Rifle Scopes How do you use the reticle subtensions in a SPF variable scope for hunting ?

[mtmander]

I have looked thru many posts on several forums and did not find how you would use the reticle subtensions (SPF scope)

for hunting. I know you can dial or hold over but that is all I found. I know you can even use a formula , magnification in half doubles the value between the subtensions, etc......., but I did not find any posts that used that for hunting. Generally the posts said a SPF is better than a FFP for hunting because the reticle stays the same size for any magnification or it may be better in low light but nothing about use of the subtensions.

So I would like to know how you use the subtensions for hunting, thanks

 

[RFtinkerer]

I disagree SFP is better for hunting purely because I like to use lower magnification than the max. The Vortex PST series does show the reticle magnification effect at different zoom settings with detents in the zoom set. As long as you keep that in mind, it works. But I actually like FFP better just because hold-offs work correctly at any magnification. Easier and keeps my focus on the job. SFP is useful for the smaller reticle at max than FFP ends up with.

 

[bodywerks]

You mean SFP.
Nearly all sfp scopes subtend 1:1 at their max zoom. From there you have to start doing math. Half zoom means you have to double what you're seeing. If at half zoom the target subtends 2 MOA it is actually 4 MOA, etc.

Sent from my DROID BIONIC using Tapatalk 2

 

[Clark]

Do you mean "SFP"? for second focal plane.
SPF is sun protection factor for rubbing on little kid's faces.

I have "FFP" IOR 2x10x42 that I got used here on SH, and it is a nice scope, but useless for hunting. The MP-8 reticle all but disappears with a dark green back ground.

I have been using SFP 2x7x32 Leupold scopes with the addition of an aftermarket Stoney Point turret. These are not on the Stoney Point website and were soon out of stock everywhere when Stoney Point got bought out, but they are showing up again, so someone is manufacturing them:
Stoney Point Target Knob Leupold Scopes (One Only).

Then I strap a piece of cardboard to the rangefinder with a rubber band.
I get the info from Quickload program.
It says something like
260 Rem 120 gr Ballistic tip
Range___ elevation___ 10mph cross wind
200 yards ___ 0 moa ___ 1.5 moa
300 yards ___ 2 moa ___ 2.3 moa
400 yards ___ 4.6 moa ___ 3.3 moa
450 yards ___ 6 moa ___ 3.8 moa
500 yards ___ 7.5 moa ___ 4.3 moa
550 yards___ 9.25 moa ___ 4.8 moa
600 yards ___ 11.1 moa ___ 6.0 moa

It does not matter if the scope is on 2X or 7X.
A 400 yard shot is 100% sure thing.
A 600 yard shot is 50% probability of a clean hit.
So just keep stalking until the range finder says 400 yards.

 

[Chiller]

if you want to do all the math and map the glass out, why not just get the FFP?

if you have a SFP glass, great....Map the reticle and drive on. I like the idea of FFP from a KISS principle.

 

[hlee]

This is how I use them. Well, this is how I use the duplex reticle, which works out the same. I know that at 9x, and at 100 yards the fine portion of the reticle (Leupold 3-9x40 Vari-XII) subtends 3 inches. Given that information, and given that I can find something of known size at the target distance, I can estimate the range to target. For example, if the chest of a whitetail deer is 18" deep and it evenly fits within the fine portion of the reticle then I know that deer is 600 yards away (18" / 3" per 100 yards). Except for very low light I do not change the magnification from 9x.

All SFP scopes have a magnification where the subtension dots (lines) are correct (1:1 as referenced above). This magnification may or may not be the max for the scope. However, this "ranging magnification" should be highlighted on the adjustment ring. If it is not, I would make a substantial effort to determine the correct magnification for the reticle, then I would mark that magnification power permanently on the adjustment ring.

 

[waste_knot]

Not sure what you are asking. Do you mean how do I measure range (distance to target) with a reticle and whats the difference with FFP SFP.

 

[mtmander]

Yes I did mean "SFP" for second focal plane

I am trying to decide on how I would use the subtends on a SFP scope for hunting. I don't see a value for the subtends during hunting and I
want to see how others used them or did not use them.

 

[One-Eyed Jack]

I hunt using holdovers - knowing the distance to the target, I've already determined how much elevation and windage I need. Then I use the subtensions marked on the reticle to measure these holdovers for aiming. With a FFP reticle, I simply hold using the values on the reticle. With a SFP reticle, the values depend on magnification. At full magnification the reticle subtensions are the reticle values. At half-full magnification, I hold half the subtensions I need; at a third-full magnification, I hold one-third of the subtensions I need in elevation and windage. If you don't use the reticle for holdovers and simply dial in your elevation and windage, then you will use the cross hairs, for example, to aim. However, you might want to correct your aimpoint if you miss a shot, and using the reticle subtensions can be useful.

 

[roggom]

OP let us know which scope and retical you have. Then some suggestions can be made. For example, I have a leupold VX3 with a duplex, it is designed to bracket a deer (18") in the thin portion of the retical and as you adjust the mag, the mag numbers correspond to given yards.

I also have a NF compact with mildot, I can used the mildot at max (x10) and make readings, or drops. I have also worked out a similar way of bracketing that subtends 150Y at x2.5 and 500Y at 10 with 1 mil.


Vortex and Nikon both have programs that will do all the math for you as well.

 

[Dkindels]

The use in hunting of any sub tensions would be useful if you knew the approximate size of the animal you are hunting. If you know this, you can do some calculations ahead of time to get how many MOA or MIL that measurement equals at various yardages. Using the SFP reticle you would be able to estimate range at the magnification where subtensions equal 1 MOA or MIL. The manufacturer will generally tell you what mag this is. For example, if your target is 10" (approximately back to chest on coyote) you look through the scope and see that the coyote covers 3 MOA. That would equal about 320 yards. If you know how many MOA your bullet drops, you simply hold over that many MOA subtensions on the reticle and fire. Hope that makes sense. You can find calculators on the Internet to help with calculating distance based on size of target.