Sorry for this noob question, but I'm just too dang tired to figure this out.  I'm totally missing something simple or looking at it wrong.  I was messing around with my Remington XCR Tactical Compact 308.  I wanted to see how some hunting rounds compared to my 168 gr FGMM.  So I looked at the following site below to see what trajectory looked like for the Remington core lokt ultra 150 gr to help me get in the black quicker at the range.  I then looked at the JBM ballistic calculator just to compare.  

So here's my question:  On the remington ballistics chart, it shows a long range and short range trajectory.  I read it to say that for short range, if you zero at 100, then you'll be about 4 inches low at 200.  But if you zero at 200, your about 2 inches high at 100.  This just seems like a contradiction to me for some reason.  According to the short range, shouldn't I be able to (if their info was correct for my specific situation) put a group 4 inches high at 100 and be on for 200.  But long range says I should only be 2 high at 100 to be on at 200.  Why? I just don't see why it's different.  I'm totally missing something, probably to do with zeros.  

Anyway, just from shooting yesterday I put it 4" high at 100 and it's on at 200.  So I know what it is for my rifle, I just can't figure out the theoretically difference.  Thanks for the help.  


http://www.remington.com/ballistics/results/default.aspx?type=centerfire&cal=33

Setup: Remington 700 XCR Tactical compact 308 with SS 10x42, mark 4 base and rings, scope 1.75" above centerline

Anyone?

Think of it like this: the zero point is at the top of the bullet flight. If the weapon is zeroed at 200, the round is still traveling up at 100. When the weapon is zeroed at 100, the bullet is on its downward path.

The bullet is actually always dropping from its original trajectory.  Think of the bullet like a cannonball.  It flies in a parabolic arc.  The "zero" is where your sights cross through the trajectory (usually in two places, but sometimes only once).  You also need to factor in that the bullet slows the farther it gets.  This increases the rate of drop over distance.  

Try playing around with this: http://ballisticscalculator.winchester.com/
It gives a nice graphical representation.

The best site for trajectory data is JBMballistics. Go there, and play around. Make sure to get your sight height correct because that plays a big role in trajectory.

if you don't know what it is, measure from the center line of the bore to the center of your optic.

If you really like the 168gr SMK, then look at the 165gr SGK ( Sierra Game King ), it will be very, very close in trajectory. You will still need to shoot it, as it might be a tad off from the charts, and it might shoot left or right of POA when zeroed for the SMK. That goes with any ammo. Always confirm at a short and a long distance.

You're thinking in the wrong units.  You're thinking in inches when you should be thinking in angles, or, more correctly, minutes of angle.

A minute of angle is 1/60th of a degree.  If you draw a triangle between your point of aim and point of impact, and it has a angle of one minute of angle (MOA), the distance between point of impact and point of aim will be about 1" (It's not exactly 1", but pretty close).  This is very convenient, and you can remember 1 MOA = 1" per 100 yards.  We use MOA because an angle of 1 degree would produce a different between point of aim and point of impact of around 5 feet.

So, at 100 yards one MOA (minute of angle) gives a distance of about 1".  At 200 yards one MOA is about 2".  So in your rifle's theoretical case:  A 100 yard zero produces a shot two MOA low at 200 yards, and a 200 yard zero produces a shot two MOA high at 100 yards.  Either way it's 2 MOA.


By the way, you did know that your rifle is has two "zeroes", right?

The bullet begins to slow down and drop as soon as it leaves the barrel.  Therefore, if the sights are horizontal, you have to point the muzzle upward to get the bullet to intersect the sight line.  This means that a rifle is always zeroed in two places.  The first, or near zero, is where the bullet first crosses the line of sight on the way up.  Then the bullet reaches the top of its arc at a point called the maximum ordinate, and starts to fall back to cross the line of sight again at the far zero.

What runnerman said.
Keep,em flying!

Yes, a 100yd zero will have drop data lower than the point of aim after 100yds.

Yes, a 200yd zero will have the point of impact higher at 100yds, and lower after 200yds.

Any zero will have the trajectory lower than the zero before and after the zero range, because the trajectory is an arc.

This!   OP, this is why many people recommend setting your zero at 100yds.  That way you never have to go -0 on your adjustments.