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Old July 5, 2019, 06:59 PM   #1
'88Scrat
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Join Date: July 11, 2011
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100 Yard Range Restrictions

I no longer have access to a range over 100 yards but have several rifles that I've always sighted in at longer distances or have optics ranged in meters.

For example I have a couple M1 Garands fresh from the CMP that I was planning on getting sighted in tomorrow but in the past have always gotten dialed in at 200 yards counted the clicks down and had my drum line up with the correct range markers almost perfectly.

Another example is my M16A4 build I was gonna take tomorrow as well. The TA31RCO-A4CP ACOG I have on it is ranged in meters but since I cannot move the berm or drop back another 9 yards (100 metere = 109 yards) behind everyone else at the range to get to 100 meters I'm not sure what do to. My first guess is I could probably eyeball it. I THINK I should be about 1/2" high or maybe just under at 100 yards using the 100 meter chevron and 62gr XM855 but I'm not sure.

Any advice?

Thanks!
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Old July 5, 2019, 09:37 PM   #2
Zacf16
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This ballistic software can show you where the bullet will impact at 100 when it is sighted for 200, etc.

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
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Old July 6, 2019, 06:58 PM   #3
pblanc
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With a 16" barrel and M 855 I would plan to zero about 0.3" high at 100 yards for a 100 meter zero.
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Old July 13, 2019, 04:34 PM   #4
Unclenick
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'88Scrat,

Below is a link to my M1 Garand targets for 100-yard sighting. There are three bull's-eyes that are regulation reduced range size for zeroing at 200, 300, and 600 yards. The fourth page is an extension that is taped to the third (MR-31) target to give you the 600 yard zero impact points.

That said, in general, you will find you typically come up two clicks on the elevation knob to go from 100 to 200 yards, two or three more (depends on light and your eyesight) to go from 200 to 300, and then another 11 or 12 (also depending on light conditions and your eyesight) to go from 300 to 600. Also, once you have your 100-yard zero, count how many clicks on the elevation you have to go down before the sight rack bottoms out. It'll most likely be 9, 10, or 11. I've seen all three on different guns. Write the number on a piece of paper and stuff it into the cleaning kit hole in the stock. Once you know this number, you can always find your way to a correct zero from an unknown point by running the elevation all the way down and counting back up.

Mark where your 100-yard zero windage position is on the engraved scale with some white-out or white paint so you can find it again, too. Note that you can loosen the front sight set screw and slide the front sight to force zero windage when the sight base engraving lines up with the middle receiver windage engraving, but this is a delicate adjustment and typically requires a micrometer to do accurately.

Personally, I find I have to add two clicks at 200 just for offhand and bring it back down for sitting rapid, and I have to add 2 clicks right windage when I settle in at 300 for prone rapid. But this is just for my eyesight and anatomy and how I hold. I have to do the same with the AR. You'll find these kinds of personal quirks out as you go along.

The same elevation numbers work for the AR to 300. At 600 they may work. It depends on your cartridge and bullet.

Target link.
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