Rifle Scopes SFP Ranging w/reticle on different powers

fockell

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Has anyone had much experience using the reticle for holdovers and ranging at different power. I have NF 3.5-15 with the NP-R2 Reticle. I was considering using it on 7-1/2 power to create twice the MOA hold overs. I have no idea how repeatable it might be, just curius if anyone has explored this much..Thanks Brandon
 

fockell

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Re: SFP Ranging w/reticle on different powers

Thanks. I will experiment with this over the weekend. -brandon
 

B.Bates

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Re: SFP Ranging w/reticle on different powers

here is an old article i saved from accurate shooter

Verifying the True Value of Your Scope Clicks
Filed under: Optics — Tags: Elevation, MOA, Scope — Editor @ 3 amLet’s say you’ve purchased a new scope, and the spec-sheet indicates it is calibrated for quarter-MOA clicks. One MOA is 1.047″ inches at 100 yards, so you figure that’s how far your point of impact (POI) will move with four clicks. Well, unfortunately, you may be wrong. You can’t necessarily rely on what the manufacturer says. Production tolerances being what they are, you should test your scope to determine how much movement it actually delivers with each click of the turret. It may move a quarter-MOA, or maybe a quarter-inch, or maybe something else entirely. (Likewise scopes advertised as having 1/8-MOA clicks may deliver more or less than 1 actual MOA for 8 clicks.)
Reader Lindy explains how to check your clicks: “First, make sure the rifle is not loaded. Take a 40″ or longer carpenter’s ruler, and put a very visible mark (such as the center of an orange Shoot’N'C dot), at 37.7 inches. (On mine, I placed two dots side by side every 5 inches, so I could quickly count the dots.) Mount the ruler vertically (zero at top) exactly 100 yards away, carefully measured.
Place the rifle in a good hold on sandbags or other rest. With your hundred-yard zero on the rifle, using max magnification, carefully aim your center crosshairs at the top of the ruler (zero end-point). Have an assistant crank on 36 (indicated) MOA (i.e. 144 clicks), being careful not to move the rifle. (You really do need a helper, it’s very difficult to keep the rifle motionless if you crank the knobs yourself.) With each click, the reticle will move a bit down toward the bottom of the ruler. Note where the center crosshairs rest when your helper is done clicking. If the scope is accurately calibrated, it should be right at that 37.7 inch mark. If not, record where 144 clicks puts you on the ruler, to figure out what your actual click value is. (Repeat this several times as necessary, to get a “rock-solid”, repeatable value.) You now know, for that scope, how much each click actually moves the reticle at 100 yards–and, of course, that will scale proportionally at longer distances. This optical method is better than shooting, because you don’t have the uncertainly associated with determining a group center.
Using this method, I discovered that my Leupold 6.5-20X50 M1 has click values that are calibrated in what I called ‘Shooter’s MOA’, rather than true MOA. That is to say, 4 clicks moved POI 1.000″, rather than 1.047″ (true MOA). That’s about a 5% error.
I’ve tested bunches of scopes, and lots have click values which are significantly off what the manufacturer has advertised. You can’t rely on printed specifications–each scope is different. Until you check your particular scope, you can’t be sure how much it really moves with each click.
I’ve found the true click value varies not only by manufacturer, but by model and individual unit. My Leupold 3.5-10 M3LR was dead on. So was my U.S.O. SN-3 with an H25 reticle, but other SN-3s have been off, and so is my Leupold 6.5-20X50M1. So, check ‘em all, is my policy
 

Lindy

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Re: SFP Ranging w/reticle on different powers

What issue of that magazine was it in?

In any case, if you want to read <span style="font-style: italic">all</span> of what I wrote on that subject, here it is:

Optically Checking Rifle Scopes

That article includes the method for calibrating an SFP scope for use at half power.
 

fockell

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Re: SFP Ranging w/reticle on different powers

Lindy- Great article! I was sure I wasn't on to anything new, however I found this very interesting. I can only imagine how useful this will be. Once I follow your direction I am going to create a seperate range card for 7-1/2 power. Thanks Brandon
 

Lindy

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Re: SFP Ranging w/reticle on different powers

Thanks! I'm glad you found it useful.
laugh.gif
 

Grump

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Re: SFP Ranging w/reticle on different powers

A SFP scope can also do a passable job of ranging using the power settings, so long as you bench-test to *know* what magnifications mean compared to the markings, *and* you really know the size of your target.

I suspect that if someone put as much time and thought into it as we do learning mil-dot ranging, it could be at least as accurate as any optical ranging method. The biggest disadvantage over mil ranging, of course, is that you are limited to the power-span of your magnification--typically 3:1, 4:1, or 5:1 for most variables. Those pricy 10:1 zooms don't appear to be very well proven yet.