Need help making a drop chart...

[Seeking_Coyotes]

I recently bought a .260 Rem. and Nightforce ACTAR MOAR (minute of angle). I am new to dialing and would be very, very, grateful for some help.


Sighted in the scope at 100, 200, 300. Here are my dial numbers before making the 100 yard elevation adjustment zero on the dial.


100 1.75

200 3.75

300 6.25


After I move the cap to set 1.75 to zero, these will be my dial numbers I believe.


100 0

200 2

300 4.50


How do I know from this data what my scope settings will be out to 500 yards given my muzzle velocity of 2,556 fps. and bc of .585


I ran a chart on my Sierra Infinity Ballistics Software but it only tells me drop and such without any conversion for the scope dial numbers at each yardage. I don't understand how adjustments change every hundred yards (ie. 1 click is 1/4 inch at 100 yards and 1/2 inch at 200, etc.) I think. So, how do I convert my drop chart based on inches from the Sierra program to dial numbers on my scope?


Also, a graph I did says it will be moving at 1,900 fps. at 500 yards. Will I have enough speed to shoot this bullet out to 1,000 yards before it feels the effects of the transsubsonic barrier or whatever the speed is that causes instability dropping below the speed of sound.


Please help.
:-\

 

[ninehorses]

https://www.youtube.com/watch?v=VA2PZBD5Tjg

Understanding MOA

 

[CatShooter]

I recently bought a .260 Rem. and Nightforce ACTAR MOAR (minute of angle). I am new to dialing and would be very, very, grateful for some help.

Sighted in the scope at 100, 200, 300. Here are my dial numbers before making the 100 yard elevation adjustment zero on the dial.

100 1.75
200 3.75
300 6.25

After I move the cap to set 1.75 to zero, these will be my dial numbers I believe.

100 0
200 2
300 4.50

How do I know from this data what my scope settings will be out to 500 yards given my muzzle velocity of 2,556 fps. and BC of .585

I ran a chart on my Sierra Infinity Ballistics Software but it only tells me drop and such without any conversion for the scope dial numbers at each yardage. I don't understand how adjustments change every hundred yards (ie. 1 click is 1/4 inch at 100 yards and 1/2 inch at 200, etc.) I think. So, how do I convert my drop chart based on inches from the Sierra program to dial numbers on my scope?

Also, a graph I did says it will be moving at 1,900 fps. at 500 yards. Will I have enough speed to shoot this bullet out to 1,000 yards before it feels the effects of the transsubsonic barrier or whatever the speed is that causes instability dropping below the speed of sound.

Please help.
:-\

The click values on your scope are in MOA, NOT inches, so it is 1/8 moa, or 1/4 moa... NOT 1/8 inch, 1/4 inch

My Infinity program shows drop in both inches, and MOA.

If yours doesn't, then read the manual and make the changes in the display that you need.

Then it is a simple range, dial, and shoot.

Sierra has an outside company test each bullet and assign BC's according to actual drop, so Sierra bullet drops are amazingly accurate when used together with the Infinity software.

There is no sonic instability to worry about - people are shooting at 1,500, 2,000 yards and further, without their bullets wondering off and getting lost. I have shot to 1,900 meters (2080 yards) with no problems.

 

[Alexander-M]

You can also use the Hornady Ballistics Calculator:
http://www.hornady.com/ballistics-resource/ballistics-calculator

The attached image is a sample of the calculator output. I entered some data that may not be correct, such as the bullet weight, and opted for a 5-mph wind just as an example. Note it provides bullet drop in inches and comeups in MOA and MILS, as well as wind drift values.

Note - For wind data, select 'advanced' instead of 'basic'.

Good luck!
Nando

 

[lpreddick]

another vote for the hornady ballistic calculator. i discovered it years ago, now they have an "advanced" calculator that lets you add more variables. it's accuracy amazes me in that i entered data for my 6-284 shooting 105 bergers and dialed in a 532 yd ghog and the bullet hit exactly where my scope told the bullet to go, based on the number of min of elevation from a 100 yd zero. one word of caution: the program has "sight height" already entered as "1.5 in" and none of mine were 1.5 in, so my long shots were off until i entered the sight height of my guns, some being 2.2 in. and more. i take their data and print a card giving a range for every click of my scope's elevation knob. range a ghog, find that range on the card, click up the number of clicks for that range and DRT...the wind is another story.

 

[Seeking_Coyotes]

Wow...this is a tremendous help! Thank you.

yes, my sierra infinity chart looks the same. I thought moa being 1/4" at 100 is based on inches? Can you help me understand this better?

I was thinking that although the chart gives me drops in minute of angle that I couldn't just do what you suggest because the mathematical multiplier effect of moa being like 1/4 at 100 yards but 1/2 at 200 yards, etc. I have difficulty understanding math though...

Will check out the Hornady ballistic calculator.

Now if only I could find some 140 Amax somewhere so I could keep shooting. Oh, well, the groundhogs are smiling with the shortages...

 

[Seeking_Coyotes]

Your chart is showing a drop of 19 moa at 500 yards. If you were/are using a 1/4 moa scope, does that mean you need to come up 76 clicks from your zero to be on at 400 (4x19)?

 

[NateHaler]

yes, that's what that means. And if your scope featured 1/8 MOA click adjustments, you would need 152 clicks to add 19 MOA elevation.

Turn those knobs people; they really do what they are supposed to. Leave the holdover guesstimating for Dan'l Boone and/or grampa with his deer rifle.

 

[Seeking_Coyotes]

If your adjustment know has the number 19 on it, assuming 1/4 nightforce moa, can you skip counting and just dial it to the 19?

 

[brian427cobra]

JBM Ballistics is all you need

And don't EVER count clicks, need 20.5 MOA, turn the knob to 20.5 MOA, when your done shooting get in the habit of a post shot checklist, the first thing should always be returning the scope to zero.

 

[CatShooter]

Turn those knobs people; they really do what they are supposed to. Leave the holdover guesstimating for Dan'l Boone and/or grampa with his deer rifle.

;D ;D ;D

Zero your rifle at 100, set the turret at "0"... and then just dial the ranges - no one counts 178 clicks - your scope will have 1 moa lines on the turret, and then small lines for the clicks - so if you have 19.75 moa and you have 1/8 clicks, dial 19 and then 6 more clicks.

Ping, dial, and shoot!

 

[Erik Cortina]

Using clicks on scopes is like using pennies when talking about $100.00

Subtract 1.75 from all your numbers, just like you did with your 100 yard zero.

If the chart calls for 7.5 MOA, just dial your scope to 7.5 and shoot.

 

[Seeking_Coyotes]

Thanks all. I ran my numbers using my Sierra and the Hornady. The actual values are perfect at 100 and 200 but at 300 I was right on at 4.5 from my actual shooting notes but both programs are saying 5. Guessing this means that I will not be able to use the data on the charts. I'm going to shoot the gun at 400 and 500 to get the actual numbers compared to the calculated numbers from the chart. Is there a way to plug the ballistic calculator so it will show my actual moa adjustments at 300, 400, and 500 and then maybe the other numbers on the chart will be on?

 

[CatShooter]

Thanks all. I ran my numbers using my Sierra and the Hornady. The actual values are perfect at 100 and 200 but at 300 I was right on at 4.5 from my actual shooting notes but both programs are saying 5. Guessing this means that I will not be able to use the data on the charts. I'm going to shoot the gun at 400 and 500 to get the actual numbers compared to the calculated numbers from the chart. Is there a way to plug the ballistic calculator so it will show my actual moa adjustments at 300, 400, and 500 and then maybe the other numbers on the chart will be on?

Bullet companies don't derive their BC numbers the same way, and chronographs are not as accurate as most people think... and the software may not get a shooting solution the same way.

It is often necessary to "tweak" the velocity to make the drop chart match reality.

If you are shooting a 4.5, and the software says 5, then increase the velocity until your software says, 4.5 Then make your next tests at 300, 400, and 500... if it doesn't match, then tweak again.

IF you get to the point that the drop curve matchs at 100yds and 700yds, but 400yds is high or low, then tweak the BC number... if the midrange hits higher than the software, then lower the BC... and visa-versa.

You can get it right so it tracks perfectly.

 

[Seeking_Coyotes]

Thank you CatShooter. Very helpful. 8)