Rifle Scopes Calculating Correct Mil Value In a Second Focal Plane Scope

[TiEnv700]

I am looking to get a scope to start long range shooting/practical precision shooting. I understand the major difference between FFP and SFF with regards to the accuracy of the reticle values at varying magnification settings. The scopes in FFP tend to cost a pretty penny so I am leaning toward a SFF.

When using a SFF scope, if the mil values are calibrated for say 10X and you change to 14X magnification, how do you calculate the new mil values for the reticle measurement marks?

 

[MoBoost]

It is possible and quite simple, but just DON'T DO IT.
Set the zoom to "1:1" Mil-Dot, learn how to use it proficiently.

 

[roggom]

You have to refer to the manufactures literature for sub-tension values and do some cross multiplication. As stated, keep it 1:1 and dont get hung up on the math.

Dial for elevation, hold for wind and get lots of time behind the trigger.

 

[mnr]

For my Sightron SIII 6-24x50 the reticle is calibrated for 1 mil spacing at 24x magnification. To keep the math easy I typically only either use it at 6x, 12x, and 24x if I am trying to range something/do a reticle holdover/self correct based on splash. 1 mil at 24x, 2 mils at 12x, 4 mils at 6x.

 

[jjrgr21]

most scopes are calibrated for high mag

 

[427Cobra]

Buy a fixed power 10x Super Sniper with MRAD knobs, use it, and abuse it while saving up for a FFP scope.

 

[runningun6mm]

Another option - have scope set to mil 1-1 magnification when "milling" a target. Use whatever power setting you wish when using rangefinder. I started with a sfp scope and it was extra math to do anything but leave it on the specific power setting for which the mils were correct.

 

[redneckbmxer24]

Do you really think saving a little bit of money is worth the bullshit of figuring out values, keeping the data, and doing a bunch of extra math?

With as many FFP scopes as there now are on the market you can find something in every price range. The SWFA 3-15 is $700 and the Bushnells start just a little more than that. I'm not sure what SFP scope you're going to get that's halfway decent for less than that.

 

[waveslayer]

Or just use a calculator

Sent from my SCH-I545 using Tapatalk

 

[Thorncreek]

For my Sightron SIII 6-24x50 the reticle is calibrated for 1 mil spacing at 24x magnification. To keep the math easy I typically only either use it at 6x, 12x, and 24x if I am trying to range something/do a reticle holdover/self correct based on splash. 1 mil at 24x, 2 mils at 12x, 4 mils at 6x.

+1

 

[TiEnv700]

Thanks for the replies I figured it would be more trouble that it's worth in savings. I am leaning towards the SWFA 3-15x42 do any of you have experience with the SWFA line?

 

[remr5]

buy a copy of magpuls precision rifle series. It will shed some light on this topic and is a great deal of knowledge

 

[dAyLiTe]

Glad you've switched to FFP... you were heading into a world of pain....
I've got a MTC/Optisan Viper 4-16 that has the worst of all worlds... nice Mil reticle, MOA turrets and SFP.
...I bought it before I knew anything, and have hated it ever since because of the amount of crap I have to figure out at any distance.
I don't even want to sell it as I'm not sure if I really want to put that amount of pain on someone else.

 

[sib1948]

Buy a fixed power 10x Super Sniper with MRAD knobs, use it, and abuse it while saving up for a FFP scope.

This would be you cheapest and best option for what you're wanting. 10X will get you to 500 yards and the Super Sniper scopes are rugged and have good glass. You will learn quickly, this is not a cheap sport. The best way to improve is just use whatever you have and get out and start shooting-even a 22LR or 223 in bolt action.

 

[Notso]

To the OP, if you're still really set on an SFP scope, the Vortex manual does a nice job of explaining how the different magnifications work. Here:

http://www.vortexoptics.com/uploads/web_manual_ret_viper-pst-6-24x50-sfp_r624s1-m-12a.pdf

The other thing to consider that I don't think anyone has said yet is if you DO get an SFP scope - you need to go to the range and actually determine where the scope is correct for the 1:1 subtension. Just because the manual says that the correct setting is 16x or 24x or whatever, the magnification ring on the scope may not be exactly right when you have it set to that spot. You basically have to play with the scope by looking at a scale at some range (usually a ruler) and play with the magnification ring until it is exactly matching the reticle. Then take a marker and mark that spot on the scope. It gets fun if that mark is at something like 16.5x or 17x instead of the listed number. Because then using the 1/2, 1/3, 1/4 trick is going to take even MORE brain power to do math.

Really, just get an FFP and make your life easy. But as long as you understand what you're getting into and what's involved to be accurate, the SFP will work fine.

 

[TiEnv700]

Thanks for the help. I am pretty dead set on the SWFA 3-15 it seems to be the best bang for the buck only lacking a zero stop and illumination, but I did see the zero stop shim kit one of the members on here sells. I found (and put on law away) a Remington 700 at my local gun shop built by their gunsmith, it is a 308 28" stainless barrel with 11 degree crown, action has been trued/printed, and it's glass bedded in a B&C fully adjustable medalist varmint tactical stock. Once I get the lay away ticket paid I will start saving for the optic. Thanks again for the help.

 

[Notso]

Zero stop kits would be WAY down on my list of things to buy if you're just getting into a new rifle.

 

[TiEnv700]

The zero stops are down the list for sure. A DM bottom metal is at the top, along with bipod, then probably threading for a brake, but a lot will be put into ammo and trigger time before I even reach that point.