Rifle Scopes SFP Question?
- Thread starter KeithR41
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Re: SFP Question?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KeithR41</div><div class="ubbcode-body">If my optics are regulated for a true MIL value at 15x. What is the value of a MIL at 3.5 and in between. I know there's a math formula for this but obviously I don't know it.
Thanks, 41 </div></div>
7.5x = .5 mil
3.5x = .23 mil
Formula: Current Magnification/Calibrated Magnification x mil
John
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KeithR41</div><div class="ubbcode-body">If my optics are regulated for a true MIL value at 15x. What is the value of a MIL at 3.5 and in between. I know there's a math formula for this but obviously I don't know it.
Thanks, 41 </div></div>
7.5x = .5 mil
3.5x = .23 mil
Formula: Current Magnification/Calibrated Magnification x mil
John
Re: SFP Question?
<span style="font-weight: bold">Wait</span>!, I'm so backwards in my head from using FFP's.
15x would be 1 mil
7.5x would be <span style="font-weight: bold"><span style="font-style: italic"><span style="text-decoration: underline">2</span></span></span> mil
Formula: Calibrated Magnification/Current Magnification x mil
This is why I use nothing but FFP! My head hurts now...
John
<span style="font-weight: bold">Wait</span>!, I'm so backwards in my head from using FFP's.
15x would be 1 mil
7.5x would be <span style="font-weight: bold"><span style="font-style: italic"><span style="text-decoration: underline">2</span></span></span> mil
Formula: Calibrated Magnification/Current Magnification x mil
This is why I use nothing but FFP! My head hurts now...
John
Re: SFP Question?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">This is why I use nothing but FFP! My head hurts now...</div></div>
I was just about to type an answer... classic example for the benefits of FFP I guess.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KeithR41</div><div class="ubbcode-body">So for example, 15/7.5 x 3.6?
That is 7.2. I' a little confused. What am I doing wrong?
41 </div></div>
Leave out the 3.6.
15/7.5=2, thats your subtension in mils. It's 2mils. 3.6 is probably stuck in your head because it's how many inches a mil subtends at 100 yards. Forget that, inches have no place whatsoever in this formula.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrob300</div><div class="ubbcode-body">This is why I use nothing but FFP! My head hurts now...</div></div>
I was just about to type an answer... classic example for the benefits of FFP I guess.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KeithR41</div><div class="ubbcode-body">So for example, 15/7.5 x 3.6?
That is 7.2. I' a little confused. What am I doing wrong?
41 </div></div>
Leave out the 3.6.
15/7.5=2, thats your subtension in mils. It's 2mils. 3.6 is probably stuck in your head because it's how many inches a mil subtends at 100 yards. Forget that, inches have no place whatsoever in this formula.
Re: SFP Question?
I find it easier to think in terms of the reticle mil mark distance relative to the object. When you decrease the mag from 15X to 7.5X, the object size is cut in half relative to the reticle, which doesn't change. So the distance between the mil marks at 7.5X is then 2.0 mil. At 5X, the object size is 1/3 that observed at 15X, so the mil mark distance is 3.0 mil. At 10X, it is 1.5 mil.
This is pretty easy with a 3.5-15X, because 15 is divisible by 2, 3, 5, etc. I'm waiting on a 5.5-22X, so I've been thinking about this. For my feeble brain, 22 is only easily divisible by 2 (11X), so I'll probably have to work up a cheat sheet or keep my pocket calculator handy.
I find it easier to think in terms of the reticle mil mark distance relative to the object. When you decrease the mag from 15X to 7.5X, the object size is cut in half relative to the reticle, which doesn't change. So the distance between the mil marks at 7.5X is then 2.0 mil. At 5X, the object size is 1/3 that observed at 15X, so the mil mark distance is 3.0 mil. At 10X, it is 1.5 mil.
This is pretty easy with a 3.5-15X, because 15 is divisible by 2, 3, 5, etc. I'm waiting on a 5.5-22X, so I've been thinking about this. For my feeble brain, 22 is only easily divisible by 2 (11X), so I'll probably have to work up a cheat sheet or keep my pocket calculator handy.
