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How Magnification Affects a Bullet-Drop Compensating Scope

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April 29, 2012
How Magnification Affects a Bullet-Drop Compensating Scope - 3

A few months ago, a reader sent in this question:

For Christmas I got a scope with a bullet-drop compensating reticle, but if I understand the directions, I have to shoot on the highest power to get the crosshairs to work. I like to keep the magnification at 6X. Will the secondary crosshairs work at that power?

Here's my answer...

Riflescopes with multiple aiming points for distant targets are all the rage. In fact, it’s hard to find a scope with a simple duplex crosshair these days, as the optics industry focuses on BDC (bullet-drop compensating) reticles that are designed to end the old how-high-over-his-back-should-I-hold question that confronts hunters making long shots.

The best BDC reticles are engineered to conform to a ballistic curve, the arc of a bullet as gravity pulls it earthward. The worst are random aiming points that have more to do with marketing than ballistics.

In order for the ballistic curve to match the scope’s aiming points, you must start with a known zero. Most manufacturers recommend a 100-yard zero with standard calibers and a 200-yard zero with flat-shooting magnums. The secondary aiming points should be close to 100-yard increments, as long as the scope is on its highest power.

Here’s why power matters: Because BDC reticles are almost always in the scope’s second focal plane, the size of the crosshairs doesn’t appear to change as you change magnification. But what does change as you ramp up the power are the lower references below the center crosshair. These hatches appear to move up the target as magnification increases and down the target as it decreases.

The good news is that both your zero and your power settings are infinitely adjustable. Spend time at the range tuning the reticle to your pet load and favorite magnification. Or use an online ballistic calculator (like Nikon’s Spot On) to marry your aiming points with your load and the scope’s magnification.

Comments (3)

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from BurrisHunt wrote 29 weeks 6 days ago

Different reticles, different brands, slightly different behaviour. You gotta get used to your scope. I'm not a fan of the Nikon Spot On app (seems very innacurate to me?) I cut my BDC teeth on this optic www.bestriflescopereview.net/nikon-p-223-3x32-matte-bdc-carbine-riflesco...
Took a while for me to get used to BDC but when you get the hang of it you fall in love with it. www.bestriflescopereview.net

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from 6phunter wrote 2 years 20 weeks ago

informative insight,thanks ANDREW

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from horsethief wrote 2 years 20 weeks ago

The Redfield AccuRange 3-9x-40mm bullet drop compensating reticle was designed to work at the 9x setting. I tested the scope on my 300 Wby Mag at 7-8-9x settings and found 9x is the most accurate of the three. Since the size of the reticle does not change with the magnification (on my scope), you can see the hold-over points on the target better at 9x than you can at 7x. For the loads I shoot, the hold-over points are right on with a 200 yard zero.

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from horsethief wrote 2 years 20 weeks ago

The Redfield AccuRange 3-9x-40mm bullet drop compensating reticle was designed to work at the 9x setting. I tested the scope on my 300 Wby Mag at 7-8-9x settings and found 9x is the most accurate of the three. Since the size of the reticle does not change with the magnification (on my scope), you can see the hold-over points on the target better at 9x than you can at 7x. For the loads I shoot, the hold-over points are right on with a 200 yard zero.

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from 6phunter wrote 2 years 20 weeks ago

informative insight,thanks ANDREW

+1 Good Comment? | | Report
from BurrisHunt wrote 29 weeks 6 days ago

Different reticles, different brands, slightly different behaviour. You gotta get used to your scope. I'm not a fan of the Nikon Spot On app (seems very innacurate to me?) I cut my BDC teeth on this optic www.bestriflescopereview.net/nikon-p-223-3x32-matte-bdc-carbine-riflesco...
Took a while for me to get used to BDC but when you get the hang of it you fall in love with it. www.bestriflescopereview.net

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