need to know the impact of whatever choice you make!!!!
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Old 06-19-2017, 03:44 PM
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Now I need to "gets me" one of those "Punisher" decals!!!

Truth is IMHO the Article... there is no single right answer; even the Pentagon has 3....but 2)... you need to know the impact of whatever choice you make!!!!
Well sure... every zero is a compromise of some sort.

The idea is to understand what you expect from your rifle and choose the compromise that "best" serves it. That the authors in both linked articles in this thread either use a 50yd zero on their personal rifle or believe it to be the "best" BZO zero and the most common with the better known shooting schools and instructors around the country... is just a coincidence they all agree with me!!!

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Old 06-20-2017, 08:21 AM
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Well sure... every zero is a compromise of some sort.

The idea is to understand what you expect from your rifle and choose the compromise that "best" serves it. That the authors in both linked articles in this thread either use a 50yd zero on their personal rifle or believe it to be the "best" BZO zero and the most common with the better known shooting schools and instructors around the country... is just a coincidence they all agree with me!!!
You and they are all still wrong.........the 100 yd zero is the way to roll!
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Old 06-20-2017, 08:30 AM
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You be in sync with the special operators... very cool.
Wonder if I can get an "In sync with Special Operators" shoulder patch....... maybe a ;dagger through a bulls eye w/ 100yds stitched underneath ?????



We've taken this thread way off the rails...........................
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Old 06-26-2017, 06:19 PM
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All this discussion about zeroing is meaningless unless one takes into account the height of the aiming instrument (iron sights, red dot, scope, etc.) above the bore axis. Using the same ammo, in the same length barrel, producing the same velocity, a 100yd sight in with a set of AR iron sights at 2.6" above the bore axis produces a vastly different set of numbers than a 100yd sight in with a set of iron sights at .9" above the bore axis.

Why? Because the angle of the barrel with higher (2.6") iron sights is different from that with lower (.9") iron sights which cants the same trajectory of the bullet along a slightly different path.

Examples - Using Handloads.com's ballistic calculator, I assumed a typical AR type rd, a .223 dia, 55grn Spitzer bullet with a BC of .259 traveling at 3000fps MV. Lets take an 18" AR with iron sights that are 2.6" above the bore and compare the numbers with a 18" Mini-14 with iron sights that are .9" above the bore. Further, let's sight both in at 50 yds and see where they are at 100 and 200yds. Note, the bullets both fly the same trajectory, they just have a different starting angle.

AR: Muzzle: -2.6", 50yds: +0.0" 100yds: +1.5" 200yds: +.56" 300yds: -6.95"

Mini: Muzzle: -0.9", 50yds: +0.0" 100yds: +0.2" 200yds: -4.54" 300yds: -15.45"

The wild difference is wholly attributed to the height difference of the sights between the two platforms. The AR's physical design biases most shooters to use a shorter sight in distance because the performance of the round will give them a plus or minus 1"error from POA to POI within 25 to 225 yds.

Now, lets look at the same two platforms but use a 200yd sight in distance. Everything else is exactly the same.

AR: Muzzle: -2.6", 50yds: -0.14" 100yds: +1.22" 200yds: +0.0" 300yds: -7.79"

Mini: Muzzle: -0.9", 50yds: +1.14" 100yds: +2.07" 200yds: +0.0" 300yds: -8.64"

Gives you something to think about, doesn't it? I sight my irons only AR carbine in at 50yds as it's then good enough for 25-225yds. However, I sight in my Mini-14 at 200yds because that gives me a more useful plus or minus 2" hit distance than the shorter 50 yds sight in. Nothing special about the Mini vs the AR. All firearms with sights low on the barrel perform better over a wide range when sighting in at longer ranges. It's a function of the trajectory and the 'loft angle' the bullet leaves the muzzle at.
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Old 06-26-2017, 06:59 PM
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LOL...............I sight in each of my rifles.......................kind of like my kids ..... individually........

"typical" will get you on paper............................
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Old 06-26-2017, 07:12 PM
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Book figures and book points of impact sometimes correspond with real figures and real points of impact, but not always; best to actually shoot targets with your ammo at various distances to be sure.
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Old 06-26-2017, 08:48 PM
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I like a 100yd zero for my red dots, I use a 50yd zero for my irons.
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Old 06-29-2017, 01:01 PM
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Makes sense to me- I zeroed mine at 100, because I only shoot at 100, 50, or very rarely 200yds. I just know to hold a little low at 50, and I can put all of them on a 7"-10" target at 50 yards, if you can hit a 7" circle with a 5.56, theyre gonna be hurting really bad or quickly dead almost no matter where you hit 'em

and for sport, I like setting several targets out, like 30, 50, 100 yards staggered and pop two on each target to make it feel like multiple targets approaching from different angles and speeds, and it keeps you sharp. Again, if you get most on the target, i'm pretty happy with that. more fun with steel too
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