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 Usage of Mil-Dot on variable-zoom scope
Molodoi  [Member]
7/30/2010 2:21:33 AM
Mil-dots on a scope can be used to estimate the distance and make corrections based on a pre-established ballistics table. Each dot corresponds to a number of minutes of angles.
But what if the scope has a variable zoom? Say a 3-9x40 scope. When one goes from 3x to 9x magnification, the MilDot reticle size doesn't change whereas the picture changes 3-fold, meaning all angle corrections vary as well, correct?
What's your opinion of MitDot variable zoom scopes? Practical? Should they be used at a fixed zoom?
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imortal  [Team Member]
7/30/2010 3:10:24 AM
This is true if the recticle is the the Second Focal Length (SFL). The recticle stays the same size and the zoom changes. Usually in that case, the mildot recticle is accurate at only a single magnification. If the recticle is in the First Focal Length (FFL), then the recticle changes size as you zoom your scope in and out. That means the mildot recticle is always accurate for ranging. However, in this case the recticle does change size, meaning it may be lost at low magnification, and at high magnification it may be too large for real precision work.
Molodoi  [Member]
7/30/2010 3:20:07 AM
Thanks for the info Imortal, that makes sense now.
Is there any way to know on which plane the reticle is located for these 2 scopes:
http://www.walmart.com/ip/CenterPoint-4-16x40mm-Scope/10248654
http://www.walmart.com/ip/Crosman-CenterPoint-3-9x40mm-Tactical-Hunting-and-Shooting-Scope/10248653
FALbert  [Team Member]
7/30/2010 3:20:48 AM
What you are describing is a second focal plane scope. The reticle is true MIL at one magnification which is specified by the manufacturer and this should be the one you would use for range estimation. Typically this is at the highest magnification.

If you get a first focal plane scope, which I prefer, the reticle is true MIL at every magnification as it too will vary. Combine the reticle with matching turret adjustments, IE MIL/MIL (not MIL/MOA), it will make your life much more easier.

I like variable scopes because I can see more or less of what I am aiming at when needed. Fixed power has its merits too. Usually cheaper cost, simpler, and less parts that can get compromised.

See this thread I posted at Sniper's Hide: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Main=125320&Number=1367861#Post1367861

Note that the Falcon is first focal plane (FFP) the Leupold is second focal plane (SFP). Both scopes are variable up to are 14X. The Leupold is true at 14X whereas the Falcon is GTG at all settings. Note the reticles are both identical in size at 14X. The drawback to the Leupold is the turrets are adjusted using MOA so you have to either calculate or use a MIL dot calculator. With the Falcon, if I see the point of impact is 10 MILs from the center, I just have to dial in 10 MILs to correct it. This would be true at any magnification. There are scopes with MOA reticles and MOA turrets such as those offered by Nightforce so you can go that route too.
SrBenelli  [Team Member]
7/30/2010 7:26:04 AM
One way to verify... get a large piece of white cardboard and draw a long, vertical line down the center. Then, very precisely draw a horizontal "hash" mark every 3.6".
Set it up exatly 100yds from your scoped rifle and observe the "pattern" you just drew as you zoom magnification in and out. When you find a power setting that exactly matches your "pattern", that's the setting you need to use to range your target via mil dots.
Dolomite_Supafly  [Team Member]
7/30/2010 7:41:35 AM
Originally Posted By Molodoi:
Thanks for the info Imortal, that makes sense now.
Is there any way to know on which plane the reticle is located for these 2 scopes:
http://www.walmart.com/ip/CenterPoint-4-16x40mm-Scope/10248654
http://www.walmart.com/ip/Crosman-CenterPoint-3-9x40mm-Tactical-Hunting-and-Shooting-Scope/10248653


Both are second focal plane. The mildots are only accurate at one setting for range estimation. I have the 4x-16x on a rimfire and use the mildot for holdover.

If you are using the mildot for hold over only then there is a way to use all the magnifcation on the scope. The correct setting on the 4x-16x above is 10x for estimating range. If you know the distance and using the mildot for holdover only at that point then you multiply the holdover by 1.6 to get the 16x holdover. Example, if the mildot holdover is 2 mils at 10x power then the same holdover is 3.2 at 16x power.

To find out what you need to multiply by on other scopes you take the highest magnification, say 9x and divide it by the ranging magnification, say 6x. This gives you 1.5. You would then multiply the 6x holdover by 1.5 to find the holdover for 9x.

Unfortunately there is no easy way to use the mildots for ranging at other powers or at least not as easy as when the scope is at the correct power. When the correct powder is used mildots are very easy to use. I can not imagine myself without a mildot now.

Dolomite
shrapmagnet  [Member]
7/30/2010 10:06:39 AM
Typically the highest setting is where mildots are accurate on 2nd FP scopes- however, on many of the cheaper scopes that are advertised as mildot, those dots are randomly spaced in the reticle evidently for the "coolness" factor, and in fact are not true mildots at all. I have seen this with many of the imported scopes that in appearance are meant to mimic tactical sniper scopes that are typically sold at gun shows for $200 or less.
kaneroy  [Team Member]
7/30/2010 10:47:45 AM
I must be a tard, cause my brain hurts reading this.
LoneWolfUSMC  [Member]
7/30/2010 11:28:22 AM
Originally Posted By Molodoi:
Thanks for the info Imortal, that makes sense now.
Is there any way to know on which plane the reticle is located for these 2 scopes:
http://www.walmart.com/ip/CenterPoint-4-16x40mm-Scope/10248654
http://www.walmart.com/ip/Crosman-CenterPoint-3-9x40mm-Tactical-Hunting-and-Shooting-Scope/10248653


IIRC both of those are SFP (accurate at only one power) scopes. However I would not bet on the reticle being accurate at any power. I have the 4-16x Center Point on a .22LR. It is NOT acceptable in my opinion. I thought it was pretty neat at first, but the plastic turrets have loosened up and it just dosen't have a quality feel to it at all.

If that is the class of scope you are looking at, the Vortex Crossfire 6-24x50mm 1" tube that SWFA sells for $99 would be a better option. I just put one on my 40XB. Although I have not finished any tracking tests (needed to get the 20MOA base on it) the glass is really nice for the price. It's still a SFP scope, but I am not going to be milling targets with the 40XB. I have LRF and if I want to do range estimation practice I will just bust out of of the .308's with a FFP scope that has been verified accurate.

If you can afford to spend more on an optic, get a First Focal Plane reticle. It will be accurate at all magnification ranges. If you ever get to the point that you are shooting tactical matches, the FFP will serve you well. You don't have to make sure you are set on the correct power for holds or leads. You just hold and shoot. You can then set the magnification at whatever you need to so that you can see what you need to see.
CLICKBANGBANG  [Team Member]
7/30/2010 1:30:15 PM
One of my scope is a veritable power Mil-Dot. I just have to remember to go to the highest power setting 16x.

Sightron SII 4-16x42 MD

Here.

The letter B is one mil. at max zoom, 16x.



Min Power
A 144
B 14
C 4.7
D 3.1
E .6

Max Power
A 36
B 3.6
C 1.2
D .79
E .1
LoneWolfUSMC  [Member]
7/30/2010 3:03:25 PM
Originally Posted By CLICKBANGBANG:
Min Power
A 144
B 14
C 4.7
D 3.1
E .6

Max Power
A 36
B 3.6
C 1.2
D .79
E .1


Having to convert Mils to inches negates the majority of the benefit of a Mil reticle and only works at known distances. If you don't know the distance, you won't know how many inches the reticle subtends.

Molodoi  [Member]
7/31/2010 1:14:58 AM
Originally Posted By LoneWolfUSMC:
Originally Posted By Molodoi:
Thanks for the info Imortal, that makes sense now.
Is there any way to know on which plane the reticle is located for these 2 scopes:
http://www.walmart.com/ip/CenterPoint-4-16x40mm-Scope/10248654
http://www.walmart.com/ip/Crosman-CenterPoint-3-9x40mm-Tactical-Hunting-and-Shooting-Scope/10248653


IIRC both of those are SFP (accurate at only one power) scopes. However I would not bet on the reticle being accurate at any power. I have the 4-16x Center Point on a .22LR. It is NOT acceptable in my opinion. I thought it was pretty neat at first, but the plastic turrets have loosened up and it just dosen't have a quality feel to it at all.

LoneWolfUSMC, good to know on the quality of these scopes.

CLICKBANGBANG  [Team Member]
7/31/2010 6:07:00 PM
Originally Posted By LoneWolfUSMC:
Originally Posted By CLICKBANGBANG:
Min Power
A 144
B 14
C 4.7
D 3.1
E .6

Max Power
A 36
B 3.6
C 1.2
D .79
E .1


Having to convert Mils to inches negates the majority of the benefit of a Mil reticle and only works at known distances. If you don't know the distance, you won't know how many inches the reticle subtends.



I'm sorry, I'm not following you. If 3.6 inches is one mil, then at 16 x, the dots are one mil. ? Thanks for looking at what I've got.
Dolomite_Supafly  [Team Member]
7/31/2010 6:54:44 PM
Originally Posted By CLICKBANGBANG:
Originally Posted By LoneWolfUSMC:
Originally Posted By CLICKBANGBANG:
Min Power
A 144
B 14
C 4.7
D 3.1
E .6

Max Power
A 36
B 3.6
C 1.2
D .79
E .1


Having to convert Mils to inches negates the majority of the benefit of a Mil reticle and only works at known distances. If you don't know the distance, you won't know how many inches the reticle subtends.



I'm sorry, I'm not following you. If 3.6 inches is one mil, then at 16 x, the dots are one mil. ? Thanks for looking at what I've got.


I think he is talking about using MILs for holdover then trying to dial it on your MOA knobs after you convert it. Or maybe he is just referring to mixing up the two.

I have a MIL/MOA scope and what I do is use a drop sheet that is in both MIL and 1/4 MOA for the distances I shoot at. I use the MIL scale for rough aiming ( I used to shoot a lot of steel) and if I want precise aiming I use the 1/4 MOA scale, dialing in the clicks I need on the turrets.

Hope this helps.

Dolomite
LoneWolfUSMC  [Member]
7/31/2010 8:50:52 PM
What I am getting at is a a second focal plane reticle adds a level of complexity to the formula. When you start engaging targets an varying ranges at varying magnification levels under time limits the problems become clear.

It's all well and good to say you can just set it and forget it but then where do you end up with you have to grab your rifle and run to the next firing point and your power selector ring bumps off your setting.

Of course if you shoot in a static position at static targets with all the time in the world, then it really doesn't matter. You can work around anything.

I still have SFP, MOA/Mil scopes. I have variable FFP scopes, and I have a fixed BDC/MOA/Mil scope.

The rifle I use for work wears a Variable, FFP, Mil/Mil scope. It follows the KISS principal.
CLICKBANGBANG  [Team Member]
7/31/2010 9:29:07 PM
Originally Posted By LoneWolfUSMC:
What I am getting at is a a second focal plane reticle adds a level of complexity to the formula. When you start engaging targets an varying ranges at varying magnification levels under time limits the problems become clear.

It's all well and good to say you can just set it and forget it but then where do you end up with you have to grab your rifle and run to the next firing point and your power selector ring bumps off your setting.

Of course if you shoot in a static position at static targets with all the time in the world, then it really doesn't matter. You can work around anything.

I still have SFP, MOA/Mil scopes. I have variable FFP scopes, and I have a fixed BDC/MOA/Mil scope.

The rifle I use for work wears a Variable, FFP, Mil/Mil scope. It follows the KISS principal.


I agree that it is a more complex system that is not needed. And I do agree this type of setup is far less that ideal for a battle gun. This scope is on a varmint gun after it sat on a deer rifle for 10 years. Most of the time now, I shoot paper and yotes with it. It's tons of fun to play with leading a moving yote at 350 yards. I've made that shot before, but missed many times too.
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