Can anyone explain how zoom affects the CDS dial.

[Jchiggins2012]

I am wanting to buy the CDS system. Just wondering how the zoom is factored in. Do you zero it at the Max zoom, then use a windplex or bdc for adjustments say if you set it for 300 yard then increase or descrease the zoom?

Just confused. Did a search, not too much on the CDS and Zoom questions.

Thanks,
Joel

 

[VikingsGuy]

Vertical CDS dialing and BCD are two different ways to accommodate shots longer than the original zero due to bullet drop. CDS dialing resets your cross-hairs so that your actual POI at the desired range is at the center of your cross-hairs despite previous zero - this is not effected by zoom. In contrast BDC markings let you more readily and consistently "hold over" to compensate for a distances longer than original zero - in first focal plane scopes hold over "value" is not effected by zoom, in second focal plane scopes BCD hold over "values" are dramatically effected by zoom. Essentially same for windage horizontal adjustments, but basis no wind vs current wind instead of distance from original zero.

For vertical, I would use one or the other but not both. Same for horizontal. But these are independent choices. For example, I may dial for vertical and use windplex to adjust windage point of aim rather than dialing.

 

[Tjay]

What was said above...

My understanding is.

CDS is not affected by scope power changes you dial your range and shoot on whatever power you want.

BDC systems are only accurate on the power specified by the maker. You can make your own chart for different power settings.

 

[Curvebow]

I agree with the above posts....

 

[ntodwild]

The CDS system is custom to Leupold and is based on the exact bullet/cartridge you are shooting. Given, elevation, caliber, muzzle velocity, ballistics/drop at 2,3,4,5,6 yards, elevation of scope mounted above the rifle. Leupold builds a "Custom Dial System" based on those particulars for your rifle/caliber. Soooo It does require some work on your part to have one built. Leupold needs all those parameters. The CDS leaves no questions. If you range an animal at 400 yards, set your scopes elevation dial at 400 yards (4 on the dial) and the cross hairs will match the ballistics of the specified caliber/rifle for which the dial was built for.

Depending on your thought process, this is either a great system or not.

Cons: If you decide to go to another bullet weight or different load, well,.....throw that CDS dial out the window and order another for the new cartridge. The other down side is that it's an open dial system without a cap. For some hunters this is not acceptable (personally this is not a big deal to me. Throw a neoprene scope cover on the scope when in the field).
If you fail to move the dial in haste during a hunting situation or the dial gets bumped your cross hairs won't be dialed to the specific distance of the game you're looking at and can be the difference between filling the freezer or not.

Pros: it's really a no brainer for someone to dial in a specific distance, not have to worry about weather your at a specific magnification or weather your hold over is correct. Just throw the cross hairs on your target and make the shot.
The CDS system is SIMPLE. Takes all the guess work out of the shot. Dial in the yardage, put the cross hairs on your target and make the shot.
For Range practice and distance target shooting the CDS system is pretty good. (think about using hold overs at the range for a 400 yard shot on a target. Sure your gonna be on target but are you going to have solid groups? Maybe, many not?) IF you spend a ton of time shooting distance and have hours behind he scope and hold overs are 2nd nature to your eye and brain, sure your gonna have good groups.

In the end, range time regardless of system is the most important. I personally like the CDS system (just my .02). What I like the most is that you can send an older Leupold scope into them to create a CDS dial instead of purchasing a new scope. In most cases it's a 4th of the price. You could even have two CDS dials made (two different bullet weights/loads) for the same scope for half the price of a new scope.

 

[AggieOutlaw]

The CDS is very cool. But I have found myself returning to the good old MOA CDS turret. I like to mess around with different loads so I make a dope card before heading out to the field. The CDS is only good for one load. If you only use one type of factory ammo, it's probably the way to go.

As others said, the scope setting has no effect on point of impact when dialing dope. This is why they are better IMO than fancy bullet drop reticles for hunting.

Explanation: when you adjust your scope turret, you are raising or lowering it by a fixed amount of solid angle (probably MOA or maybe MRAD). This angle corresponds directly to the compensation in muzzle angle regardless of your scope setting. Dial up an MOA, bullet goes up an MOA. 1x, 3x, 9x, 24x...it doesn't matter. An MOA is an MOA. This is why you can sight in your scope at 3x or 9x or 100x...

Contrast that with a bullet drop reticle...if the reticle doesn't change size when you zoom (and most hunting scopes don't, this is called a second focal plane reticle), then the zoom drastically affects the hold over angle. On a standard 3-9x scope with BDC reticle, the angle change at 3x is three times greater than at 9x. So the BDC function of the SFP reticle is only useful at one (usually the highest) magnification. Many scopes perform worst at their highest magnification which is frustrating if you rely on a BDC. I guarantee many animals are lost every year with bullets flying over their backs due to hunters forgetting to set the scope magnification right.

Using a First Focal Plane reticle solves this problem but then causes another. In a FFP scope, the reticle "zooms" with the optic so that the angle subtensions track accurately. This is good because your hold overs on the reticle are always accurate...but it is bad because the result is usually a reticle that is too thick at the high end (blocking field of view) and invisibly thin at the low end. Clever designers work around this but it is nevertheless a problem.

All this to say, that for hunting, I prefer a simple, duplex, SFP reticle with a CDS dial to allow quick and reliable and foolproof accuracy at ranges out to about 500 yards. Never worry about your scope magnification setting. I like to leave mine set to around 250 yards for a 0-300 point blank range...depending on the cartridge. It eliminates potential for error.

 

[noharleyyet]

Good explanation aggie.

 

[1_pointer]

Since the OP mentioned the Windplex reticle, in a second focal plane scope magnification will affect your wind holds as well. I've become somewhat of a fan of first focal plane reticles for longer range shooting, but I've not really put it through the paces too much. One common theme you'll hear from folks that are way more experienced than I in shooting long is to dial for elevation and hold for wind. Many like the FFP reticles for that as the wind holds are the same regardless of the scope magnification.

 

[Jchiggins2012]

Awesome explanations, thank you all very much. I have some choices to make. I dont like having to mess with my current bdc dope card i have. I want to just put my reticle on target regardless of zoom power, set it to 200 yards and take my shot.

Im not a target shooter by any means, and dont intend to be. What scope would you recommend for this ? What reticle as well ?

I forgot to add, is there any companies other than Leupold making this types of dials ?

 

[cahunter805]

I’m confused! Do you want to dial your shots or use a reticle for different shot distances?
If dialing a scope for MOA or a yardage based turret regardless of power it’s the same.
If using a reticle then a SFP changes subtension of the reticle as you zoom a FFP does not.

 

[midwesthunter]

No matter what scope you have, dialing the turrets for correct yardage isn't effected by the change in scope magnification. The only time scope magnification comes into play is if you have some kind of ballistic reticle. Just about every scope manufacture has one of these, either multiple lines, dots, or circles to help with hold over, or windage hole. And only if its SFP (second focal plane) With a SFP scope the ballistic retical is calibrated for a specific magnification.

 

[Jchiggins2012]

Should have been a bit more clear there. I have been using a BDC and I understand the sub tensions change. Thats why I carried my chart taped to my butt stock haha. So I get what youre saying about the CDS system now. Its going to move my turret up or down and regardless of power im in , the cross hairs will be on my target, and I wont have to worry about using my BDC anymore.



Shit I made that way more complicated than I needed to. Just wasnt trackin on the CDS system at first. I am going to go with a CDS dial with the wind-plex reticle, then figure it out from there.







I

 

[cahunter805]

CDS dial with windplex is a good choice. Another thing to think about is are you going to get a custom yardage CDS turret or just dial in MOA for your given range and locations. Once you become familiar with your system it will be like second nature for you. Good luck.

 

[CForest]

CDS dial with windplex is a good choice. Another thing to think about is are you going to get a custom yardage CDS turret or just dial in MOA for your given range and locations. Once you become familiar with your system it will be like second nature for you. Good luck.

I really do like the flexibility with the true cds or just the moa dial. In my 300 I tend to play with loads a lot so have been using the moa setup. But if you have a load you really like and your elevation wont be changing much the cds is the way to go!!

 

[Dakota79]

I hunt in the same area every year pretty much and get along great with my CDS. Same rifle same bullets and pretty much the same environment. If I ever go hunting somewhere else it just takes some range time to figure out the right drop chart without the CDS or you could even order a new one with the correct data.