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Old September 22, 2018, 11:42 AM   #1
eddyq
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Interpreting a ballistics chart

I am reading a 7mm Remington Magnum ballistics chart and don't understand something. Here is an example:

Yards....Drop In Inches(100YD)Zero....Drop in Inches(200YD)Zero
100:....................0..........................................1.8
200:.................-3.6..........................................0
300:................-12.9......................................-7.6

I assume this means you sight it in at 100 yards and the drop is 0" then at 200 yards the drop will be 1.8" (so aim 1.8" high). The next line says you sight in at 200 yards and that drop is 0" and at 100 yards the bullet will be 3.6" high (so at 100 yards aim 3.6" low). Now how do I interpret the 3rd line? Does this mean I sight in at 300 yards and for 100 yards aim 12.9" low and at 200 yards aim 7.6" low?

Last edited by JohnKSa; September 22, 2018 at 02:06 PM. Reason: Corrected chart formatting.
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Old September 22, 2018, 11:58 AM   #2
Mal H
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Looks like you interpreted the lines correctly.

Since the columns are titled "Drop", a rise above the line-of-sight (LOS) would be a negative number.

If you sight in at 300 yds., the arc of the bullet will always be above the LOS at any point before 300 yds. To compensate for that, you would aim the indicated amount below the LOS.
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Old September 22, 2018, 12:00 PM   #3
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Now how do I interpret the 3rd line? Does this mean I sight in at 300 yards and for 100 yards aim 12.9" low and at 200 yards aim 7.6" low?
No.

What it is telling you is that with the rifle sighted for 100yds (hits point of aim at 100yds) then the bullet will be 12.9" low at 300 yds . With the rifle sighted for 200yds, the bullet will be 7.6" low at 300yds.
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Old September 22, 2018, 12:02 PM   #4
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They are using a confusing format.They are giving you the numbers for a100 yd zero,and for a 200 yd zero side by side.

The 100 yd numbers say you can choose a 100 yd zero,or,move your impact up 1,8 in for a 200 yd zero.
If you zero at 100,you will be 3.6 in low at 200
If you zero at 100,you will be 12.9 in low at 300.A 200 yd zero will put you 7.6 low at 300

If you go to Hornady's web page,they have a free ballistic software you can use.

Then you can decide on any sight in distance you want.It might be interesting to look at a 300 yd zero,or a 250
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Old September 22, 2018, 12:05 PM   #5
Mal H
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Not sure about that, 44 AMP. Since the columns were labeled 100 yd and 200 yd, it implies that the figures are for those distances only. If the rifle is zeroed only at 100 yds., then there would be no figure for 300 yds., and the third line would say the drop at 300 yds is less than the drop at 200 yds.

HiBC is certainly correct when he says that's a confusing format.
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Old September 22, 2018, 12:34 PM   #6
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"...Yards Drop In Inches(100YD) Zero Drop in Inches(200YD) Zero..." That's a "Short Range" trajectory chart. Isn't a normal way of charting it though. Usually a 'zeroed at distance'(like 100) and the above zero or drop at other distances by 100 or so yard increments.
The bullet weight at a specific muzzle velocity matters. However, according to that chart if you sight in 'dead on' at 100, you'll be 3.6" low at 200 and 12.9" low at 300. Sight in 1.8" high at 100, you'll be 'dead on' at 200 and 7.6" low at 300.
This might help. A 160 grain bullet out of Winchester factory ammo. Slightly different numbers but close enough.
http://guide.sportsmansguide.com/bal...stics_124.html
This is the parent site of the above.
http://guide.sportsmansguide.com/ballisticscharts/
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Old September 22, 2018, 02:05 PM   #7
JohnKSa
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Quote:
Yards....Drop In Inches(100YD)Zero....Drop in Inches(200YD)Zero
100:....................0..........................................1.8
200:.................-3.6..........................................0
300:................-12.9......................................-7.6
I would take it to mean:

When zeroed for 100yards, the bullet will be at point of aim at 100yds, 3.6" below point of aim at 200yds and 12.9" below point of aim at 300yds.

When zeroed for 200yards, the bullet will be 1.8" above point of aim at 100yds, at point of aim at 200yds, and 7.6" below point of aim at 300yds.
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Old September 22, 2018, 02:11 PM   #8
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If you sight in at 300 yds., the arc of the bullet will always be above the LOS at any point before 300 yds.
Not really, the bullet starts off being about 1.5 inches below the line of sight, and the arced bullet path actually crosses the line of sight on the way up and then again on the way down.
The first zero is usually around 25 yards or so.

Forgetting the fact that the bore is about 1.5 inches below the scope is a good way to destroy a chronograph or something else close that you thought you were shooting over the top of.
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Old September 22, 2018, 02:32 PM   #9
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True - I was talking about practical rifle distances, not very close to the muzzle.

I think John has the best interpretation of that chart. When you see it formatted properly, it makes a lot more sense.
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Old September 22, 2018, 02:38 PM   #10
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The forum software does horrible things to tables that need proper spacing/tabs to make columns readable.

What's odd is that the removal of spaces/tabs isn't done to save storage space--because the original post still retains all the whitespace characters. They are just removed in the display process.
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Old September 22, 2018, 02:49 PM   #11
eddyq
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Since I got so many different answers I did a search and found this: https://www.buckmasters.com/Magazine...llistics-Chart
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Old September 22, 2018, 03:37 PM   #12
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No, you got different explainations of the same thing, except for MalH.
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Old September 23, 2018, 05:28 PM   #13
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Quote:
I would take it to mean:

When zeroed for 100yards, the bullet will be at point of aim at 100yds, 3.6" below point of aim at 200yds and 12.9" below point of aim at 300yds.

When zeroed for 200yards, the bullet will be 1.8" above point of aim at 100yds, at point of aim at 200yds, and 7.6" below point of aim at 300yds.
This.

Don't real left to right, read the columns. The middle column is trajectory with 100 yard zero, the right column the trajectory with 200 yard zero.

It is worth noting, that is probably with a 1.5" sight height, which no rifle I own actually has. You are better off running the numbers in a good ballistics program that allows for things like altitude, sight height, any most things you can think of, and probably some you can't.

I like: http://www.jbmballistics.com/ballist...culators.shtml
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Old September 24, 2018, 02:35 AM   #14
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Eddy;

Everyone is trying to explain your chart the same way. The problem here is that you're trying to read the chart and its information from left to right, but it should be read as columns, such as an X and Y axis like this:https://www.quora.com/What-is-a-hori...vertical-axis#

So, the left column (Y-Axis), reading down reads:

Yards
100
200
300


Moving to the right along the X-axis, the middle column reads:

"Drop In Inches(100YD)Zero," which should mean to the reader, "Drop in inches for a 100 yard zero"

Then reading vertically directly below this heading we have:

0
-3.6
-12.9

Meaning, that at 100 yards (referring to the "100" directly to the far left on the chart) your point of impact (POI) is 0.

At 200 yards (referring to the "200" again to the far left) POI should be -3.6 inches below our POA (Point of Aim)

At 300 yards (far left) POI should be -12.9 inches below our POA.

Going back to the top of the chart and moving right again along the X-axis, we read the heading, "Drop in Inches(200YD)Zero." We again read directly below this heading to see:

1.8
0
7.6

Which should mean to us that at 100 yards our POI is actually 1.8 inches above our POA, or +1.8 inches. At 200 yards, our POI should be 0 (zero), and at 300 yards our POI should be 7.6 inches below our POA, or -7.6, as commonly written on most ballistic charts.

Hope that helps.

Last edited by Rangerrich99; September 27, 2018 at 03:41 PM.
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Old September 24, 2018, 02:21 PM   #15
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Yep. Slightly different.

The problem is, who really cares that the scope is 1.5 inches high etc.

Put the danged thing 2 inches above the X for the group or first shot at 100 and the rest works as advertised. Worked fine when I was hunting.

If you are spot on at 100 yards (center of X) then at 200 yards you are 3.9 low and 300 12.9 low.

Set the scope for 1.8 inches (well call it 2) at 100, you will center hit the X at 200 and be 7.6 inche low at 300.

Sometimes called point blank range you just aim center of Animal (behind the shoulder) and you will hit the kill zone out to 300 yards.
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Old September 24, 2018, 06:33 PM   #16
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It is a place to start, targets do not lie !!!
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Old September 25, 2018, 09:28 AM   #17
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Best solution is to sight-in @ 200. Hold low for close in shots.
Good luck.

May consider getting a laser range-finder.

I use one on a stand and then sweep noting distance for trees to gget good idea of range. all around me.
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Old September 25, 2018, 10:04 AM   #18
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Hopefully not to overly confuse the issue, but the bullet always crosses the line-of-sight twice. Once on the rise & next at its zero range.
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Old September 25, 2018, 10:21 AM   #19
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Its where it hits that is really relevant.
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Old September 25, 2018, 03:14 PM   #20
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There is nothing in those drop chart's that is worth reading. You want to know how much a bullet drop's at a certain distance when zero'd at another? Go zero your rifle then shoot at the other range. You want to know how to get the most from your rifle that it has to offer? learn to use max point blank range. You want to shoot beyond that, MPBR, then your going to have to become a better shooter. Once the bullet drops out of MPBR the onus is on the shooter to make the proper adjustment's, you can't do that by guessing.
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Old September 26, 2018, 07:36 AM   #21
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Being lazy and hating to think when taking a hunting shot, I merely memorized the rudiments of trajectories for the majority of "deer cartridges". This is in the muzzle-velocity range of roughly 2,600 to maybe 3,100 feet per second.

Two inches high at 100 yards makes for a 200-yard zero. Then, around five or six inches low at 300. 18 to 24 inches low at 400, so call it 21 inches. After that it's roughly four feet low at 500.

All I know is that it's worked for me for over forty years of dining on Bambi. Ranges for the kills have varied from 25 yards to 450. And mostly bang-flops, never any tracking.
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Old September 26, 2018, 02:20 PM   #22
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Quote:
Now how do I interpret the 3rd line?

Point of Impact of the bullet will be 12.6 inches lower than the Point of Aim with a 100 yard zero single point zero and the Point of Impact will be 7.6 inches lower than the Point of Aim with a 200 yard single point zero.
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