25 meter sight in?


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SilentStalker
June 3, 2012, 02:01 PM
Ok, I have some questions about the 25m sight in method. I know if you ^^^do this then theoretically you are supposed to be good at 25m and 300m, but does that mean you should only be on mark at those distances or will you be on mark at this distances and pretty much anywhere in between? I hope that makes sense.

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rcmodel
June 3, 2012, 02:08 PM
Bullets follow a parabolic curved path during flight.
(Like water from a garden hose nozzle.)
It is called the trajectory.

The bullet crosses the line of sight twice.
Once on the way up, and once on the way back down.

So, no, if you are zeroed at 25 & 300 yards. the bullet will be below the line of sight at less then 25 yards, above it between 25 & 300 yards, and below it again past 300 yards.

How much depends on several things, including sight height above the bore, and the bullets speed and ballistic coefficient, or drag through the air.

The fact of the matter is however that a 25 yard zero will only get you fairly close at 300.
Perhaps 7" or 10" close.

If you want an actual 300 yard zero, you have to shoot at 300.

See this for perhaps a clearer explanation:
http://www.rifleshootermag.com/2010/11/02/shooting_tips_ballistics_0303/

rc

tech30528
June 3, 2012, 02:42 PM
I've recently had another theory suggested for sighting the 223. Try sighting at 50 yards instead which would put you on at about 200. The theory here is that overall rise at roughly 150 yards is significant (not an AR guy but isn't it about 7 inches?) and that sighting so low in the "pipe " would have a majority of shots which would be in intermediate distances coming in low. By sighting further in to the rise it leaves less to calculate. If you are sighted at half the rise all of your shots in effective range would be further than half of your total rise off in vertical stringing which is likely close enough for all but paper punching.

briansmithwins
June 3, 2012, 02:47 PM
A 50 yard zero works better for .223 for most applications.

Google ' santose improved battlesight zero ' for details.

BSW

jmr40
June 3, 2012, 02:51 PM
At one time (Maybe they still do) the military M-16's were set up to be zeroed at 25 yards. With that zero they were supposed to be zeroed again at 300 yards. This was assuming you were using a military spec A-2 rifle, shooting military spec ammo. Change the ammo, sights, or barrel length and you start changing the points of impact. Since the barrel on an M-16/AR15 is about 2" lower than the sights the bullet would obviously be lower at very close range. At 100 and 200 yards the bullet will hit 2-5" higher than your point of aim.

With the shorter barrels and optics so common on the military M-4's now I don't know how they are zeroing their rifles.

I understand the reasoning behind the 25/300 zero, but never liked it for my own use. Almost all of my shots are at 50-200 yards and a 300 yard zero left the bullet hitting way too high at the ranges I was most likely to shoot and zeroed at extreme ranges where I'd likely never shoot. I still prefer a 100 yard zero. With virtually all modern chamberings this means the bullet is never more than 1" either above or below my line of sight between about 30 yards out to almost 200 yards. Only 2" or so low at 200 and around 6-7" low at 300. I find it easier to allow 6-7" of hold over at long range than 5" holding low at close ranges.

elrowe
June 3, 2012, 02:58 PM
You can also intentionally zero below the point of aim at 25m to match the point of impact with a 100m zero. In the case of my .30-06 with Nikon scope, hitting 1.16" below point of aim is the same as zeroed at 100m. This is helpful when you don't have a range that is as long as your desired zero distance (like if you only have 100m range and want a 200 or 250m zero). Nikon has a pretty good calculator at:

http://www.nikonhunting.com/SpotOnRegistration/

For the more mathmatically inclined, both Speer and Barnes have good tables in their reloading manuals. None of these methods will get you to competition quality zeroes, but will put you on to point-of-deer-vitals accuracy to at least 300m with bullets in the 2700 fps and up realm.

Buck Kramer
June 3, 2012, 04:11 PM
AK's are factory sighted at 25 meters, then it will always be within 16" of center all the way out to 1000 (elevating the rear sight of course). While 1000m isn't all that practical for an AK, its a cool idea.

rcmodel
June 3, 2012, 04:19 PM
I propose that you can't see a sight-in error at 25 yards well enough to accurately sight in at 300, or 500, or yes, 1,000 yards.

I will go so far as to say a 25 yard sight-in wouldn't even be on paper at 500 yards most every time you try it.

The 25 yard zero works for the military because close is good enough for the average grunt who isn't a very good shot anyway, and gets very little if any long range training.

But it won't work well at all for a sniper, or big game or varmint hunter, or match shooter.

rc

Shadow 7D
June 3, 2012, 04:22 PM
Don't forget it DEPENDS
um, don't forget ammo variations
http://7.62x54r.net/MosinID/20050122M9130b.jpg

This is a chart from 7.62x54r.net on ballistic variations of a HUGE number of different ammo, the also analyze each ammo type, anywho, you can see the change

so, yeah the basic idea, but it depends on what rifle you are shooting, what works for 223 isn't the same as .308 or .270 etc.

txgunsuscg
June 3, 2012, 07:51 PM
I propose that you can't see a sight-in error at 25 yards well enough to accurately sight in at 300, or 500, or yes, 1,000 yards.

I will go so far as to say a 25 yard sight-in wouldn't even be on paper at 500 yards most every time you try it.

The 25 yard zero works for the military because close is good enough for the average grunt who isn't a very good shot anyway, and gets very little if any long range training.

But it won't work well at all for a sniper, or big game or varmint hunter, or match shooter.

rc
500? No, haven't tried it. But with a 25 meter zero and my AimPoint, I have hit side-silhouette moving targets at 300, so it can't be that far off...

Sniper zero, no. Good enough for defensive use, yes...

jmr40
June 3, 2012, 08:26 PM
The purpose of the military 25 yard zero was just to get things close enough. They even issued special scaled down targets made to scale that would match a 300 yard human sihlouette for a 25 yard battle sight zero. If at all possible they do/did fine tune the sights for longer range. But if sights needed to be adjusted in the field and a 300 yard range was not available this was used.

Once dialed in the rear sight was calibrated and could be adjusted out to 800 yards. Once again this only works with the older A-2 versions with the built in carry handle, 20" heavy barrel and with 62 gr milspec ammo. Years ago when I bought my first AR I had my BIL, a Marine at the time, teach me how they trained him. I never tried anything beyond 300 yards, but he says it will work out to the 800 yard mark as long as everything is adjusted properly and the correct ammo is used. My BIL retired in 2006 after getting back from Iraq the 2nd time and I have no idea how they are now training soldiers using the M-4 with optics. He was artillery and was still being issued the A-2 and Beretta even as late as 2005.

I've since moved on to flat tops with optics and now zero at 100. That works for my needs.

mdauben
June 3, 2012, 10:32 PM
You can also intentionally zero below the point of aim at 25m to match the point of impact with a 100m zero.
I have actually seen sight-in targets like this. They have two "bullseyes" and if you aim at one and hit the other at 25yrd, you should be on target at 125yds(not totally sure about the final range?).

These were specifically for ARs shooting 5.56mm, though. I would imagine other calibers would need different targets.

adelbridge
June 4, 2012, 12:31 AM
I have used the 25 yard/meter sight in in lieu of bore sighting. You are close enough that you should be on paper. Last gun i sighted in using this method was my 20" AR-10 in .308. I shot maybe 5 rounds to get close at 25 yards and I wasn't even on the paper at 100 (shoot way high). Caliber, ring height, barrel length and ammo type are all the wild cards that need to be sorted out on an individual rifle.

s.allen76
June 4, 2012, 12:53 AM
5 years as an active grunt, and I challenge the claim that grunts are not good shots. Anyway, the 25/300 meter zero is designed to put a "grunt" +/-3" from the end of the barrel out to 300M. Aim center mass on a target out to 300 meters with this zero and score a kill shot. Most combat takes place within this range, so this is the common zero used.

DPris
June 4, 2012, 03:41 AM
I've tested the 25-YARD zero with four ARs in various configurations & four bullet weights.
Zeroed at 25, shot at 50, 100, and 200 yards.
100 yard impacts were several inches high, some impacts at 200 yards were over 10 inches high.

Where they would have been at 300 I don't know, didn't have a 300-yard range handy.
But, realistically, how many of us shoot to 300 yards anyway?

I could not have expected to be accurate on a grapefruit at 100 yards with that zero without making some guesswork in sight picture hold-under.

The 25-yard, or 25-meter, zero is NOT reliable once you start to get near 100 yards, and certainly not at 200.

RC is right- if you want to hit at 300 (or 100 or 200), you zero for that distance.
Denis

shuvelrider
June 4, 2012, 05:38 AM
The military is not expecting you to keep your rounds in a dime size group at 300 meters, the idea of "center mass at that distance is to guarantee a kill shot or at least an incapacitating wound. Remember, in reality the center mass of a enemy combatant is roughly a 15 inch circle as indicated on the zero target.

On zeroing you strive to keep the group small at 25m, that is also an indicator of proper weapon hold and applying the fundamentals, the grid target also shows how to adjust your weapon to achieve your "zero" point.

Some of the armchair experts who "propose" the military can't shoot and that close is good enough has not experienced the military. The 25m zero target replicates your sight picture at 300m. If your weapon is properly zeroed then any soldier should be able to pick it up and qual with it, and or engage targets out to 300m. Providing the soldier is doing their part also, (BRM) skills.I've done it and have seen other's do it, by using someone else's weapon.

Very much agree with S.Allen in post #14, 21 years of service for me and still going.

Shadow 7D
June 4, 2012, 06:44 AM
On zeroing you strive to keep the group small at 25m, that is also an indicator of proper weapon hold and applying the fundamentals, the grid target also shows how to adjust your weapon to achieve your "zero" point.

this is riight
BUT I disagree with you a few other points, battle sight zero is the return point (and one you should know how you shoot on) since each person's sight picture etc. is individual to them, picking up somebody else's rifle, doesn't mean that YOU will hit the same spot they hit when they shoot. Fundamentals means you that you group small, not hit the bulls eye cold with any gun you shoot. BRM skills are important, however, outside combat arms, they are SECONDARY in the US Army to primary MOS, I learned more about shooting AFTER I left the army, that said, the BASIC skills learned in basic training are the fundamentals, and have provided me a basis to build off of, but they were more concerned about you hitting and dropping a target (and getting the company off the range before the chow hall staff went home (cause we wouldn't be there before they closed)

shuvelrider
June 4, 2012, 11:09 AM
By all means, I hope I did not imply multiple shooters on the same weapon will all group the same, far from it. I,m saying I zeroed my weapon and qualed with it. I gave that weapon to 4 other soldiers who also qualed with it, without changing my settings. Very much so they will have a different sight picture and shot placement, my point was about the weapon being zeroed properly in the first place
Yes , battle zero (mechanical zero) can be employed with a strange weapon so that a soldier can engage the enemy, the soldier may not have the time to do so.
Your unit like many others (mine also) get caught in the "Train to Time" mentality rather then to standard. I've argued that point many times to use the extra ammo for individual blocks of instruction, plenty of NCO's to coach "slower" shooter's. Also to train in alternate positions and techniques, always met with resistance to that.
Also have seen soldiers rushed through the zero process to go and Qual, looked at their target and told them "no way, your next to center mass,not in it and your grouping is to big" . I'll go back with them and be their coach on the line, nice when they tell you after they qual "thanks for your time to help me zero".

beex215
June 4, 2012, 12:01 PM
yes the 25 meter military zero is still going on. works with m16s and m4s. also they have simulated targets shrunked down to shoot at 25 meters as if you were looking at the target from 300 meters.

even though you are shooting at 25 meters, your sights are set at 300 at all times.

qualified 38/40. kneeling kills me, im too shakey.

DPris
June 4, 2012, 01:18 PM
With a 25-yard zero, you may be able to strike a man-sized silhouette at 300, but if most of that silhouette's behind cover with only a head exposed, you may not. Or at 200 yards.

I prefer a tighter group that I know will have better chances of putting a bullet into a smaller target at distance.
Nowdays my ARs are zeroed 2 inches high at 100, which gives me a realistic shot at rabbits & larger targets out to roughly 200+ yards, the max I'd expect to need.

The degree of "rise" from a 25-yard zero also varies from gun to gun depending on barrel length and sighting options. Same with the load used.
A 25-yard zero just gets me on paper for final zero as mentioned above; only a beginning point, not an end point.
If you want to increase your chances of a more precise strike at 100, 200, or 300, you zero at those distances.

I want more than mere "torso capability" at longer ranges than a 25-yarder gives me. I'm not planning on going into battle with my guns, but they need to do better than that.
Denis

txgunsuscg
June 4, 2012, 02:00 PM
With a 25-yard zero, you may be able to strike a man-sized silhouette at 300, but if most of that silhouette's behind cover with only a head exposed, you may not. Or at 200 yards.

...

The degree of "rise" from a 25-yard zero also varies from gun to gun depending on barrel length and sighting options. Same with the load used.
A 25-yard zero just gets me on paper for final zero as mentioned above; only a beginning point, not an end point.
If you want to increase your chances of a more precise strike at 100, 200, or 300, you zero at those distances.

I want more than mere "torso capability" at longer ranges than a 25-yarder gives me. I'm not planning on going into battle with my guns, but they need to do better than that.
Denis

Well, the guy next to me won our bet by putting 3 rounds into 3 moving torso targets (19 inches wide), and his final round into the head of the moving target (8 inches wide and yes, he called it), versus my 4 rounds into 4 torso targets. Targets were shot consecutively.

As for specs, 62 gr FMJ, non-magnified AimPoint CompM2s (4 MOA dot, so it covered roughly 12 of the 19 inches I was shooting at), and 10.5 inch barrels.

Yes, you could zero for multiple ranges, but that assumes you have an adjustable optic. If you don't, you can zero at 25, then shoot at 100, 200, and 300 and just know your hold so that you can quickly adjust to targets that pop up at multiple ranges.

And people that do go into battle with their guns trust the 25 meter zero....

shuvelrider
June 4, 2012, 02:03 PM
There's no "may" about it, I can hit the silhouette at 300m, per instruction on engaging man size targets at that range. Now, changing the parameters of discussion to tiny targets means I now employ supressive fire to supress the threat from that location. I could "mass" fire on that point, or I could bring to bear the skills of a sniper team with better equipment. but that's a whole nother topic of discussion.
Or, I could continue to engage with my rifle by "drawing down" a finer sight picture/point of aim on the target. We are talking about a "standard course of instruction for the majority", a basic standard to teach quickly to large number's of troops. Some who have never fired a weapon to those with lots of experience already, some who bring bad shooting habits with them that have to be "unlearned".
Civilian shooting and whats available on the AR market is a different world all together.

Striker
June 4, 2012, 02:33 PM
And people that do go into battle with their guns trust the 25 meter zero....

Concur.....been there done that, and may/would do so again.

YMMV

SilentStalker
June 4, 2012, 02:48 PM
Ok, so basically there is no magic way to say get a perfect headshot of a silhouette at any distance between 10-400 yards without hold over or under is what you guys are saying. So, basically if I am engaging something from 25 yards or closer I am going to have to aim lower, how much is kind of guesswork, and then if I want to engage something say 100 yards or more I am going to have to hold over or aim up, correct? The problem here is, how the heck do you determine how much to holder over or under? How on earth would a sniper ever hit his target the first time. I mean I guess if you shoot a lot and you shoot a lot at different distances then you know exactly what adjustments to get your rifle on center at 100, 200, 300, and so on yards. I imagine that is why they keep their little book handy, huh? I am guessing that little book is where they write down what adjustments they did to get their rifle on target at different given distances. That would make sense. So, what you are telling me is that I need to keep a little book like this for each rifle, more or less, so that when I take it out I know how, where, and how much to compensate. Wow, there is a whole lot that goes into this stuff.

And then, if you change barrels I imagine that you have to go through all of this junk all over again, huh? Wow, why on earth would you ever want more than a handful of guns? Thinking of this stuff I don't think I would ever want more than 5.

velocette
June 4, 2012, 03:16 PM
Here are ballistic calculations for a 62 gr bullet @ 3000 fps
sight 1 1/2" above bore, zero @ 25 yds.

Range Velocity Impact Drop ToF Energy Drift
0 3000 -1.5 0 0 1239 0
50 2855 1.25 0.6 0.05 1122 0.65
100 2720 2.932.28 0.11 1019 1.3
150 2591 3.43 5.13 0.16 924 2.41
200 2465 2.64 9.28 0.22 837 4
250 2343 0.4 14.87 0.29 756 6.11
300 2225 -3.43 22.05 0.35 682 8.79
350 2110 -9.01 30.99 0.42 613 12.06
400 1998 -16.56 41.89 0.49 550 15.98

As you can see, the bullet is 3 1/2" above POA at 150 yds and 3 1/2" below POA at 300 yds. (impact column) Easily good enough for hunting man or beast.
Thats what the 25 yd zero is all about. The drift calculation is for a Full value wind (10 kt) at 90 degrees to the line of flight. ToF is time of flight in seconds.

Roger

txgunsuscg
June 4, 2012, 03:41 PM
The book you are referring to is the DOPE book (Data On Previous Engagements), and it is exactly what it sounds like - a running log that documents their shooting at various ranges, under different environmental conditions, even the lot number of the ammo they used. From the logged shots, they pull information that helps them judge their dope for the cold bore shot. It's part science, and part art.

For my rifle in 5.56, I hold over for under 25 (between 1-3 inches), and under for between 26 and 299, usually between 3-6 inches. Because of the bullet's trajectory, which is an arc (in order to defeat that d*** gravity), the bullet "rises" from 0-25 where it crosses the zero, and continues to rise through 100 and 200 (the rising branch) until reaching its highest point (max ordinate, usually between 2/3 to 3/4 of the way to the target), and then falling (falling branch) until it crosses zero again at 300.

henschman
June 6, 2012, 02:00 PM
I know it was assumed in everybody's post which rifle we're talking about here, but since the OP didn't mention it, I want to clarify that the 25/300m zero is only for an AR-15 with a fixed carry handle and standard issue 55 grain M193 or 62 grain M855 ammo. Any other rifle will also have a "second zero" if you zero it at a short distance like 25m, but where that second zero is will depend on the height of the sights above the bore, the velocity of the bullet, and the ballistic coefficient of the bullet.

For instance, on an AR with a detachable carry handle, the sights are actually a little higher above the bore than on a fixed carry handle rifle... so with a 25m zero, the second zero is actually a 320m zero or so. That is why the detachable carry handle rear sight has a little "z" mark 1 MOA higher than the 300m setting on the elevation drum. If you zero the rifle at 25m with the rear sight set on the "z" mark, you have to adjust it back down one click to get to your 300m setting.

All this is done with the small aperture. The big aperture is 2 MOA lower than the small one, so if you are zeroed at 300m with the small aperture, flipping to the big one gives you a 50/200m zero.

Texan Scott
June 6, 2012, 04:24 PM
Most of us who were issued M-16s and taught the 25-300 yd zero thing prob. realize that the military in general is not overly concerned with shot groupings by the average serviceman. As long as most of us shoot well enough to hit the enemy somewhere most of the time, and they throw enough of us at the problem, we stand a good chance of winning.

This has never seemed satisfactory to me, either as a man who wanted to survive a combat engagement at rifle range (which never happened to me- airstrikes are called in best when the target doesn't know you're watching :neener: ) or as a man who wanted to put meat in the family freezer with minimal fuss.

I would still sight in a new rifle at 25 yards first, but only to be sure i'll be on paper at 100yds. if i were shooting a 300 yard rifle, i'd sight in at 25 to be on at 100, then sight in at 100 to be on at 300 (because nothing i've ever hunted with shoots NEARLY as flat as 5.56 ball).

Somebody on THR (apologies, don't remember who)has this sig line: "In theory, theory and practice are the same. In practice, they aren't."

^^ this is an astute observation. ^^

Old Dog Man
June 7, 2012, 01:31 AM
I have sighted in many rifles in my years, I always start at 25yrds. to get on target (saves customer money). Starting at 2-3" low, have had some shoot low at 100yrds. and some shoot very high, you should try your rifle and ammo and find out for sure what your set-up will do. Al

DPris
June 7, 2012, 02:35 AM
My uniformed days are behind me, I am not interested in either military or LE engagements anymore.
For MY purposes, I want to be able to hit an approximately grapefruit-sized target out to a max of 200 yards, using basically the same sight picture & hold. That'll handle rabbits at 100 and coyotes at 200 without much guesswork.
I want to reduce the guesswork.

If my guns are zeroed at 25, it reduces my chances of being able to use pretty much a center-point aim, or a point-blank aim, at 100-200 yards.

If I zero my guns 2 inches high at 100 yards, I can use pretty much the same center of mass (and that's a SMALL center of mass, not a human torso-sized center of mass) hold from 100-200 yards, with a much higher hit probability.

My goal in zeroing is to reduce making guessworked physical adjustments by having to move the sights as distances increase any more than I have to.

In the four ARs I tested from 25-200 yards, the degree of bullet "rise" at longer distances varied between bullet weights from gun to gun, barrel lengths from gun to gun (velocity variations), and sight types (standard carry handle, and three different optics).

In my own testing, in my own guns, I found the 25-yard zero's chances of striking a grapefruit-sized target inferior to a longer zero's chances, using the same sight picture.
If I zero at 25, I HAVE to aim lower for a 200-yard target. If I zero for that 2 inches high at 100 yards, I don't.

Those are my direct experiences in real life with my guns & different loads, and they are the reason that I'll continue to zero my ARs that way.
I zero long to strike long.
Denis

henschman
June 7, 2012, 03:25 PM
With an AR, if you want to hit more like grapefruit-sized targets at closer ranges, from your 300m zero, just flip to the big aperture. That is a 50/200m zero, and will only be off a couple inches either way from point blank out to 230m or so.

DPris
June 7, 2012, 03:51 PM
If I were using an aperture... :)
Denis

lloveless
June 7, 2012, 11:50 PM
I zeroed my DPMS LR308 at 25 yds. It then shot 6 inches high at 100 yds. Tomorrow I'll change that to a 3 inch high at 100. This is in a 16 inch barrel and 150 gr bullets.
ll

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