# Help Me Sight In My 308



## biged156

how high or low do i need to sight my 308 in at 25 yards... i am using winchester supreme silvertips with 168 grain.  or can you recommend any good website on ballistics thanks


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## Jeff Phillips

Get it dead on at 25 yards, then shoot it at 100. 

Depending on your bullet selection, 2" high at 100 will put you dead on at 200.

http://www.federalpremium.com/products/details/rifle.aspx?id=33


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## Dead Eye Eddy

I've never shot a .308, but I like my .30-06 and .270 1" low at 25.  That puts me about 2-3 inches high at 100, and I've killed deer with a dead-on hold out to 250.


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## germag

Dead Eye Eddy said:


> I've never shot a .308, but I like my .30-06 and .270 1" low at 25.  That puts me about 2-3 inches high at 100, and I've killed deer with a dead-on hold out to 250.



You must be using some high scope mounts and rings......


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## ScottD

*25 yard sight in*

The Point of impact at 25 yards is not a function of the round or caliber - it is a function of the distance from the scope center to the bore.


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## Bone Buster

*308*

I just sighted in my new Hawkeye 308. I had mine dead on @25yds and was 8' high @100yds so I moved it down to 2 1/2' high @ 100yds. I would say you would probaly be about 1 to 2 in. low @25yards. But I would try it the way I did it 1st just to make sure!


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## VHinch

If you're zeroing to hunt with, battle zero it at 25 and with a .308 you'll have a point blank of 275 or so.  If it's a target rifle, you need to actually zero.


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## germag

ScottD said:


> The Point of impact at 25 yards is not a function of the round or caliber - it is a function of the distance from the scope center to the bore.




Yeah, that's the point I was trying to make. For him to be 1" low at 25y and 2"+ high at 100y the scope would have to be probably 3" above the bore.


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## ScottD

*Germag is correct*

Here is the math

25yards = 900"
100 yards = 3600"

so if x is the measure between the scope center and the bore then

(3600/900)*X is about how high you will be at 100 yards.

so if your scope is 2" above the bore (3600/900)*2 = 8

you will be about 8" high at 100 yards.


the reason I say about is that most centerfire weapons will have about the same trajectory out to 100 yards but there will be a slight difference.....slight


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## bighonkinjeep

You owe it to the game you hunt to make a clean ethical kill. Do yourself  a huge favor and sight your rifle at  reasonable hunting ranges.It's the truest way to tell what your rifle is really doing. Watching a game animal runoff wounded or die from a poorly placed shot is not on my list of favorite things to do. A high powered rifle should be sighted in at at least 100yds.
BHJ


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## Dead Eye Eddy

germag said:


> You must be using some high scope mounts and rings......



All of mine and my dad's rifles have 50 mm scopes mounted in Leupold high-elevation rings.  I don't have access to a 100-yard range, but I can get about 80 yards at Wilson Shoals WMA.  With a 1" low at 25 yards zero, I'm about 1.5-2" high at 80 yards.  I shot a buck at 100 yards last season, and hit about 2.5" above my aiming point, but it put him down, so I didn't care.  I was aiming at the shoulder as he walked across my right of way.  I hit him high-shoulder and he went right down.  I've aimed dead on and killed other deer at 145 yards and 250 yards, and I just missed (shot in front of his shoulder) a running coyote at 315 yards last season with a slightly-high hold.  My zeroing technique works for me.


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## Dead Eye Eddy

bighonkinjeep said:


> You owe it to the game you hunt to make a clean ethical kill. Do yourself  a huge favor and sight your rifle at  reasonable hunting ranges.It's the truest way to tell what your rifle is really doing. Watching a game animal runoff wounded or die from a poorly placed shot is not on my list of favorite things to do. A high powered rifle should be sighted in at at least 100yds.
> BHJ



Not everyone hunts where they can shoot 100+ yards.  If you mainly hunt woods, then a 25-yard zero may be best for you.  It would be easy to miss a deer low at say 20 yards with a rifle that was sighted dead on at 100 yards.


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## germag

Dead Eye Eddy said:


> Not everyone hunts where they can shoot 100+ yards.  If you mainly hunt woods, then a 25-yard zero may be best for you.  It would be easy to miss a deer low at say 20 yards with a rifle that was sighted dead on or 1" high at 100 yards.



But you see, not everybody has their scope mounted as high as you apparently do. How high or low or dead-on you zero for at 25 yards or 100 yards will depend largely on how high the axis of the scope is above the axis of the bore. If your scope is mounted the normal 1 1/2" above the bore, then a 25 yards dead-on zero @ 25y will put you about 1.5" to 2" high at 100y. You can't really just across the board advise everybody to sight in for 1" low at 25 yards and claim that they will be 2 or 3 inches high at 100y....it just doesn't work that way. 

Also, there's simply no way that sighting 1" high at 100y will cause anyone to miss a deer at 20 yards by shooting under it. The absolute most you can hit below POA @ 20y with a 1" high at 100y zero is whatever the distance is between the axis of the scope and the axis of the bore....usually 1.5 inches. 

A 25 yard zero is not a bad thing, though....assuming the zero is also verified for at least 75 to 100 yards. A 25 yard zero for, say a .30 caliber bullet with a MV of 2650 fps(assuming a 1.5" scope height), would put you about 2.7" high @ 100y. But, the 25 yard zero is only the near zero....the far zero is about 220 yards. So the trajectory of that bullet would be:

25 yards    +0.1"
50 yards    +1.3"
75 yards    +2.2"
100 yards  +2.7"
125 yards   +2.9"
150 yards   +2.7"
175 yards    +2.1"
200 yards     +1.1"
225 yards     -0.3"
250 yards     -2.2"
275 yards     -4.6"
300 yards     -7.4"
325 yards     -10.8"
350 yards     -14.7"
375 yards     -19.1"
400 yards     -24.1"

So you see that in this case the useful PBR for this particular round for the purpose of deer hunting is about 275-300 yards.

With a 3" distance from the bore axis to the scope axis, the whole thing changes. So....your technique works for you because you have your scope mounted very high...most people don't.


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## Dead Eye Eddy

Makes sense Germag.  I never realized that the height of the mounts made that much difference in the impact of the bullet at various distances.

I've always heard people talking about zeroing 1" high at 100 yards.  I've never understood that (until now), because for me, I'd have to zero about 2-3" low at 25 to be 1" high at 100.  I like to take neck shots inside of 50 yards, and that could cause me to miss (or lose) a deer close to me.


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## germag

Dead Eye Eddy said:


> Makes sense Germag.  I never realized that the height of the mounts made that much difference in the impact of the bullet at various distances.
> 
> I've always heard people talking about zeroing 1" high at 100 yards.  I've never understood that (until now), because for me, I'd have to zero about 2-3" low at 25 to be 1" high at 100.  I like to take neck shots inside of 50 yards, and that could cause me to miss (or lose) a deer close to me.



Well, think about it like this: Your line of sight through the scope is perfectly straight. If your scope is mounted 1.5" above the bore, then you have to angle the barrel upward some to make the line of sight and the bullet path intersect....if you didn't do that, if you had the bore of the rifle and the scope axis exactly parallel, then you would never be "dead-on" at any distance. You would always shoot low....1.5" low at the muzzle and increasingly lower as gravity pulls the bullet to the ground. So, if you want to be zeroed "dead on" for instance, at 25 yards, then you need an upward angle on the barrel sufficient to make up that 1.5" in the first 25 yards so that your line of sight through the scope and the bullet path interstect at 25 yards....that means that the bullet is going to cross the line of sight and continue upwards at a diminishing angle (due to the effect of gravity) until it starts to descend and then it will cross your line of sight again on it's downward travel. The result is that the bullet travels in a big arc. The first time the bullet crosses the line of sight is the "near zero" point and the second time is the "far zero" point. That's the two points that you will be "dead-on". 

If you have your scope mounted 3" above your barrel, then obviously you need a steeper upward angle on the barrel to achieve a near zero at 25 yards. What that means is that your impact point at 100 yards will be even higher than it was when the scope was 1.5" above the barrel.

You're zeroing for 1" low at 25 yards and it's putting you 2-3" high at 100 yards. That means there is quite a bit more distance between your scope and your barrel than the normal 1.5".


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## wildcatt

*shoot*

I would rather use a 94 winny at upto 100yrds than go thru all that.


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## germag

It ain't rocket science. Understand the trajectory of your bullet, know the ranges you will be shooting at, zero accordingly. There are plenty of free online resources that will plot your trajectory for you...all you have to do is plug in bullet weight, caliber, velocity, scope height, and distance you want to zero for and it will give you everything you need to know....of course it all needs to be verified at the range, but you need to do that anyway.


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## ScottD

*germag*



> It ain't rocket science



Actually it is pretty close to rocket science.


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## germag

ScottD said:


> Actually it is pretty close to rocket science.



Well....now that you mention it.....


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## Dead Eye Eddy

Thanks Germag.  Who says you can't teach an old dog new tricks?   Out of curiosity, I'm gonna measure my scope height and the exact height of my groups the next time I zero.


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## poolman67

Germag great job explaining. If you shoot long range don't use see though mount, the closer your scope is the barrel the better.


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## SC Hunter

I don't worry about zeroing in my scope i just pull the pin on the grenade and let it fly!


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## Georgiaoutlaw

Rocket science is about as close as u can truly explain true  ballistics every gun and every scope and mount is completely different u have to zero for what u expect ur targets to be especially if ur shooting at one of God’s animals u owe it to him and them


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## spurrs and racks

*25 yard*

gets you on paper....nothing more.

I have seen many, many people on paper @ 25 yards and be way off @ 100 yards.

Take your time, start up close, move out slowly and shoot 3 shot groups from 100 yards and any distance farther.

There are pie plate shooters and there are thumb nail shooters. It depends on where you want to be.

If you are raw (only a bore sight) buy 2 boxes of shells before you get started.

Use a rest. Shooting bag, vise, rolled up blanket....something.

s&r


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## biggdogg

Some folks must be awful bored to answer a question that was posted 9 years ago...


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## ryanh487

If you're shooting federal ammo, they have a handy app that you can pull up the ballistics charts/trajectory for any federal factory load.

Every rifle is a little different though, so it's more of a guidline than a fact sheet.  It's a good starting point.


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## spurrs and racks

*ok*

I got bit

s&r


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## killerv

I'd advise getting more than a 1/2 acre to hunt so you can shoot further than 25 yards.

If 25 yards is your only option to zero a gun in, put the gun up and grab a bow.

I hope for the deers sake the bullet hits its mark.


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## GunnSmokeer

Yeah,  9 year old thread ....   


but here's a handy resource to know about rifle ballistics, trajectory, and finding your zero points (close and far, or "first zero" and "second zero") based on scope height above bore:

gundata.org

http://gundata.org/ballistic-calculator/

You can adjust the scope height to any value you want.

You can pick your own zero point, and the computer will run the rest of the numbers for you.

You can set it to show you how the bullet is performing at every 25-yard increment, or 50, or 100.  Out to over 1000 yards. 
I think one time I ran the ballistics for a .300 magnum out to 1500 yards, on a whim.

One thing you CAN'T do is choose any particular load known to mankind.  You have to pick from one of the specific factory loads listed. But for most popular rounds, they have many, even dozens, of different loads from several popular ammo makers, featuring various bullet weights.  

If you can't find your exact load in the database, you can pick the closest load they offer and then adjust the numbers for muzzle velocity or ballistic coefficient (if you know it). You can plug-in any numbers you want for those settings, if you aren't going to go with what comes up for the default on a particular factory load.

P.S.   I like to sight in my rifles at 100 yards, rather than 25.  A small error at 25 may go unnoticed, but when you magnify it by 4X the distance, then it becomes visible in your group on paper.   A couple inches high at 100 is what I use for open fields or power line clearings where I might get a 400 yard shot (athough I  doubt I'd pull the trigger on a game animal that far out unless I had an excellent steady rest, and no wind, with a perfect broadside shot).

For most purposes, being "dead on" zeroed at 100 is fine, and you just have to remember to 
--aim a couple inches high at 200
-- aim a foot (10" to 15" depending on your bullet) high at 300
-- aim 2 feet  (could be 20" to 36" depending on your load data) high at 400.


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## bfriendly

biggdogg said:


> Some folks must be awful bored to answer a question that was posted 9 years ago...



I just got my first .308 so i am glad this came up......looks like I gonna try and set up 1.8” high at 100 with the ammo I got....

How long to let barrel cool?   Does it matter as long as I’m not shooting round after round?


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## Blackston

I shoot a “ cheap “  mossberg and it shoots crazy after 3 rounds.  I only shoot 3 and then let it completely!! Cool if not I’m chasing the bullets all over the target ( yes I’m using a Caldwell sled no weights )


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## lonewolf247

bfriendly said:


> I just got my first .308 so i am glad this came up......looks like I gonna try and set up 1.8” high at 100 with the ammo I got....
> 
> How long to let barrel cool?   Does it matter as long as I’m not shooting round after round?




Yea, this is an old post, but the same ballistic and trajectory principles still apply! This thread pretty well covers the ballistic tables, and with online ballistic calculators, one has access to a lot of good information.

As far as 25 yard zero's, and trying to depend on calculated impacts at 100, 200, or 300 yards only, I'd say no. I start with a new scope mounted on a rifle, at 25 yards to mainly get in the ballpark, and on paper, but move out to 100 yards, for my final zero.  At 100 yards, I usually set my zero 1-2" high, depending on the caliber, for longer range shooting. If 200 yards is available, I sometimes like to verify impact, if possible.

As for cooling the barrel, I try to never fire more than 2-3 shots without stopping to allow for cooling. Usually, when I sight in a new rifle, I will bring other rifles, to shoot in between sighting in the one, I'm mostly concerned  with, even if it's just .22lr's.

Lastly, when I'm sighting in a new hunting rifle from scratch, the final zero, is not something I really can call 100% complete in one day.  Even if I think it's done, I want to go back on a different day, and fire one shot from a cold barrel.  I may even go a couple times and do this before the hunting season.  That cold barrel zero, is the one I want to know, when I actually go in the woods to hunt. 

This may be a little of overkill, and I don't do this with rifles I just plink with.  However, if your trying to take shots at 200 yards, or more, having an accurate zero really matters!


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## bfriendly

Great post lone wolf!  I just set my scope last night, with hopes of perhaps never removing it. I will try to bore sight by removing the bolt and looking through the barrel etc... plan on going to Johns Mtn in the am and finally shoot it! 

Question......this scope has been in the woods before, kind of dirty etc..... when I start, should I turn the adjustments to each extreme, bring back to the middle and then begin looking  through it? Not good for it?


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## JustUs4All

The farther away the zero the more accurate your shots will be. 

I believe it was Buzz Aldrin who said about the ride to the moon, "If you are off by an inch on landing it is no big deal but if you are off by an inch at takeoff you will miss by many many miles.

Zero at about 225 gets me about 3 inches high at 100 and 2 inches low at 250. 

If you plan to kill at 250, practice at 250 and 350 first.  It will make a lot of difference in your confidence and in your hunting.


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## rosewood

bfriendly said:


> I just got my first .308 so i am glad this came up......looks like I gonna try and set up 1.8” high at 100 with the ammo I got....
> 
> How long to let barrel cool?   Does it matter as long as I’m not shooting round after round?



It really depends on the gun, the weather, the ammo.  A heavy barrel gun heats up slower and is more rigid so you can shoot more before needing to let it cool.  Hotter burning powder will heat up the barrel quicker.   Hotter days, your barrel heats up faster and cools slower (yeah, I know I am captain obvious).

Also, the forearm and anything else that is touching the barrel can affect the groups.  As the barrel heats up, it expands and things touching the barrel can push the barrel one way or the other throwing off accuracy.

You really need to shoot it and make notes on where each shot groups.  If you fire 3 rounds and #4 sails, 3 might be all you should test with.  If you can shoot 10 before you have the flyer, then you can shoot accordingly.  It really is different between different guns.  If you have a hard time remembering, have a target just like the one you are shooting on the bench, draw in each shot where they are impacting on your target so you remember in which order you fired them.

From an accuracy point, I believe the most accurate shooting string would be where the barrel is near the exact same temperature from the last shot, but that is impractical and would require you to measure the barrel temperature.  As for hunting, that is worthless as someone else said, the cold barrel shot is what typically matters when hunting.

Rosewood


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## ssramage

I've been spoiled some in recent years, but it's more complicated now due to distance, but I've always used Eagle Gun Range in Macon to sight in my rifles. They have a 25yd indoor range and a computer ballistics program. I'm usually sighted in with 3 shots total. I confirm it on a longer range and it's always dead on.


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