Scope aim question

[clemeister]

Just got my first precision bolt action rifle. After break in I zeroed it at 100 yards, no problem (wish my ar15s were this accurate at 100 ). Looked at ballistics calc to see how much compensation at 200 yards. To my surprise it told me up 4 clicks. Just for shi&s and giggles, I aimed at the bulls eye and shot. The ballistic calc was right, it was low.

My question is assuming the scope's point of aim is on a horizontal plane, the bullet is rising at 100 yards to meet the point of aim. Isn't the bullet still rising at 200 yards? Shouldn't the bullet be above the point of aim at 200? I.e. shouldn't I have to dial the scope down? What am I missing?

 

[usmcmad]

Someone with more technical experience will chime in here. But, No. The bullet is not rising at 200 yards. The bullet never 'rises'. It follows at straight line until it leaves your barrel. At that point gravity takes over. It starts dropping. You are shooting at an angle upwards. At 100 yards it is small arc. If you reticle never changes your arc is the same.

 

[ShtrRdy]

With a 100 yd zero, the bullet rises to a maximum height above ground around the 100 yd distance. Then the height decreases from there.

You can run a ballistic solution with closer data output spacing and get a good idea of the trajectory.

 

[Precision Underground]

Your bullet starts dropping toward the earth as soon as it leaves the barrel. When you zero at 100 you are adjusting that drop to be dead on at 100. Therefore it will drop even more at 200.

 

[Sniper266]

This is best expressed through a drawing, but i will attempt to text through this one.
The relation between the bore axis, the scope and the target can be expressed(drawn) as a less than sign (<)
The scope is angled down, the barrel is angled up and the target is the point of intersection

When the round is fired the bullet races through the barrel and out the muzzel. Because the barrel was slightly angled up, at some point the bullet will intersect with the line of sight of the scope.

We zero our scopes so that the rising bullet insects with the line of sight of the scope on the target at a certain range.

When the scope is dialed up for elevation. You are adjusting the angle and ultimatky the point at which the bullet will cross the scopes line of sight.

I hope this helps

 

[Precision Underground]

This is best expressed through a drawing, but i will attempt to text through this one.
The relation between the bore axis, the scope and the target can be expressed(drawn) as a less than sign (<)
The scope is angled down, the barrel is angled up and the target is the point of intersection

When the round is fired the bullet races through the barrel and out the muzzel. Because the barrel was slightly angled up, at some point the bullet will intersect with the line of sight of the scope.

We zero our scopes so that the rising bullet insects with the line of sight of the scope on the target at a certain range.

When the scope is dialed up for elevation. You are adjusting the angle and ultimatky the point at which the bullet will cross the scopes line of sight.

I hope this helps

The bullet is never rising. I see what you are trying to say but that is still not what is happening. If you were to put a target with the bullseye right up the the end of your barrel the bullet would hit the center of the bullseye. Move the target 10 feet away in the exact same spot and your bullet will now hit low, not much lower or even enough to measure but it would be lower. Now move the target 100 yards away in the exact same spot and the bullet will hit lower, plenty enough to measure. All you are doing when you zero your scope is lowering the point of aims down enough so that you raise your barrel enough to compensate for how much the bullet will drop at the zero distance.

 

[Sniper266]

Jogolffl. I agree. And maybe i just expressed it wrong. To clarify; the reticle in the scope and in some cases the scope base are at a down ward angle when the barrel is level. When looking at the target the bore axis is now angled up. This sends the bullet “up”. The bullet will rise to meet the line of sight of the scope.

 

[clemeister]

Thanks for the replies. Not to belabor the point but I've seen videos of 50/200 yard zero (like this one ). I guess the bullet is still rising at 50 yards and not at 100? I'm assuming the bullet is crossing the point of aim twice on the way up at 50 and on the way down at 200

 

[Diver160651]

Remember when shooting, the scope's reticle is NOT what is angled, it is the barrel. Think of thinking of it the other way is sure to mess you up.

I think the confusion comes from the near and far zero used with high SOB at short range like a service rifle. The 25 or 50m zero creates a fairly acute angle between the bore and sightline. The acute angle of the bore tilted upward to meet a 25m target in a sight that is 2.5" over bore, has the bullet crossing the sightline at the 25m, while gravity is technically still causing the bullet to drop, it is continuing it's angled path above the LOS until it's max ord for that close range zero and coming down back THRU the far zero.. This results in hold UNDERS and holdovers. Pushing our zeros further out to 100, lines things up better so that we more or less take that entire process out of play.

For a 25 zero and AR height the far zero is generally a hair past 300yards, for a 50 just under 200, etc.. as you reduce that super acute angle needed by zeroing at 100, you don't get as extreme of results, and for all practical purposes everything becomes a hold over.

But that entire battle zero is kinda lame for PR..

Just watched the video, hilarious, love the lead sled I need one.

 

[supercorndogs]

Just like open sights. You turn your front sight up, this moves where your barrel is pointing lower, POI moves down.

 

[Prebanpaul]

Do your self a favor. Go to you tube. Type in search engine MOA and a guy with a blue screen will pop up. Watch that video three or four times. You will then see what all these guys are talking about.

 

[Diver160651]

Here is a quick printout I ran for you from ColdBore, all the same except for the near zero. Hope this makes it easier to understand, why the 100 zero is better and doesn't end up higher at 200.

PATH:
Red is 100y, Blue is 50 and yellow is 25y. The light blue vertical line is the 100y crossing. For all practical purposes, the 100 zero's near and far are the same.

DROP:
Notice the the "Drop" is the decay of the bullet that takes place the minute the bullet leaves the barrel. This happens regardless of the angle of the barrel for the zero set.