Question about SFP scope values.

[GoatPilot87]

Hey guys, I have a question about second focal plane scopes. I have a Sightron SIII 6x24 LRMD/CM scope on my Savage. This was the first mil/mil scope I've ever used or purchased. I've read tons about mils, equations, ballistic calculators, etc and watched and read a lot Frank has put up, and from multiple other sources, so I have used the search bar, and Google as well. Now that were in a new house with some land, my daughters finally starting to get outta diapers, and I work a better shift I'm trying to shoot further. I do have one question I couldn't find an answer to, or if I did it didn't hit me when I read it. I was impatient and bought this scope knowing Sightron had a good rep, and I couldn't swing a Night force (rifle, optic, and accessories were bought the night we checked in to the hospital to have our daughter) and didn't at the time understand sfp vs ffp optics...now I do. I plan to get a ffp Night force or some other in the future but for now,I have what I have. Ok, to the question, I understand my mildot reticle is only true at 24x (max), and a mil at 100yds is 3.6", I also understand that everybody experienced says FORGET using measurements like inches, but for the sake of my lame understanding, just bare with me. So, if I'm a mil to the left at 100yds at 24x, I have .1mil clicks, it's 10 clicks right to adjust. My question is what if I'm set on half, or 12x? I know by my manual at half power the reticle values are doubled, i.e. 7.2" per mil. So the confusion is that when power is lessened and things are doubled, does the .1mrad value also double to .2mrads per click, and would it still require only 10 clicks right? I know I'm gonna get chewed out, laughed, and flamed as much as this is explained everywhere but in all honesty I don't have a bunch of guys locally that I know to ask for help. I will be signing up for some sort of long range classes near the northern Alabama area when I find one that's feasible. Anyways, thanks guys, it'll just be nice to get back into my hobby since I have time again. God bless.

 

[Shivy85]

Your click values will always move the reticle 0.10 mil, regardless of magnification level. The miliradian "ruler" on you reticle will be out of proportion you zoom out.

 

[bogeybrown]

Yep, what he said. I still keep a SFP mil/moa Mk4 for sentimentality and to remind myself why I'll never do that shit again. Try doing that calculation and then converting your mil correction to MOA adjustment.

As as for being flamed and so forth, I think you'll find (at least on the new kinder gentler Hide) that if you ask a legit question in the manner that you did you'll get the best answer we can offer. Sure, they may be a little wise-assery, but a huge number of the true asshats didn't make the multiple moves between forums and we appear to be enjoying a respite from shitting on each other all day.

 

[GoatPilot87]

Thanks guys, I knew I was over complicating it. So to add to my question, use the same scenario above. I'm at 100yds, impact is 1mil left, I'm on 12x (again, a mil will be 7.2" at 100yds, I know...forget other measurements), so at 12x is it still 10 clicks right? I understand most all that I've read about mils, and I know the SFP part is what is screwing me up, but as I said, live and learn. For some damn reason I'm having trouble understanding what I need to do if I'm not staying on max magnification and work up whatever formulas I'll need until I get a FFP scope because my goal is to start trying PRS. Thanks for the help so far gentlemen, I tried to post that confusing ass question as astutely as possible so everyone would know I was being sincere lol. I'm only 29, so I've got plenty of time to screw up and learn from them.

 

[bogeybrown]

I promise I'm not being an asshole when I say that if you want to dial corrections from observed splash/impact then you're going to go nuts in SFP unless you're reliably shooting from whatever power gives you "true" mils in your optic. Time is likely to kill you in a PRS stage.

You can shoot a follow follow up in a SFP based solely on observed impact and a correction in your reticle but I wouldn't recommend trying to dial that correction unless you're on max power. So if you're on 18X and shoot, miss what appears to be .3 right through the scope, then just come left .3 left through the scope on your reticle. Use your reticle as a ruler and hold off based on your miss.

Assuming your turrets track properly, your turrets will always dial in true mils even though you're not always seeing true mils in your reticle (on less than full power). Assuming your scope is at true mils at 24 power, you can never be certain that you're at "true" half power when you dial to 12. You may be a fraction off to one side or another that's going to blow your conversion,

short story long: use your reticle as a ruler, but don't try to dial corrections unless you're on whatever power guarantees that you're on true mils, just shoot a hold-off based on what you see in the reticle.

 

[bogeybrown]

Realized I missed a part of your question: yes, regardless of what power you're on, if you're actually a mil left at 100 then you dial 10 clicks correction. if you walked down range and measured your miss at 3.6" then it takes 10 clicks to adjust, regardless of what that mentally looks like through your SFP reticle on another power.

 

[Gunfighter14e2]

Try Whitefeather as your very close to it, know a few guys who went there an to them it was great.
https://www.whitefeather.biz/faq/
There is nothing wrong with a SFP scope. Many of us bought into the FFP rage, but most have reverted back to SFP do to shooting subs long w/o knob'ing. Plus with some of the new X-mas trees that Leupold offers they are just as fast holding as anything else out there. Nice to have 85-90 moa plus(depending scope) on low power for subs or 64 at half, 32 high, with 40/32/16 moa of wind holds.

 

[bogeybrown]

One thing I failed to mention: you can still create dope cards or use a solver and dial your DOPE for any range without any issues. The mechanical adjustment of scope will always be in true mils. So for PRS you can have your dope card and be fine, just plan to shoot hold-offs at any power other than full. Which is pretty much what appears most people do anyway: dial for distance and shoot a hold off for correction if necessary. Holding off for wind would best be done at full power however.

 

[SubOptimal]

I have two very different scopes on my "good" rifles. When I bought my 6.5CM rifle, I was flush with cash and put on a Bushnell H2DMR scope, FFP, mil/mil turrets and reticle. Simple to zero as I could dial my adjustments for zero in. At the time, I was using a Ruger Gunsite Scout rifle in 308 as a hunter and had mounted a Swarovski Z5 with MOA turrets and a BDC reticle. Following the directions in the manual, I did all my adjustments at 1/2 power or 9x on the 18x scope. I switched that scope to my 6.5x47 Lapua and managed to get myself wrapped around my axle trying to zero that gun. Then I remembered that the reticle was BDC, NOT moa. Problem solved and I played with JBM to develop a card for the scope and gun. Whole different data book but the gun basically stays at the 100 yard zero and I hold everything. I suppose I could go back to Swarovski and have a different reticle fitted but I have good data now, at least out to 500 and don't really need any more.

 

[PlinkIt]

I think you are adding an extra step thinking of inches still...

As they explained before the turrets are always true

Just try thinking of the magnification values like this...

At 24x every mil dot is 1 mil
At 12x every mil dot is 2 mils
At 8x every mil dot is 3 mils
At 6x every mil dot is 4 mils

Just pick the magnification that works best for your given conditions and adjust turrets according to that scale

 

[C_R_Slacker]

I shoot a sfp nightforce and I've had the same questions. I had to draw it out to understand it, so don't feel bad. The guys above are correct, but wouldn't it be four mils at 6x, Plinkit? From 12x to 6x is reducing by half, so shouldn't the mil value double from 2 to 4?

Anyway, to help you make sense of it, buy, print, or make a mil based tall target and get out and look at it through your scope on different magnification settings. Seeing it first hand will help you understand what is going on.

 

[PlinkIt]

...but wouldn't it be four mils at 6x, Plinkit? From 12x to 6x is reducing by half, so shouldn't the mil value double from 2 to 4?...

good catch, I think you might be right. It's been so long since I've done SFP now it's not something I try to keep up with anymore.

24÷12=2
24÷8=3
24÷6=4

not sure what I was thinking the other night

On another note
Set up a reference target at a known distance
3.6" at 100 yards
Mark the magnification ring when the values are correct at 2x,3x,4x.... Etc
As the magnification rings may not be perfectly labeled either. Not to mention it's much easier to line up a perfectly scratched line than guess when the 12 is exactly in line with the reference dot.

 

[domdoc]

Do not throw your SFP scope away. You can do things with it that cannot be done with a FFP scope. For instance, let's say your scope mount doesn't have any cant for long range, and your $2,000 Nightforce won't bring your POI up to the target level at 1,000 yards. With SFP, you can dial the magnification down from 24 to 12, and use your mildots to get a precise holdover, even after you run out of vertical adjustment on the scope turret. I'm an unrepentant "inches" guy, because my holdoff on hunting and F-class shooting is in inches, measured by Mk II eyeball through the scope. Let's say your bullet impacts real low at 1,000 yds. with the scope turret as high as it will go. You shoot again, using the 5th mildot down, which is all you've got. Now you see impact 6 ft. low. Then you wind the magnification down to 12x, Now each of those mildots gets 72" of elevation instead of 36". So halfway down the reticle (2.5 mildots) gets you to where you were (impact 72" low), and you need one more mildot to come up 72" more, and you settle in at 3.5 mildots toward the bottom of the reticle. Bang. 12-power is plenty to survive at an F-class match, especially if 24-power can't put you on the target.

 

[Shifty6BR]

Do not throw your SFP scope away. You can do things with it that cannot be done with a FFP scope. For instance, let's say your scope mount doesn't have any cant for long range, and your $2,000 Nightforce won't bring your POI up to the target level at 1,000 yards. With SFP, you can dial the magnification down from 24 to 12, and use your mildots to get a precise holdover, even after you run out of vertical adjustment on the scope turret. I'm an unrepentant "inches" guy, because my holdoff on hunting and F-class shooting is in inches, measured by Mk II eyeball through the scope. Let's say your bullet impacts real low at 1,000 yds. with the scope turret as high as it will go. You shoot again, using the 5th mildot down, which is all you've got. Now you see impact 6 ft. low. Then you wind the magnification down to 12x, Now each of those mildots gets 72" of elevation instead of 36". So halfway down the reticle (2.5 mildots) gets you to where you were (impact 72" low), and you need one more mildot to come up 72" more, and you settle in at 3.5 mildots toward the bottom of the reticle. Bang. 12-power is plenty to survive at an F-class match, especially if 24-power can't put you on the target.

Right on, right on ....on a smaller scale, I have a vortex hs-t mrad sfp on my precsion .22 with subtension values at 16x. Shooting 400yds with cci sv I need 21 mils, turrets are maxed out at 16 so making things easier on myself I half my magnification at 8x and give myself a hold of 2.5 mils, this method really helps if I am holding for wind as well at those longer distances. Vortex has made things a little easier by only marking the values of importance on the magnification ring. YMMV