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Scope question #6994864
09/19/20 08:08 PM
09/19/20 08:08 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
M
Mike in A-town Offline OP
trapper
Mike in A-town  Offline OP
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Joined: Sep 2013
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Northeast Oklahoma
I mounted a 4-32x50 on my 308. Scope is second focal plane.

It's zeroed at 100 yards and my latest target is set at 700 yards... Ballistic math says 5.5 mils of drop at 700 yards. If I leave the magnification at the lowest setting I can hit the target with a decent amount of regularity. But if I bump up to full magnification then I am completely off the map.

Is there a formula to determine my elevation adjustment when using higher magnification?

I ran a little test to see if my assumptions were somewhat correct:

1 mil at 100 yds is 3.6" So I divided 100 by 20 and of course got 5 yds. 3.6" divided by 20 is .18"

So I set up a target at 5 yards with two lines .18" apart and checked it with the scope at 4 power. It measured 1 mil. Then when I increased the magnification to 32 it measured 8 mils... That made sense. So I assumed at full magnification that 1 mil equals 8 mils, right?

So if that math was correct then I would need to divide my 5.5 mils by 8 and get .675 mils... So I held as close as I could (between .5 to 1 mil) and was still off the map.

Was I completely wrong with the math?

My 300 Win Mag has a FFP scope on it and doesn't change when magnification is increased... Much easier to use but a little more expensive.

Any help or advice would be greatly appreciated.

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6994872
09/19/20 08:14 PM
09/19/20 08:14 PM
Joined: Dec 2006
Posts: 34,241
Minnesota
330-Trapper Offline
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330-Trapper  Offline
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Joined: Dec 2006
Posts: 34,241
Minnesota
I'm bad with math... good thing I get closer when I hunt.
Sorry no help.


NRA and NTA Life Member
www.BackroadsRevised@etsy.com




Re: Scope question [Re: Mike in A-town] #6994889
09/19/20 08:26 PM
09/19/20 08:26 PM
Joined: Oct 2015
Posts: 1,985
Fingerlakes New York
robert.d12 Offline
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robert.d12  Offline
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Fingerlakes New York
Yes, your reticle change as you change the magnification. Usually a reticle is designed for max magnification, but on a 32x scope it might not be. What brand and model is it? You should be able to google what magnification the reticle is set for


The beauty of the second amendment is it wont be needed until they try to take it. -Thomas Jefferson
Re: Scope question [Re: Mike in A-town] #6994910
09/19/20 08:47 PM
09/19/20 08:47 PM
Joined: Jan 2011
Posts: 2,932
Indiana
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keystone Offline
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Indiana
Are you using the hold over marks on your scope or adjusting the turrets? If your using the turrets to adjust the main crosshair there should be no deviation no matter what magnification. If your using holdover marks then you would need to shoot at the same magnification that you sighted the rifle in with at that particular distance.

Last edited by keystone; 09/19/20 08:52 PM.
Re: Scope question [Re: robert.d12] #6994917
09/19/20 08:51 PM
09/19/20 08:51 PM
Joined: Jan 2011
Posts: 2,932
Indiana
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keystone Offline
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Indiana
Originally Posted by robert.d12
Yes, your reticle change as you change the magnification. Usually a reticle is designed for max magnification, but on a 32x scope it might not be. What brand and model is it? You should be able to google what magnification the reticle is set for


On a SFP the reticle does not change, the target does. The reticle is placed behind the magnification lense so it never changes size.

Re: Scope question [Re: keystone] #6994922
09/19/20 08:53 PM
09/19/20 08:53 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
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Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Northeast Oklahoma
Originally Posted by keystone
Are you using the hold over marks on your scope or adjusting the turrets? If your using the turrets to adjust the main crosshair there should be no deviation no matter what magnification. If your using holdover marks then you would need to shoot at the same magnification that you sighted the rifle in with at that particular distance.


Holdover.

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6994930
09/19/20 08:59 PM
09/19/20 08:59 PM
Joined: Mar 2010
Posts: 2,715
MT
Boone Liane Offline
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Boone Liane  Offline
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MT
If you’re using the reticle marks as holdover points, you need to remember the subtensions change with magnification in a second focal plane scope.

Most reticles are calibrated for max power, but some are not.

A one mil mark on high power (or the calibrated magnification point), will be two mils at half that power.


Last edited by Boone Liane; 09/19/20 09:00 PM.
Re: Scope question [Re: Mike in A-town] #6994948
09/19/20 09:14 PM
09/19/20 09:14 PM
Joined: Dec 2009
Posts: 8,159
The Hill Country of Texas
Leftlane Offline
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Leftlane  Offline
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Posts: 8,159
The Hill Country of Texas
They have phone apps that will do all the math for you now.


"Our nation is witnessing a merciless campaign to wipe out our history, defame our heroes, erase our values, and indoctrinate our children."
D. Trump
Re: Scope question [Re: Mike in A-town] #6994951
09/19/20 09:22 PM
09/19/20 09:22 PM
Joined: Apr 2018
Posts: 105
Ozark Mtns, AR
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JD Hornet Offline
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JD Hornet  Offline
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Ozark Mtns, AR
What is the brand of scope and welcome to long range shooting it ain't simple do your home work.


Farm Hard
Re: Scope question [Re: Mike in A-town] #6994952
09/19/20 09:23 PM
09/19/20 09:23 PM
Joined: Jan 2011
Posts: 2,932
Indiana
K
keystone Offline
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keystone  Offline
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Indiana
Originally Posted by Mike in A-town
Originally Posted by keystone
Are you using the hold over marks on your scope or adjusting the turrets? If your using the turrets to adjust the main crosshair there should be no deviation no matter what magnification. If your using holdover marks then you would need to shoot at the same magnification that you sighted the rifle in with at that particular distance.


Holdover.

Mike


So you have to think about the target changing size as you increase and decrease the magnification, the reticle does not change size. When your sighting in for 700yds you have to use the exact holdover mark at the exact magnification that you will always use at that particular distance. The distance between your holdover marks stays the same since your reticle doesn’t change size but your target gets much larger at higher magnification.

Re: Scope question [Re: Leftlane] #6994986
09/19/20 09:46 PM
09/19/20 09:46 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
M
Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
Originally Posted by Leftlane
They have phone apps that will do all the math for you now.


Yep, I just used the free one at gundata. It already had a chart for the factory loads i was shooting. I dont know what barrel length they used and I don't have a chrony to know my MV but the chart stated 138" drop at 700 yards... So that translated to 5.5 mils. That's what I held at and was able to hit 5 out of 8 so it had to be pretty close.

The gun is an AR10 so I doubt I'll ever have ragged hole/cloverleaf accuracy, but I'll push it as far as I can.

And you never realize how lousy and inconsistent factory ammo is until you start reaching out there. Handloads are next, but that will mainly be for the 300WM. I just don't see a production AR platform grouping as well as a decent bolt gun.

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6994992
09/19/20 09:54 PM
09/19/20 09:54 PM
Joined: Dec 2009
Posts: 8,159
The Hill Country of Texas
Leftlane Offline
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Leftlane  Offline
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Joined: Dec 2009
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The Hill Country of Texas
I haven't downloaded it but a guy was at my buddies shop was showing us his app that calculated everything including your barrel length and a huge number of factory loads. I myself like walking it in but yeah- I am not much of an ammo conserver and never have been


"Our nation is witnessing a merciless campaign to wipe out our history, defame our heroes, erase our values, and indoctrinate our children."
D. Trump
Re: Scope question [Re: JD Hornet] #6994996
09/19/20 09:59 PM
09/19/20 09:59 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
M
Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Northeast Oklahoma
Originally Posted by JD Hornet
What is the brand of scope and welcome to long range shooting it ain't simple do your home work.


Sightmark Wraith. No real windage and elevation adjustments to be made with it... I can adjust my zero but that's about it. Pretty sure it's mainly for varmint/hogs... It's NV capable and has an IR emitter so I KNOW that's what it's for. But it's fun to play around and see what can be done.

And yes, the LR shooting bug seems to have bit me. But any serious attempts at it will be done with my bolt gun... which isn't a specialized LR rig either... But it's all I have right now.

I may have to save up and get a decent rig but I'll never shoot competitively... I just want to see how far I can reach out and ring gongs... To see if I can.

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Leftlane] #6995001
09/19/20 10:06 PM
09/19/20 10:06 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
M
Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
Originally Posted by Leftlane
I haven't downloaded it but a guy was at my buddies shop was showing us his app that calculated everything including your barrel length and a huge number of factory loads. I myself like walking it in but yeah- I am not much of an ammo conserver and never have been


Oh yeah, there's a million of em.

I'll completely geek out over ballistics... My wife has threatened to smother me in my sleep if I keep discussing it. Lol

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6995012
09/19/20 10:18 PM
09/19/20 10:18 PM
Joined: Dec 2006
Posts: 3,235
Lower Alabama (Daleville)
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LAtrapper Offline
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LAtrapper  Offline
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Lower Alabama (Daleville)
A link to this article was suggested in a similar discussion recently- https://www.americanhunter.org/articles/2017/7/10/first-focal-plane-or-second-focal-plane/


Note to self- Engage brain before opening mouth (or hitting the ENTER key/SUBMIT button).

Ron Fry

Re: Scope question [Re: keystone] #6995015
09/19/20 10:21 PM
09/19/20 10:21 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
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Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Northeast Oklahoma
Originally Posted by keystone
So you have to think about the target changing size as you increase and decrease the magnification, the reticle does not change size. When your sighting in for 700yds you have to use the exact holdover mark at the exact magnification that you will always use at that particular distance. The distance between your holdover marks stays the same since your reticle doesn’t change size but your target gets much larger at higher magnification.




I think I understand what you're saying. Here's what I'm trying to wrap my head around...

When I zoom from 4x to 32x my target gets 8 times bigger. This was evidenced by my little 5 yard experiment.

Now if I'm at 700 yards and using 4x power and hitting with 5.5 mils of holdover and I zoom to 32x my target is now 8x bigger than it was at 4x. So is it correct to think that I would divide my 5.5 mil holdover by 8 to account for that? The math would seem to make that right but that's assuming it's proportional.

Or is it easier/more accurate to move back to 100 yards and rezero at 32x and go from there?

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: LAtrapper] #6995019
09/19/20 10:29 PM
09/19/20 10:29 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
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Mike in A-town Offline OP
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Mike in A-town  Offline OP
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Northeast Oklahoma
Originally Posted by LAtrapper
A link to this article was suggested in a similar discussion recently- https://www.americanhunter.org/articles/2017/7/10/first-focal-plane-or-second-focal-plane/


Yep, I read that a while back. No one ever offers a formula they just tell you that the math with SFP is complicated... And they're right.

I'm a huge proponent of FFP it's just a million times easier to compensate. SFP seems to be fine for about 300 yds and under because any change in magnification isn't going to shift your POI enough to matter at those ranges.

But I've got this ONE sfp scope. Lol

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6995025
09/19/20 10:35 PM
09/19/20 10:35 PM
Joined: Sep 2013
Posts: 7,223
Green County Wisconsin
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GREENCOUNTYPETE Offline
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Green County Wisconsin
what load are you using Mike?

in a second focal plane typically the only place the Mil dots or MOA depending on what it is at max magnification however some are not when you get above 12 power there is sometimes a mark for where the calibration point is.

is this the scope? https://www.foxoptic.com/product-review-sightmark-wraith-4-32x50-digital-day-night-scope/

is yours the digital scope?

if it is are you sure you are on the Mrad reticent as it looks to have 9 options with some mrad and some moa

for many of us it is easier to think in MOA than MRAD you may have options.

if you made a 10 centimeter square and placed it at 100 meters it should measure 1 mrad you may want to make a 55 centimeter square that should measure 5.5mrad at 100 meters to check calibration.


America only has one issue, we have a Responsibility crisis and everything else stems from it.
Re: Scope question [Re: GREENCOUNTYPETE] #6995032
09/19/20 10:49 PM
09/19/20 10:49 PM
Joined: Sep 2013
Posts: 8,125
Northeast Oklahoma
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Mike in A-town Offline OP
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Northeast Oklahoma
I'm getting ready to turn in Pete. I'll get back to you. Loads are Federal American Eagle 150 gr FMJ. No particular reason for using that load its just what I had the most of on hand.

Mike

Last edited by Mike in A-town; 09/19/20 11:01 PM. Reason: Added info

One man with a gun may control 100 others who have none.

Vladimir Lenin
Re: Scope question [Re: Mike in A-town] #6995035
09/19/20 10:59 PM
09/19/20 10:59 PM
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Northeast Oklahoma
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Mike in A-town Offline OP
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Yes Pete, that's it. And I am using the MRAD reticle with the dot in the center... I believe it's reticle #1 in the link you shared.

Mike


One man with a gun may control 100 others who have none.

Vladimir Lenin
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