MOA Question and long distance Zeroing

Barks

Barks

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I'm looking for more of a confirmation here...so here is my issue.

I know my handloads average 2970fps out of a 26 inch 7 twist .223. using a Hornady A-max bullet with a BC of .435.
With using several online ballistic calculators, I got an average drop of 360.7 inches @ 1000 yards.

Regardless of zeroed distance, 600yd, 700 yd etc, I find my real world data to impact several inches high on the target when I dial in the recommended "clicks" into the scope.

My question is...is this when the true MOA measurement of 1.047 takes over the "one inch" measurement. If I used the drop of 360 inches @1000 yards, then its 144 clicks to compensate for the drop (36 inch moa) according to the online calcs.

But my scopes are all calibrated in moa adjustments not inch adjustmants, so this 36 if devided by 1.047 is 34.4 moa in reality. This would stand to reason why my bullets always impact high. This difference is 6 clicks @1000 which translates to 15 inches. thats over a foot high.

Am I off the charts here, or does this sorta make sense??
 
Sorta makes sense, but there are other considerations.

have you shot at 100 yards and shot a group, then rasied sight 10 miniutes (40 clciks) and shotanother group, them oved left 10 minutes to try again?

Then measure the actual group movement. Seldom if it 10 inches.

I have fireed hundreds, if not thousands of sighting shots at 1000 yards. I would have been delighted to have a bullet land only 15 inches hi or low. Atmospheric pressure (or density altitude) changes daily, and at 1000 yards that can account for a couple of feet shift. I have seen a 18" shift over a 1 hour match, as a low pressure moved in.
 
I shoot the same bullet at the same velocity and pipe length is the same as yours but I noticed in your post you listed the BC of this bullet as .435.

I use the Ipod FTE ballistics program and it list the G1 curve for the 80 A-max as .453 which gives me a drop of 315 inches at 1000 yards using standard temp and humidity.
 
It is possible your scope is not exatly calibarted at .25 MOA.
As mentioned above, @ 100 yards on 4 Ft paper draw a verticle line, Starting from the bottom shot a group, click up 10 MOA shot again. do four groups measure the distance between in each group. (keeping the same point of aim at the bottom)
 
+1 on your scope's "minutes" probably not being exactly one "minute". If this matters to you, test it at 100 yards, But:

- actually measure the distance from you rifle to the target - "100m" at the range I was using turned out to be 95m, which was not a problem, once knew what it actually was.

- Put up the biggest piece of paper you can find, and put a 1" square black patch near the bottom. For a group (3 or 5 shots) at it, using your 100y sight setting. On the target, write down the scope's elevation setting for that group

- don't come up 10MOA, come up as much as you can and still be on paper (if you have a 3' high piece of paper, come up 30 minutes on your scope). Fire another group, then write the scope's elevation setting r this group on the target.

Go home, measure the actual distance between the centres of the two groups, and do your math (if you don't know how to do the math, post here the actual distance to the target, the number of scope minutes raised, the actual distance between the two groups, and the size of each group, and I can run the numbers)
 
Scope height above the boreline can affect how the scope 'sees' the target.

consider using a G7BC instead of the G1.

Shoot at other distances and see if the error is consistent. Then just adjust your drop chart accordingly until the scope, rangefinder, and chart WITH THAT LOAD match.

I have an article on my site that can help. Rarely does a drop chart agree with my real world shooting but it is close enough to get me on paper.

Jerry
 
Thanks to all who replied.

The bullet used is indeed the 75 grain Amax. I see I failed to mention that.
Scope is a Leupold VXIII 8.5-25 x 50. TPS Medium hight rings. My scopes are always zeroed @ 100 yards and the turrets set back to "0" before I shoot. I base all of my shooting from a 100 yards zero.

My goal is to always know what I need to set my scope at to zero at any distance I shoot at......and in time with practice, this will become second nature. I was just having a hard time with long range sessions where without a spotter, I would just start at 600 yards......dial in what the ballistic calculators "recomended" and expect to be on paper, when in fact every time the POI was over the top of my target stand. Drive downrange only to discover....NO HOLES. I would crunch the numbers again only to get the same number of clicks and then shooting results. I was trying to push my skills farther than they had been developed. Starting at 100 yards and incrimentally working out in 100-200 yards distances at a time makes so much more sense, but OOHHH Noo, I have to do it the hard and frustrating way and just start way out there. :redface:

When I finally brought a friend along, he noticed the shots landing high and we could work from there. Thats when I noticed that at every zeroed distance, all my data from the calcs put my POI consistantly high.

You read over and over that moa=1 inch at 100 yards and 10 inches @ 1000, when in fact 1 moa is 1.047" @100 and 10.47"@ 1000. My basic math was to take my drop in inches(360) and devide that by the distance I was shooting (1000) giving me .36 which represented 36 moa of up required to hopefully put that bullet inside a 1 moa POI. I would dial up 36moa and POI would be over the target. I figured something must be wrong with my scope or my math. Thats when it dawned on me that the scope moves in moa and yes, at closer ranges we can use the word"inches" to represent the scope adjustments, but when I re-do the math 360 devided by 1.047 = 343.8 If I use this number devided by the distance I am shooting (1000 yards) I get a come up value of .3438. And low and behold, 34.3 minutes of up puts me on target, not OVER it like 36 minutes did.

The difference at that distance is 16 inches, add to that the fact that only on the most perfect condition days can I hope to hold a 1000 yard 10 inch group (16 + 10.47) I am out to lunch guessing by over 2 feet. :confused: I do have a drop chart.....a newer revised drop chart that is. I needed to know if I was second guessing myself with the math.
 
I can see why you might have had problems with misses at 1000y - you're never any more than 3.5 MOA away from missing the target at 1000y! ;-)

But I really don't understand why you would have been shooting over the target at 600y. All of the factors contributing to a miss, are less of a factor at 600y than 1000y (the centre of the target is 6 MOA from the edge, you're only coming up (say) 15 MOA from a 100y elevation, the effects of wind, temperature, altitude etc are much less, errors in bullet BC contribute less).

Now that you have gotten things figured out, what are your actually scope elevations for (100y,30,600y,1000y), an how do they compare with what your ballistics program predicts? Have you been able to (mostly) reconcile what is going on?
 
I for one have never found a ballistics program that could put me in the V-Bull at 1000 from 100. I always base my come-ups on the notes I make.

ES, bullet lots, localized variations in mirage, humidity, temperature etc. all affect real-life bullet impact. The fact that the BC changes as it changes speeds also affects POI, but the G7 standard is a big improvement on this.
 
Barks said:
My question is...is this when the true MOA measurement of 1.047 takes over the "one inch" measurement. If I used the drop of 360 inches @1000 yards, then its 144 clicks to compensate for the drop (36 inch moa) according to the online calcs.

But my scopes are all calibrated in moa adjustments not inch adjustmants,
Click to expand...

So you don't have a problem. Read the drop in MOA off the table. There is absolutely no need for 1"=1MOA, it is off by 5%. Don't even think about 1.047.
Scope clicks may not be 100% mechanically accurate either.
 
As mentioned before, atmospheric pressure will affect bullet flight as well so just because one day 100m to 300m was 5.6MOA does not necessarily mean the next day/week/month it will be exactly the same, and it probably won't be unless atmospheric conditions are exactly the same as the day/time of day you took your measurments.
 
Barks said:
With using several online ballistic calculators, I got an average drop of 360.7 inches @ 1000 yards.
Click to expand...

If this is with a 100 yard zero you might need to look at online ballistic calculators that give more mainstream results.
*Eskimo is -339.0", GunSim is -339.0". I may be missing something in my data input of course :).
+1 on atmospherics. Also rangefinding has to be 100%


* Edit: Had distance to chrono at 10 yards, changed it to zero yards.
 
Last edited:
Barks said:
I'm looking for more of a confirmation here...so here is my issue.

I know my handloads average 2970fps out of a 26 inch 7 twist .223. using a Hornady A-max bullet with a BC of .435.
With using several online ballistic calculators, I got an average drop of 360.7 inches @ 1000 yards.

Regardless of zeroed distance, 600yd, 700 yd etc, I find my real world data to impact several inches high on the target when I dial in the recommended "clicks" into the scope.

My question is...is this when the true MOA measurement of 1.047 takes over the "one inch" measurement. If I used the drop of 360 inches @1000 yards, then its 144 clicks to compensate for the drop (36 inch moa) according to the online calcs.

But my scopes are all calibrated in moa adjustments not inch adjustmants, so this 36 if devided by 1.047 is 34.4 moa in reality. This would stand to reason why my bullets always impact high. This difference is 6 clicks @1000 which translates to 15 inches. thats over a foot high.

Am I off the charts here, or does this sorta make sense??
Click to expand...

Based on the info you provided....here is what JBM came up with:

Untitled.jpg


This is with standard settings at 0 Elevation (Sea Level), not knowing your range elevation, proper humidity, temp etc....these also can/will change the numbers significantly.

Running the same numbers but changing Elevation to 5000ft it shows a 3moa Difference at 1000yds which equates to 42" less drop than at sea level:

Untitled2.jpg



The output of the drop charts is only as good as the info you put in.....remember....GIGO (Garbage In Garbage Out)
 
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