# Learned something new today.



## Panache (Feb 17, 2011)

This happened while I was sighting in the new rifle (DPMS LR243). I bore sighted the rifle, checked the ballistic tables from the ammo manufacturers, then went to the range and set the target at 25 yards. I got ok groups so I moved it out to 100 yards. It should have hit about 2 inches high. No holes in the paper at all. Thought I was just not holding right/tight. Went home and thought. Went out second time to range. Started out at 25 yards. Again a good group about .5" high. Right where the ammo maker said it should be. Moved it out to 50 yards. Group about 4" high. Then on out to 75 yards. Group about 6" high. Lowered the crosshairs about 20 clicks and went out to 100 yards. This time it was on the paper. The second 3 shot group was posted here the other day.

While killing time cleaning firebreaks today it occured to me the scope might not be the industry standard of 1.5" above the bore. I came home and measured the height of the scope and it is 2.5" above the bore.

I then looked up a ballistics calculator that allowed me to put in the sight height and found out I was off by about 1.5" at 25 yards. This equals 3" at 50 yards and 6" at 100yards. That was the cause of the first try at 100 yards not being on the paper.

Lesson learned: Do NOT assume just cause it was that way before it will always be that way.

Jeff
AKA Panache


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## youngdon (Mar 10, 2010)

A good reminder Panache.


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## knapper (Feb 5, 2010)

It is always important to know how high the scope is above the bore as you found out, good lesson.


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## bones44 (Jan 7, 2011)

I use a Leupold Boresighter. It's adjustable for height so when you look through and don't see anything it's not center. One of my best investments ever. Good luck !


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## bowhunter1 (Jan 22, 2012)

When I bore sighted my 30-06 I used a balistic chart to find out where my bullet should hit at 25yds then I took a piece of paper put a black dot on it then put a second dot on it where the chart said I should hit at 25yds. Then I looked through the scope put the boresite red dot on the dot where the bullet should be hitting then adjusted scope to get the cross hairs on the other dot. It put me with in 2 inches of where I should be at 100yds. But like you learned I calculated in my scope height also.


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## All-Around-Outdoorsman (Feb 7, 2012)

I use a ballistic calc app for my phone and it works great but before you do a quick calculation you must type in grain of bullet,fps, click value, temp, height of sight, and a bunch of other simple variables and it seems to work of for super long shots. (500+yards) Lots and lots of variables that go into long range shooting i also had this problem but i went home very confused and did my homework and now it all makes cents


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