CDS tips

[golfer]

Getting ready to send in my order for a CDS dial. I have a ten shot average velocity calculated. What’s the best way to measure sight height? How close does the elevation and temp need to be? I’ll be using a nosler accubond, is the BC listed by Nosler good enough? Any other tips are appreciated.

 

[winmag]

Sight height:

A. Measure scope tube diameter and divide by 2 to get the radius.
B. Measure bolt body diameter and divide by 2 to get the radius.
C. Measure the distance from the bottom of the scope tube to the top of the bolt body.

Add A + B + C.

 

[brockel]

Run your load through a ballistics calculator. Then actually test it to the distances you plan to shoot and see how close it matches up. Adjust from there

 

[golfer]

Run your load through a ballistics calculator. Then actually test it to the distances you plan to shoot and see how close it matches up. Adjust from there

I am guessing this would be done after the CDS dial has been recieved?

 

[brockel]

I am guessing this would be done after the CDS dial has been recieved?

Nope. Verify what a ballistics program says with real world data. All leupold does is plug your data into a ballistics program and burn a CDS dial that matches what the program says. Better to verify with real world data that your actual trajectory matches the ballistics calculator vs finding out later that your barrel alters the ballistics coefficient of the bullet and your trajectory doesn’t match what the calculator is putting out

 

[Fire*guy]

How much does the temp. Into the whole this ? Are we talking an inch with a 50 degree change ? More or less ?

 

[brockel]

How much does the temp. Into the whole this ? Are we talking an inch with a 50 degree change ? More or less ?

Play with a ballistics calculator and see. Then you can decide on what you want your CDS dial parameters for your typical hunting conditions

 

[ImBillT]

A BC listed by Nosler is usually not very good. shoot 5-shot groups at a few different ranges that preferably get pretty far out there for the longest range(500yds is good if possible). Pick the middle of each group to measure drop, and measure as accurately as possible. Then use a ballistic program and adjust the G7 BC until the program gives you the numbers you measured. Give Leupold the G7 BC.

Better yet! Leupold will let you simply give them the number of clicks that you want at whatever yardage you want. Shoot at whatever ranges you desire, and take good notes of how many clicks you had to dial to get to each one, and just tell Leupold that.

Example below:
200-zero
300-11 clicks
400-16 clicks
500-26 clicks

They’ll make that dial for you, no BC or MV necessary. You just have to call instead of using their online order form.

 

[buffybr]

I am guessing this would be done after the CDS dial has been recieved?

Like @brokel posted, you should range verify your load impacts at various ranges BEFORE you have Leupold make your CDS dial.

I have Leupold CDS scope on 5 of my rifles. I have only had Leupold make a custom dial for one of them.

Our range has target berms out to 430 yards, at 100 yard intervals. I have range tested groups for all of my rifles at each yardage and marked that range on the top of the CDS cap on each of my scopes. I first mark with a pencil and then a week or so later I verify the marks and then paint a thin white line on top of the cap for each yardage, and a white dot at the 100 yard zero.

With only 4 marks on the top of the dial it is very quick and easy to dial the range. This pic shows the dot for the 100 yard zero and lines for 200, 300, and 430 yards.

 

[T Bone]

what brockel said!

 

[Wind Gypsy]

A BC listed by Nosler is usually not very good. shoot 5-shot groups at a few different ranges that preferably get pretty far out there for the longest range(500yds is good if possible). Pick the middle of each group to measure drop, and measure as accurately as possible. Then use a ballistic program and adjust the G7 BC until the program gives you the numbers you measured. Give Leupold the G7 BC.

Better yet! Leupold will let you simply give them the number of clicks that you want at whatever yardage you want. Shoot at whatever ranges you desire, and take good notes of how many clicks you had to dial to get to each one, and just tell Leupold that.

Example below:
200-zero
300-11 clicks
400-16 clicks
500-26 clicks

They’ll make that dial for you, no BC or MV necessary. You just have to call instead of using their online order form.

As long as he's not hunting high country mule deer and dialing it in at sea level.

Plenty of pit falls in the cds system so my vote is always to just use MOA.

 

[ImBillT]

As long as he's not hunting high country mule deer and dialing it in at sea level.

Plenty of pit falls in the cds system so my vote is always to just use MOA.

I would also recommend a reticle with mils or MOA, and not even dial, but some people want to dial.

You can buy more than one dial for your scope. Shoot at verifies ranges with the bullet you plan to shoot. Buy a dial for that. Then plug all your info into a ballistics program, and see just how far off you’re going to be at whatever hunt you have planned. If it’s a lot, you can write the difference on a dope chart OR you can call them have them make a new dial with the data based on the altitude and temps you plan to encounter on your hunt. Don’t give Leupold the altitude, temp,, velocity and BC. There are errors in all of those. Just give them the numbers you want based on your actual shooting.

 

[Baerman]

I would also recommend a reticle with mils or MOA, and not even dial, but some people want to dial.

I've considered this but have always wondered if the mil or moa marks change value as your magnification changes. Do the tick marks measure the same between 6 power and 20 power?

 

[Potsie]

I've considered this but have always wondered if the mil or moa marks change value as your magnification changes. Do the tick marks measure the same between 6 power and 20 power?

That all depends on what focal plane your scope is. First focal plane the subtentions will work throughout the magnification range, second focal plane only works at one specific magnification.

 

[bucdoego]

A BC listed by Nosler is usually not very good. shoot 5-shot groups at a few different ranges that preferably get pretty far out there for the longest range(500yds is good if possible). Pick the middle of each group to measure drop, and measure as accurately as possible. Then use a ballistic program and adjust the G7 BC until the program gives you the numbers you measured. Give Leupold the G7 BC.

Better yet! Leupold will let you simply give them the number of clicks that you want at whatever yardage you want. Shoot at whatever ranges you desire, and take good notes of how many clicks you had to dial to get to each one, and just tell Leupold that.

Example below:
200-zero
300-11 clicks
400-16 clicks
500-26 clicks

They’ll make that dial for you, no BC or MV necessary. You just have to call instead of using their online order form.

Where else but here on HuntTalk would you learn this tip? Pretty cool, ImBillT. Thanks for sharing. The whole conversation is an education.

 

[ImBillT]

I've considered this but have always wondered if the mil or moa marks change value as your magnification changes. Do the tick marks measure the same between 6 power and 20 power?

FFP they don’t change.

SFP, they change linearly. If the marks are 2MOA apart at 20X, then they are 4MOA apart at 10X. Most scopes will have the measurements at various powers listed in the instruction sheet in the box. Things can easily be confirmed at the range.

 

[Tikka06]

After going with custom CDS dials on 2 scopes I decided to just try the MOA on my last one. I prefer it. Much more flexible.

 

[Wind Gypsy]

I would also recommend a reticle with mils or MOA, and not even dial, but some people want to dial.

I'm not a big fan of this with a second focal plane scope like the vx series, especially at higher magnification values where the reticle is calibrated at max magnification. Lots of people tend to zoom way in on an animal but I think that is a mistake in many situations. Zoomed way in is more prone to cause issues finding the animal in the scope (especially on follow up shots), shooting the wrong animal, and it's more difficult to spot your impacts. A wider field of view helps you note the body language of the animals around your target animal as well and helps you get a feel for if the animal is more likely to get moving soon.

 

[ImBillT]

I'm not a big fan of this with a second focal plane scope like the vx series, especially at higher magnification values where the reticle is calibrated at max magnification. Lots of people tend to zoom way in on an animal but I think that is a mistake in many situations. Zoomed way in is more prone to cause issues finding the animal in the scope (especially on follow up shots), shooting the wrong animal, and it's more difficult to spot your impacts. A wider field of view helps you note the body language of the animals around your target animal as well and helps you get a feel for if the animal is more likely to get moving soon.

That’s why FFP scopes exist. Nonetheless, you can do it with SFP scopes. If you know how far apart the marks are at any magnification, it’s a simple calculation to get them for all other magnifications. You should also always check your scope against an object of known size and distance just like you should check dialing. There is definitely more opportunity to screw up in the field doing that with a SFP scope.

Manufacturers even included such information about DUPLEX RETICULES before the more complicated reticules became common.

On a side note, I find it a little surprising that a company known for crappy dialing has an entire portion of their business based on dialing. Maybe they’ve fixed it. I haven’t shot a match in almost a decade.