Zeroing a rifle question..

I don't get the practicality of a 25 yard zero...
It imposes a rather steep muzzle angle, making the round far more inaccurate at closer ranges than it need be. According to the chart above, nearly 4" high at 150- where's the advantage in that?


Dont plan on 800m with a mosin unless your just playing around.
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I can bang 8" steel at 600 yards with my Mosin sporter. You don't know what you're talking about. The ballistics of the 7.62 x 54R are quite capable of long range- right up there with the 30.06.

Go bone up on your ballistics tables...
 
When a bullet is fired it typically meets your line of sight twice, once on the way up and again on the way down to meet your zero, much like throwing a rock - more distance untill target = higher trajectory needed untill it comes down to hit target. The faster your bullet and higher your ballistic coificent is the less noticeable this is. What they (Army) probably did is zeroed at 300 then moved in untill it was on zero again. If you tell me what ammo your using and what range you want your rife zeroed I can give you the first point of intersecion...
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The Gunny got it right, as did some others. The bullet crosses the line of sight twice. Zeroing at the closer range puts the bullet back on target at the longer range, with the bullet being high at midrange. For the hunter, zero as far out as possible without being too high in between.

You can zero all rifles for the same closer range, but, as mentioned, the velocity and load determine where it crosses the line of sight the second time (zeroes).

Battle sight zero is about 250 or maybe it's 300 meters. The idea is to put the sights on the enemy's mid section and hit him somewhere.

For many of us in the urban environment, a 100 yds. zero is fine. Remember our rules of engagement are different. Better have a good, court defensible reason for shooting someone at distance.
 
This is where my question comes in for the M4 as well as a sniper rifle that I am building.
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You are building a sniper rifle while you are still struggling with basic ballistics? My, you are an ambitious fellow. I'm sure you'll get it all down soon.

The base reason is gravity. The bullet starts dropping as soon as it leaves the muzzle. And its moving "sideways" pretty fast,as it falls.

To compensate for this (as much as we can) gun barrels are "pointed up", compared to the line of sight, which is straight at the target. Although they look parallel to the eye, the line of the bore and the line of sight are not. So the bullet is fired "up", and crosses the line of sight going up a short distance from the muzzle.

Then as it flies downrange, falling, it crosses the line of sight again, on its way down. The distance from the muzzle where this happens is where your sights and bore are "zeroed". Adjusting the sights allow us to decide at what range that second crossing happens, 100, 200, 300yds, etc.

Velocity and bullet construction determine the arc of the trajectory. For the M16A1 using the GI ball ammo of the 1970s (which I have personal experince with), hitting a certain spot on the 25 meter target meant that you would hit the desired spot at 250 meters.

This principle will work for all rounds, and to zero at any chosen distance, all that needs to be done is calculate the right spot on the 25 meter target. It will be different for different guns and loads.
 
"Sniper rifle" = a weapon used to kill 2 legged prey.

The term is used pretty loosely around here...just call it a "precision" or "tactical" rifle...
 
It imposes a rather steep muzzle angle, making the round far more inaccurate at closer ranges than it need be. According to the chart above, nearly 4" high at 150- where's the advantage in that?
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I am thinking that if I am aiming for COM chest and I hit 4" high that ain't all bad.

"Sniper rifle" = a weapon used to kill 2 legged prey.
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He might not be talking about kangaroo. He might be talking about snipe.
 
I don't get the practicality of a 25 yard zero...
It imposes a rather steep muzzle angle, making the round far more inaccurate at closer ranges than it need be. According to the chart above, nearly 4" high at 150- where's the advantage in that?
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The practicality of a 25yd zero is that it is done at close range. If you don't have access to a long (250yd, or whatever) range, and still want to be zeroed for that distance you can do it. You just need the right target for the gun/load you are shooting. For 25yd zeroing, you aim at a certain point on the target, and your rounds hit another point on the target, one calculated to put your rounds on the point of aim at a longer range. You do not sight to hit point of aim on the 25yd target.

As to the "nearly 4" high at 150..." there's no free lunch. If you want your bullet to be on target at 250 (for example) then it WILL BE HIGH at shorter ranges. How much high it will be depends on the specific bullet and speed.

If you want to be on target for a shorter range, sight in for that shorter range.

Remember, your sights will only be "on" for ONE range, at a time. In other words, you can only sight in for your point of aim and point of impact to be the same at one range at any given time. Hitting at any other distance is a matter of knowing how much drop below, or rise above the line of sight to compensate for. Thats how shooting works.
 
I don't get the practicality of a 25 yard zero...
It imposes a rather steep muzzle angle, making the round far more inaccurate at closer ranges than it need be. According to the chart above, nearly 4" high at 150- where's the advantage in that?
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The army spent a lot of time and money working out a system that is butt simple to use. The concept is called battle sight zero. An m4 or m16 with G.I. ball zeroed at 25 meters will put solid, center mass hits on a man sized target out to 300 yards without making an elevation sight correction.
 
The army spent a lot of time and money working out a system that is butt simple to use. The concept is called battle sight zero.
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Otherwise known as "maximum point blank range". If you reload, you know its been around awhile. Its part of the ballistic calculations.

These days, with computers, you simply insert the diameter of the "vital" area and plug in the rounds ballistics, and it pumps out the maximum range the round will stay within the circle when the sights are held at the center.

Regardless, you still need to verify and fine tune your sights at the BSZ/MPBR if your serious about hitting at those ranges. If your 25 yard zero isnt perfect, and is just "a little" off, theres a good chance to almost a certainty, that your hits at the other end will be considerably off.
 
I apologize, my comment was kind of vague as to the point I was questioning...
We shoot long range (and I handload) and the only open sight rifles we own are milsurps that don't get a lot of trigger time...but I'm fully aware of MPBR and bullet drop :)

What I was getting at is that it seems to me (just one guy's opinion) that the 25M zero- resulting in the bullet being about 8" high at 200M- looks to be beyond what I would consider to be the "kill zone" for the M855.

Now, I don't know what the military defines the "kill zone" as on a two-legged quarry.

I did a little digging and this article makes the same point I didn't do very well in my first post...in a nutshell, making the argument that the zero should be changed to 50/200 instead of 25/300 keeping the bullet rise lower- and more accurate.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA512331

Consider the following from page 50:

M855 ammunition is only capable of two to three inch accuracy at 100 meters, meaning that at 200 meters the group will be four to six inches. Now add in the human error, which generally, equals about a two to three minute of angle hold error under ideal conditions and there is the potential for shooting about a foot and half high at 200 meters. Most soldiers and leaders are unaware of this problem. When combined with the natural tendency to shoot high during combat, soldiers will typically miss their target.
Figure

Zeroing the rifle or carbine at a distance of 50 meters will keep the maximum ordinate of the M855 round within one inch of the point of aim from 25 meters to 200 meters, where is crosses the line of sight again. This zero combined with the accuracy potential of the ammunition and the shooter will keep the strike of rounds within the chest area of a target out to a distance of 250 meters. This zero can provide lethal hits out to a distance of 320 meters, with rounds impacting in the vascular region of the lower abdomen and groin.

It makes sense to me...
 
MTT-L As a retired Reserve Officer and former Commander I take exception to catagorizing units which use the Alt. tables to qualify as poor. Those decisions are more often made based on Budget and range availability than on bad leadership.

When sighting in a rifle I generally consult a ballasitc table which was published in the 1973 Guns Digest Annual.

This table gives the distance where the bullet first cross line of sight. I set my target at that distance. For example the chart shows that a 308 win 150 grain crosses LOS at 25 yards. Mid range tracjectory is 3.5" high.It is dead on at 250 and 4.5"low at 300 yds.

This puts my shot in the vitals of a white Tail without hold over/under to 300 yards.

Before you jump all over me, this is a guide used to get me on paper without a lot of walking and wasted ammo. Once I establish the 25yd zero I verify at 50, 100 150 250 and 300yds.
 
I'm building a cheap sniper rifle for no more then $300. If I zero this rifle at a indoor shooting range to my "scope" at 25 YARDS, how far is it zeroed to?

THANKS
I'm building the sniper rifle out of a Mosin Nagant 9130.
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The answer is, "It depends"

A standard Mosin Nagant 01/30 PU Sniper rifle has a sight height of about 2.25". Using standard Russian light ball (148gr@ 2812FPS), a 25 yard zero should give a far zero at 320 yards

If you have a lower mounted scope, the traditional default of 1.5" over bore centerline, the a 25 yard zero will give a far zero of 230 yards.

If you are using the iron sights, with a .9" sight height, the far zero would be about 145 yards.

Using Yugo Heavy ball, (182gr @ 2605 fps) the PU scoped rifle gives a far zero of about 305 yards.

The 1.5" sight height gives a far zero of 215 yards. The standard iron sights would give you a far zero of ~135 yards.

All these numbers are from http://www.jbmballistics.com at sea level, 70ºF, and using the bullet weight, average velocity and Ballistic coefficient shown on 7.62X54r.net. Of course you need to reality check these numbers at the real range.

So basically you need to zero the rifle at around 100M for it to be effective 800M+?
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Really, no. You basically have 2 options for long range shooting. Hold over, and adjusting the sights.

Using and example of me, and my rifle, a 6.5-06 built as a LR Heavy Varmint rifle, I do both. I zero the rifle at 200 yards, and I know that it is 1.5" high at 100 yards, and about 7" low at 300.

This covers 90% of normal varmint hunting. I also have a Mil-dot scope, and I use the mil-dots as reference points. The first dot down equates to 350 yards, and the second dot is 475 yards. For Varmint hunting, I leave the scope alone, and adjust my aim (hold over) based on the estimated range to the target.

For long range target shooting, I know the come-ups in MOA for each range. So if I am shooting at 600 yards, I know the drop is 10.7 MOA, so I spin in 43 clicks of elevation on the knob and I am balls on.

Keep in mind your inexpensive scope on your $300 total rifle may not have enough elevation adjustment to get on target at long range. You may need to get a tapered base, or, since it is a Mosin, get a PU scope and mount, then you won't have to worry about it. It has range settings on the elevation knob out to 1300 meters, calibrated for the Soviet light ball. All you have to do is turn it to the target range and send it.
 
Amusing responses to the age old question. The fact of the matter is that most guns shoot better than the shooter holding it and unless you have the gun bolted down to a solid table your results will vary...that's the beauty of 30 round...now even 60 -100...magazines. Out of multiple rounds fired from the magazine one could expect to get at least a few rounds on target....:D
 
I'm gonna make a few recommendations here:

First off, dump the name sniper or even tactical as someone recommended. You are wanting a long range target gun.

Next, dump the idea of "building" a long range mil-surp rifle for $300. Too many production centerfire rifles made today that are a much better starting platform for the same money, new and used.

3rd, get the idea of centerfire rifles out of your head for now. Get/build a .22lr. Savage has bull barreled .22's for around $200 last time I checked. It will teach you ballistics, shooting a .22lr rimfire out to 200 yards requires the same principles as shooting most centerfires at 600 yards (comparable wind drift and trajectory) and it's much easier to find 200 yard shooting opportunities. Ammo is cheaper, guns are generally cheaper, optics are cheaper, upgrade parts are cheaper, etc, etc. Until you've mastered shooting a rimfire there is little to no reason to move on to centerfires at any range let alone long range. Plus nicely set up long range .22's are just plain cool. Especially if you now how to shoot it.

LK
 
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I've shot many and many a sub-MOA group since I first began messing with centerfire. I have found that dead-on at 25 yards is generally a tad high at 100 and that it's not unusual to be a couple of inches to the side. IOW, IMO, zeroed at 25 yards is nowhere near good enough for reliable hits at 300. It's merely an easy way to ensure hitting the paper at 100 yards.

FWIW, I sight in for around two inches high at 100, which generally is about dead-on at 200 and around six inches low at 300. If I know the distance out beyond 300, proper holdover has been no big deal. 500 yards has been the limit of my playing.
 
As stated earlier, you need to verify your long range zero's.

Close range zero's might get you on paper, but the further you go back, the greater the error.

You see this all the time at 1000 yard F Class matches. Guys who have a 100 yard zero and then using ballistic tables, make an estimate of a 1000 yard zero.

Sometimes they spend all of their 20 minute record period time shooting, getting real frustrated, have a cluster of scopers trying to help and never hit the target!.

I will shoot in mid range matches, get a good 600 yard zero, but it is a nail biter first shot with estimated come ups at 1000 yards.

As a general rule, if you have a good 200 yard zero, the come ups to 300 yards, you will be close to center. For a 308 it is like 2 to 3 clicks. However going from 300 to 600, standard come ups will get you somewhere in the black, which is about 36 or 48".

When you get to 1000 yards, better do the rain dance, maybe the range gods will let your bullet be in the black, maybe it will be in the berm.

Sometimes, every once in a while, we think it never gets down there, it just disappears :confused:
 
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You see this all the time at 1000 yard F Class matches. Guys who have a 100 yard zero and then using ballistic tables, make an estimate of a 1000 yard zero.
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The better the data you put in to the ballistic program the better the result will be. If you have a true measured muzzle velocity, and put in all the little stuff that most people think doesn't matter, altitude of the range, measured height of the sights over the bore, even air temp, you are much more likely to be on paper using calculated drop from a close zero.

For what it's worth, the trajectory output of JBM for the above mentioned rifle matches my real world shooting at ranges out to 950 yards.

Garbage in, garbage out.
 
Its kinda funny, the Mosin nagant was sighted to fire ~6" high at 100m. The soldiers were to aim at the belt buckle, hitting the enemy center mass.

Poor man's ballistics, yeah :D


I personally do not like 6o'clock hold on my rifles, gonna file down the rear leaf sight on my mosin.
 
Drop a bullet and fire a bullet (same type) at exact moment will hit the ground at the same time?????? If you drop a frizbee and throw a frizbee will they hit the ground at the same time? If the statement is true, then bullet BC has nothing to do with trajectory.

A lot of things effect bullet trajectory. Speed, shape, and the weight are the obvious. RPS, Humidity, and altitude also have and effect.
 
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