Help with scope adjustment question for longer range

M

Mrgunslinger

Guest
I am shooting a custom 6 BR.
I am shooting Berger 95 VLDs at 2960 FPS.
With a 300 yards zero I am wanting to get on paper at 600 yards.
Point blank tells me that the drop from 300 to 600 is 52.67 inches.
My scope is a 1/8" click per inch.
So I come up with 39.5 clicks to get on at 600 yards.
Does this sound right to you?
I will be practicing later this week and will find out for sure but thought I would ask first.
Thanks for your help and knowledge!
 
Mrgunslinger said:
I am shooting a custom 6 BR.
My scope is a 1/8" click per inch.
Click to expand...
No, your scope is not 1/8 inches per click. In this case, " stands for "Minutes of Angle", or MOA for short.

Rule #1 when shooting mid range (and beyond): STOP THINKING IN INCHES.
Rule #2 when shooting mid range (and beyond): STOP THINKING IN CLICKS.

Your scope adjustments are not calibrated in inches, but usually, in some form of angular measurement. Normally, these are MOAs, but could also be mils (any of 5 versions of them).

So, how does one convert from inches to MOA?
  1. A crude approximation (accurate within 5%) is dividing the change (in inches) between yard lines, then dividing by the range to target (in hundreds of yards). At 600 yards, your 52.67 inch change becomes 8.78 MOA. Multiply this change by 8 (8 clicks per MOA), and you get 70.23 clicks. For better accuracy, divide the drop by 1.047 before dividing by distance (in hundreds of yards). This gives a change requirement of 67.6 clicks - so round up to 68. (No such things as fractional clicks on riflescopes.)


    Formula:

    Zero change = Drop (in inches)/1.047/distance to target (in 100s of yards)

  2. Use a ballistic program that converts required changes to MOAs. One of the better ones available (and free) is JBM Ballistics, available at http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi.
    Using JBM's ballistic data for the 95 grain VLD (titled "VLD Litz" - and this is accurately measured data), you get 8.5 MOA of drop. Multiply this by 8, and you get 68 clicks.

If you have an experienced shooter (someone who has shot at distance for more than a year or two) practicing or shooting with you, have them watch the trajectory of your rounds (the "trace" and the "splash") when you shoot. Based on this information, they can give you corrections to get you centered up.
WARNING: While it is possible to "walk" shots onto target using the spotter method, doing this for more than 3 or 4 shots is not advisable, especially if shooting on ranges near populated areas. Why? Ricochets (from "shorts") and misses (from too much elevation) have to land somewhere, and it is hard to predict where this may occur.

Hope this helps.
 
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A little more information....1 MOA (minute of arc, minute of angle, or arcminute) = 1/60 degree
(A circle can be divided into 360 degrees, each degree into 60 minutes, and each minute into 60 seconds.)
Since clicks are a form of angular measurement, and scope settings are changed by counting them, why not just tape a chart with your come ups for various distances, in clicks, to the butt of your rifle, and skip MOA altogether (except for the calculations needed to create the chart)? Being able to zero your elevation knob a the shortest distance that you will be adjusting to really helps as well. We discovered this feature on a friend's Leupold MK IV when we were setting it up for a hunt. It really is handy to know that if you crank your scope all the way down, that the stop is at your shortest yardage zero. Verifying that your scope's clicks are actually what the manufacturer says that they are is also a great idea, particularly if you intend to use a wide range of adjustment.
 
Asa Yam said:
No, your scope is not 1/8 inches per click. In this case, " stands for "Minutes of Angle", or MOA for short.
Click to expand...

Asa i am not trying to hijack the thread but educate me on how you know it is moa and not inches as the make of scope is not known just the amount of adjustment. and i will agree that few scopes will adjust exactly what they say they will due to slight differences in (ie.. thousands of an inch) internal parts size. but some are "supposed" to be in inches and others in moa.
 
earl39 said:
Asa i am not trying to hijack the thread but educate me on how you know it is moa and not inches as the make of scope is not known just the amount of adjustment. and i will agree that few scopes will adjust exactly what they say they will due to slight differences in (ie.. thousands of an inch) internal parts size. but some are "supposed" to be in inches and others in moa.
Click to expand...

He was confident in that statement because ALL scope adjustment knobs are in "MOA", not inches; no matter what the brand. Some shooters just turn this term into inches because it's mentally easier and...doesn't matter for short range shooting.

virg
 
i think not. they may be now but i do have scopes that are in inches. feast your eyes on the picture. notice the inch mark after 1/8 as in 1/8" without the inch mark i would say it was moa.
 

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Earl,

That is NOT an inch mark. As stated in the first sentence in my original post above, the " symbol stands for "minutes" or "minutes of angle". Still don't believe me? Try this experiment sometime:

  1. Obtain a 100 yard rimfire target (the one w/ 3 large bulls arranged vertically.) Set it out at 200 (or 300) yards.
  2. Aiming at the top target, shoot a group using a 100 yard sight setting. (Don't worry about shots being low, we want this to happen. This is why we're using this target.)
  3. Measure the distance in inches between the group center, and the center of the top target. Record this number.
  4. Multiply that difference by 8 (the "number of inches per click", as you state).
  5. Move your scope up by that many clicks.
  6. Fire another group.
  7. Record where your shots landed. (i.e, in the center, above it, or below it?)
  8. Return to your 100 yard zero.
  9. Divide the difference in inches (which you recorded above) by the range to target (in 100s of yards).
  10. Multiply this number by 8 (the "number of MOA per click", as I state).
  11. Move your scope up by that many clicks.
  12. Fire another group.
  13. Record where your shots landed. (i.e, in the center, above it, or below it?)
  14. Return to your 100 yard zero.
Best guess says the group for Item #13 will be closer than for #7.
 
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Asa Yam said:
Earl,

That is NOT an inch mark. As stated in the first sentence in my original post above, the " symbol stands for "minutes" or "minutes of angle". Still don't believe me? Try this experiment sometime:

[*]Multiply that difference by 8 (the "number of inches per click", as you state).
Click to expand...
Asa looks like we have one thing in common. we both seen to be slightly dyslexic. i said 8 clicks per inch not 8 inches per click.
PM i sent to Asa
"scope test
ok Asa i took that scope out and tried it but hard to tell since it is on my 22 rimfire i have it sighted for 25 yards for hunting and i backed up to 50 yards for the test. shot a group (8 on first group and 10 shots on second group) then adjusted what should be 20 inches or moa at 100 yards and shot a group. correct me if i am wrong here but that should have changed poi by about 10 inches at 50 yards.
group moved by 5 inches center to center with a max of 7 inches and min of 3 inches, granted not benchrest standards but i can send you a pic if you want it. i think it proved my original point if by nothing else the scope didn't adjust like it should have. which i was not trying to get in a pissing match with everyone in the forum and looking back should have sent a pm to start with. notice my original point was you can't say it will adjust in moa without knowing what scope it is. after my post the scope was added which gives a basis for how it will adjust according to how other scopes of same make and model have adjusted. this one of mine is a cheap and old (maybe as much as 25 years old) bushnell.3x9 but it serves it's purpose while squirrel hunting.

as far as the moa-inch deal other than whoops i didn't cut the line and i dropped a point what is 1/2 inch at 1000 yards? 10 inches verses 10.47 again correct me there if i am wrong with moa being 1.047 inches.

may your benchrest groups all look like you cheated and your backers prove otherwise."

Boyd said it correctly and i said it screwed up. the scope may not adjust like it is supposed to. i apologize for any miss understanding and will now go back to my little corner.
 
Absolute misinformation about ALL scopes being in MOA...
Most Leupolds, and many others are IPHY.
Of course, 1/4" per 100yds, might not actually adjust that way. It could be less or more, and has to be validated for entry into ballistic software(just like scope height).

This is significant because IPHY is the highest resolution of adjustment, and is not MOA at all.
 
Gentlemen:

In Asa's post above he mentioned "splash" or bullet impact. When sighting in a rifle at a distance that it is not sighted in for try this. Shoot at the target and note the bullet impact point. Now point the rifle at the original point of aim. Do not move the rifle. Now adjust windage and elevation to get about 3/4 of the way to the point of impact. If you adjust all the way to the point of impact you will usually over correct. Shoot at the target again and repeat the procedure. In a couple of shots you should be on the paper. Note the approximate distance you moved the elevation from your last known sight point. Keep a note book and make an entry. That way you can go back to where you came from.

I shoot 600 and 1000 yards. I use a Weaver T-36. I know that it is two full revolutions of the elevation knob from 600 to 1000 yards either up or down. I am usually back near point of aim in a couple of rounds. Keep it simple.

Jeffrey Tooker
 
Jeffreytooker said:
Now adjust windage and elevation to get about 3/4 of the way to the point of impact. If you adjust all the way to the point of impact you will usually over correct
Click to expand...

Whoa, Whoa, OH NO.....
Well, unless your scope is unreliable to a point that negates all common sense....

A scope's POA adjusted fully to POI is right where it ought to be [POA = POI]
 
scope adjustment

Hi, I'm new to this forum, Very good stuff ! Been shooting a long time have always did this the hard way. Still a little confused- - zero at 100yds? OR-- 300yds?
Thanks, John
 
John,

Nice name there.

I carry out the following sequence:

  • Zero my scope at 100 yards
  • Prove that it's square at that distance by shooting up a plumbed line I draw when I set up my target - I usually go up 5 MOA three times
  • Adjust the windage turrent to a zero mark
  • Get a good 300 yard elevation on my home range
  • Adjust the turrent to zero reading.
John
 
A little scope adjustment tip
Always finish your adjustment turning the knob in a clockwise direction. If the direction that you need to go requires a counter colckwise move, turn a few clicks (half a dozen) and then come back to your desired setting. I got this tip, many years ago, from the late Dick Thomas of Premier Reticles. The reason for doing it this way is that when you turn the knob counter clockwise, you are backing the adjustment screw out, and counting on a spring to make the erector tube follow. For various reasons, this may not work perfectly. This is also a good idea when adjusting an objective that works against a spring (finish turning the objective in, clockwise as viewed from the front).
 
Hi Boyd, Being a oldtime machinest, I call what you describe as backlash. Have always took the backlash out past the mark - in the oppossite direction on cheaper scopes. I find tht I don't have to, on my Nightforce.

Thanks, John
 
John,
What we are dealing with here is a little different than a machinist's backlash. The erector tube is only screw driven in one direction. It depends entirely on spring pressure as the screw is backed out, so you should only go past and back up when your net adjustment is in a counterclockwise direction, and always finish in a clockwise direction (assuming RH threads). If you go past and back up when that leaves you finishing counterclockwise, you are back to depending on the spring.
 
Hi Boyd, Yep, your right , I know this
Some things we do without thinking. Sory about that.
John
 
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