308 zero

cmil84

New member
I seen a post on here about how guys would zero there 223s at 50 yards and it would be the same as a 200 yard zero. I was wondering if there was a method like this for the 308. I just recently got a 308 and dont know a whole lot about the round. I know the military uses it in there sniper rifles and I know its a very popular round. I know it has an effective range of 800 meters and I know people have shot it out to 1000 yards. I want a 200 yard zero. Any advice would help thanks
 
There are two points that the bullet passes the line of sight. Once on the way up to the peak of its arc, the second on the way back down. The first point where it crosses the line of sight is referred to as the close range zero.

The catch is that every bullet flies a little different and different barrel lengths will produce different velocities. Different velocities will produce a different trajectory (arc) moving your close range zero point forward or backward relative to your distant zero range. After you have the velocity of the bullet and the ballistic coefficient for the bullet, you will also need the height of the sight above the bore to accurately compute your trajectory to get a close range zero.

Long story short: If you have 200 yards in which to shoot, zero at the 200 yards. You can use a close range zero to get on paper at longer distances, or to make sure you windage is dialed in. But otherwise, there is no replacement for shooting at distance you want to zero at.

You also have to recognize things like pronounced parallax occur with scopes at very close ranges unless you have an adjustable objective. Basically, with parallax it causes the reticle to move around on the target. You can see this when aiming by moving your eye up and down and side to side. If the gun is bagged or otherwise not moving, you will still see the reticle move around on the target. This can easily throw a round an inch off. An inch off at a close zero can put you way off at your distant zero.

For irons, however, the close zero can work well as it is easier to see the target (especially with older eyes), and the parallax is a non-issue. But you still want to check it at range.

 
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Even though one can look at tables $ theoretically figure out an impact point at longer range, I think it's almost essential to do some shooting further out.

The 308(and it's family members) is one of my favorite rounds. It was a military mainstay as a sniper round a ways back. It seems current chamberings have moved on from the 308, more variety. In the book, "American Sniper", the author normally used a 300 Win mag. There were others at times, like the 50 cal.

Other areas of consideration are loads/bullets, optics & maybe a trigger improvement, from stock. I'm more a hunter than a long range shooter, but quality, higher power optics can really make a difference.
 
Originally Posted By: BroncoGlennThere are two points that the bullet passes the line of sight. Once on the way up to the peak of its arc, the second on the way back down. The first point where it crosses the line of sight is referred to as the close range zero.

The catch is that every bullet flies a little different and different barrel lengths will produce different velocities. Different velocities will produce a different trajectory (arc) moving your close range zero point forward or backward relative to your distant zero range. After you have the velocity of the bullet and the ballistic coefficient for the bullet, you will also need the height of the sight above the bore to accurately compute your trajectory to get a close range zero.

Long story short: If you have 200 yards in which to shoot, zero at the 200 yards. You can use a close range zero to get on paper at longer distances, or to make sure you windage is dialed in. But otherwise, there is no replacement for shooting at distance you want to zero at.

You also have to recognize things like pronounced parallax occur with scopes at very close ranges unless you have an adjustable objective. Basically, with parallax it causes the reticle to move around on the target. You can see this when aiming by moving your eye up and down and side to side. If the gun is bagged or otherwise not moving, you will still see the reticle move around on the target. This can easily throw a round an inch off. An inch off at a close zero can put you way off at your distant zero.

For irons, however, the close zero can work well as it is easier to see the target (especially with older eyes), and the parallax is a non-issue. But you still want to check it at range.



I agree with this in that you should always zero at the distance you want to be sighted in at. You will find that different ammo based on different BC of the bullet and different velocity will not shoot the same comparatively at different distances and won't "match up" at a short and long range.
It is incorrect, however, that a bullet "passes the line of sight twice." The "peak of its arc" is the muzzle. As soon as that bullet leaves the barrel gravity is pushing it downward. It never gains elevation. Your sight device, be it iron or scope, must align with the bullets path and that is what you are trying to coordinate to the trajectory of the bullet. Technically you are angling your rifle upward to create an "arc" because your sigts are above the plane of the bullet's travel.
Semantics I suppose, and BroncoGlenn is otherwise spot on. I'm probably picking the fly crap out of the pepper, but I heard another guy at the range the other day trying to explain this and was telling some new shooters how the bullet gains elevation and then drops after time. It was confusing and I thought I would just take an opportunity to clarify.
 
The close zero works well to get you on paper for your actual zero if you have issues finding holes to start with. After you're on paper, tune as needed. It's pretty much the same as bore sighting, it's the start not the finish line.
 
Originally Posted By: IdahoelkaddictOriginally Posted By: BroncoGlennThere are two points that the bullet passes the line of sight. Once on the way up to the peak of its arc, the second on the way back down. The first point where it crosses the line of sight is referred to as the close range zero.

The catch is that every bullet flies a little different and different barrel lengths will produce different velocities. Different velocities will produce a different trajectory (arc) moving your close range zero point forward or backward relative to your distant zero range. After you have the velocity of the bullet and the ballistic coefficient for the bullet, you will also need the height of the sight above the bore to accurately compute your trajectory to get a close range zero.

Long story short: If you have 200 yards in which to shoot, zero at the 200 yards. You can use a close range zero to get on paper at longer distances, or to make sure you windage is dialed in. But otherwise, there is no replacement for shooting at distance you want to zero at.

You also have to recognize things like pronounced parallax occur with scopes at very close ranges unless you have an adjustable objective. Basically, with parallax it causes the reticle to move around on the target. You can see this when aiming by moving your eye up and down and side to side. If the gun is bagged or otherwise not moving, you will still see the reticle move around on the target. This can easily throw a round an inch off. An inch off at a close zero can put you way off at your distant zero.

For irons, however, the close zero can work well as it is easier to see the target (especially with older eyes), and the parallax is a non-issue. But you still want to check it at range.



I agree with this in that you should always zero at the distance you want to be sighted in at. You will find that different ammo based on different BC of the bullet and different velocity will not shoot the same comparatively at different distances and won't "match up" at a short and long range.
It is incorrect, however, that a bullet "passes the line of sight twice." The "peak of its arc" is the muzzle. As soon as that bullet leaves the barrel gravity is pushing it downward. It never gains elevation. Your sight device, be it iron or scope, must align with the bullets path and that is what you are trying to coordinate to the trajectory of the bullet. Technically you are angling your rifle upward to create an "arc" because your sigts are above the plane of the bullet's travel.
Semantics I suppose, and BroncoGlenn is otherwise spot on. I'm probably picking the fly crap out of the pepper, but I heard another guy at the range the other day trying to explain this and was telling some new shooters how the bullet gains elevation and then drops after time. It was confusing and I thought I would just take an opportunity to clarify.

Your clarification is confusing. The bullet does gain elevation due to the angle of the rifle, it does cross the line of sight twice, and the apex isn't at the muzzle at least not usually.
 
Yeah, I suppose I was making a point more to the argument I heard at the range that the bullet "climbs" or gains elevation. If the rifle were to be perfectly flat/level, the bullet is falling and does so the entire time. We angle the rifle up as you say, and are more or less angling the sights downward so the two lines intersect where we want.
Sorry.
 
What everyone else said - zero at 200 yards. However, to get close enough to be on paper at 200, A 50 yard zero will get you pretty close. Your results will vary depending on how high your scope is mounted, the weight of the bullet, length of the barrel, etc., but not by a lot.
 
Go to almost any of the ballistic programs on-line to help answer your question.

If you've put a scope on your rifle, chances are that a beginning sighting in at about 25 yards, will put you at least on paper at 200

Since you've already discussed the double crossing of the line of sight, I'd recommend playing with a ballistic program to determine a zero that will allow you to maximize your shooting distanes while keeping your bullet a certain distance above and below that line. For example, could a 250 yr zero give you a maximum above line difference of say 3" ahead of 250, and a drop past 250, say at 300 of -3" as well. This will allow you to shoot with more confidence over a longer range and never be higher or lower than what ever distance you desire.

Of course, with good study, range time and a modern scope you can learn to reset the zero using the scope, for different distances, and be spot on.
 


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