Using riflescope to figure distance

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Bayourambler

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Tried some long range shooting without the rangefinder for the first time today. Knowing the exact size of target and using the formula I found online, I coming up short with my figures after checking with rangefinder. Usually by around 10%. I'm using a Burris xtr 2 5-25 scope in Moa reticle. Formula used is (size of target in inches) divided by Moa measured in scope x 95.5= yards. This should be right, I get close every time, but always a lil short. Last shot today I figured it up at 630 yds shot and was 6" low. Checked with range finder , 680 yds. Is it better to use horizontal or verticle lines in scope?
 
Is your reticle a 1st focal plane or 2nd focal plane? If it is 2nd, then there is a specific magnification at which the reticle markings are accurate, you have to measure at that magnification. For instance, my Viper HS-T 6x24 scope is 2nd focal plane, the reticle markings are accurate at 18X and that magnification has a detent in the adjustment collar.

www.vortexoptics.com/video/first_vs_second_focal_plane
 
Also your measure event of the target through the scope needs to be very precise. A small misread on the measurement can mean a large miscalculation of distance. Especially at longer ranges.
 
A 10% margin of error is acceptable in sniper school. To me its still not "ok", but remember its SCHOOL. Meaning entry level.
 
Is your scope in shooter moa or true moa? It is 1inch at 1 hundred yards or is it true moa at 1.047" at 100yds
If your reticle is not true moa the it could influence the estimate but not by 10%
 
Is your scope in shooter moa or true moa? It is 1inch at 1 hundred yards or is it true moa at 1.047" at 100yds
If your reticle is not true moa the it could influence the estimate but not by 10%
Hmmmm.. I have no idea. It does make it a lil closer when I multiply x 100 instead of 95.5.
 
It's normal for all scopes to have a small spread in adjustment value compared to what their specs state. Their lenses have a small spread in focal lengths that change target image sizes at their focus points in the scope. The adjustment mechanics to move the inner tube are a compromise and are not exact. All that adds up to a few percentage points error for a given adjustment change per click.

The old Lyman and Unertl externally adjusted target/varmint scopes' clicks were exact for 1/4 inch per 100 yards. Their mounts were on 7.200" centers and each click moved .0005". Four clicks moved the scope .002" which is 1/3600th of 7.200" mount spacing. There's 3600 inches in 100 yards. Didn't matter if the 20X scopes actual magnification was 19.274 times due to its several lens' tolerances.

Hard mount your scope focused at exactly 100 yards on a ruler. Count the clicks to move the reticle exactly 10 inches on the ruler. Do the grade school math to figure it's exact move per click. You'll be surprised.
 
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It's normal for all scopes to have a small spread in adjustment value compared to what their specs state. Their lenses have a small spread in focal lengths that change target image sizes at their focus points in the scope. The adjustment mechanics to move the inner tube are a compromise and are not exact. All that adds up to a few percentage points error for a given adjustment change per click.

The old Lyman and Unertl externally adjusted target/varmint scopes' clicks were exact for 1/4 inch per 100 yards. Their mounts were on 7.200" centers and each click moved .0005". Four clicks moved the scope .002" which is 1/3600th of 7.200" mount spacing. There's 3600 inches in 100 yards. Didn't matter if the 20X scopes actual magnification was 19.274 times due to its several lens' tolerances.

Hard mount your scope focused at exactly 100 yards on a ruler. Count the clicks to move the reticle exactly 10 inches on the ruler. Do the grade school math to figure it's exact move per click. You'll be surprised.

Another method if you dont have a way to hard mount the scope is to take a large piece of paper, space out dots vertically at 1 moa increments.
Ensure your zero is well established for the range.

Hold at the same aim point, the bottom dot for all shots
fire a shot, dial up 1 moa.
Fire a shot, dial up 1 moa,
Repeat until you run out of adjustment. The impacts should match up with the dots all the way up. If you end up missing low consistently, your scope could be off.
If you think you messed up on a shot, shoot it again. Maybe try at 200yds so you wont see the bullet impact the paper

As previously mentioned though, i would imagine an error in range estimation
 
After I used the rangefinder I saw target was actually 675 yds , not 635. My table said my come up was 14 Moa not 12.5. Dialed it in and bullseye. So the actual adjustment is good, it's just the marks on the reticle that seem to be a lil off. I want a more powerful rangefinder but the gun funds are down right now! The one I have now only does around 500 on a good day.
 
Is your scope in shooter moa or true moa? It is 1inch at 1 hundred yards or is it true moa at 1.047" at 100yds
If your reticle is not true moa the it could influence the estimate but not by 10%
Is your scope in shooter moa or true moa? It is 1inch at 1 hundred yards or is it true moa at 1.047" at 100yds
If your reticle is not true moa the it could influence the estimate but not by 10%
Reticles, if graduated MOA, will be a true MOA. Why be approximate?

Estimating MOA as 1" per 100 yards is plenty accurate for anything under 600-700 yards. True MOA would be 6.24 inches = 1 MOA at 600 yards. To say it's 6 inches at 600 yards, I doubt many shooters could detect 1/4" at that distance, much less shoot that close. That estimation error is only going to be 1/2" at 1200 yards, still within most rangefinder errors.
 
Reticles, if graduated MOA, will be a true MOA.
I don't think so. They're all approximate in reality. There's not enough paper on earth to write down all the digits for true and exact MOA amounts; we round them off for ease of use so they are approximate.

Like scope internal adjustments marked in inch fractions, none are exact. Even if the mechanics are exact (rare), a few percent spread across the optics' lenses focal lengths makes target images vary that much on reticles. If the target image on the reticle is a few percent too big, a given adjustment will be the same amount too small.

With almost 5% difference between inch and true MOA at target range, it's possible to have a MOA scope move bullet impact the same as an inch scope.

I've checked many internally adjusted scopes on my benchtop collimator and at range on yardsticks. None so far are error free. Best ones are about 1% in error. A couple were near 7% off. Slop in zooming from low to high magnification often caused 1 MOA or more reticle movement on target.

The best camera lens' optics can have a few percent spread in focal length from what's marked on them.
 
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i've long contended mil ranging isn't practical. it used to be very common part of sniper matches and everyone sucked at it. everyone.
in the past several years, it's really only useful in two situations:
1. to get you in the ballpark so you or preferably your spotter can give you a correction and hit a target on the second attempt
2. when your laser is giving you multiple distances and you have the time to mil the target to see which distance is right. this is fairly common when you have trees or cars or something that appear on either side of the target but that are actually much closer or farther away, or if your target is on top of a hill with another behind it, etc.

with silencerco radius selling for $500 and lots of other decent range finders on the market, the only people mil ranging anymore are doing so out of nostalgia

that said, if you want to be semi-decent at it, here are a few tips
1. measure the largest object you can. your error will be much less significant that way. e.g. don't range the 6" plate, range the 48" piece of rebar it's hanging from
2. practice ranging different shapes (circles, diamonds, squares, etc) and objects of different colors. you may be surprised that you get different measurements on different colored objects
3. never moon a werewolf.
4. poorly designed reticles often have the smallest graduations at the extreme edges of the glass, where distortion is the worst. it may be worth changing magnification or using a part of the reticle near the center. it's not just your glass, but also your vision, if you are for instance, straining to view the top of the FOV
5. get a mildot master and make a mil cheat sheet like the one pictured below. aside from being inaccurate, mil ranging takes forever and you'll miss a chance to pull the trigger if your target wanders off while you're jacking around with a calculator.
6. you basically have to build two stable positions when miling; one to measure the target, then you go to your mildot master or cheat sheet and dope card and then build another position to take the shot. practice not sucking at that. put your dope where you can get it without moving your head off the stock if possible. (e.g. i used a retractable lanyard)
dopecard.jpg
 
Yep it ain't the scope , been doing some practice today and measuring , it's dead on. True moa by the way. It's just tough telling if it's 12.5 or 12.7 etc., at distances over 300 yds!!! my hats off to those who can get it right. I guess my eyes are not that good!! That's why they made laser rangefinders ! Just cool to fool with. It will get you close though. I multiply by 102 instead of 95.5 and get damn close out to 800 yds.
 
For what it's worth, internally adjusted scopes with range focus made adjusting the front objective lens have less change per click at short ranges than long ones. A 1% less change going from 1000 to 100 yards is common. That's caused by the target image at the first focal plane getting bigger as range gets shorter and the objective lens moving forward.
 
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i've long contended mil ranging isn't practical. it used to be very common part of sniper matches and everyone sucked at it. everyone.

A couple of weekends ago I was trying to range ground squirrels from my kitchen window using a Leupold Mark 4 1.5-5x scope with a TMR reticle. They were 80 to 170 yards away and I was shooting a suppressed .22 LR so accurate range was kind of important. Given the hundreds of rounds fired and only one "confirmed" casualty, carried off by a Red Tail Hawk, I was clearly having ranging issues, in part due to the unknown size of the squirrels but also the reticle. The Colombian ground squirrels up here a far from cookie cutter.
 
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