MOA adjustments?

hoochie

hoochie

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just got a new scope with 1/2 MOA turret (Vortex Viper HSLR)

shooting a 270WSM, 140gr SST @2900 FPS, BC .495 zero at 100

used Hornady and Sierra calculator, getting different "come ups".
I said 100-600yds, but the calculations differ by about 4 MOA for the same distance. Am I doing something wrong with the software??

Just got the scope mounted and zero'd today, havent had a chance to get out for any distance yet, but wanted to get an idea of what my come ups should be.
Help?
Thanks
 
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Quite a few factors affect required elevation that may or may not be factored into both calculators. Some of those factors may be set differently. I have the basic free version of strelok that says 12.18 moa up from 100 to 600 yds using the load specs posted and weather matched to my location. Your best bet is to hit the range, zero at 100 and figure your come ups in steps using local weather info. 100/300/600 should be pretty easy to figure out keeping you on paper so you're not pissing shots into the dirt.
 
At 600y, that's a difference of a couple of feet.
You'll be starting at the shorter ranges, and as you move back, you will get a good idea of what is actually happening.
 
hoochie said:
just got a new scope with 1/2 MOA turret (Vortex Viper HSLR)

shooting a 270WSM, 140gr SST @2900 FPS, BC .495 zero at 100

used Hornady and Sierra calculator, getting different "come ups".
I said 100-600yds, but the calculations differ by about 4 MOA for the same distance. Am I doing something wrong with the software??

Just got the scope mounted and zero'd today, havent had a chance to get out for any distance yet, but wanted to get an idea of what my come ups should be.
Help?
Thanks
Click to expand...

Possibilities to check:

- make sure that you are asking both to the Hornady and Sierra ballistics programs to calculate your drops at 100-600 *YARDS* (if one were doing the calcs for 600 yards and the other was doing the calc for 600 metres, that would be your explanation right there)

- is the "scope height above boreline" set the same for each?

- are you using a "G1" bc of 0.495 for each program? (make sure you're not telling one of the programs that your bullet has a G7 BC of 0.495)

- make sure that each program is using the BC that you are giving it, and not the BC it thinks the bullet has from a library of bullets.

- are both programs using 2900fps MUZZLE velocity, or is one of them quietly considering it to be 2900fps INSTRUMENTAL velocity and quietly upping your muzzle velocity to make things work out? (INSTRUMENTAL velocity is the speed of the bullet over a chronograph 15' or sometimes 75' downrange)

- are you using the same air temperature, pressure and elevation for both programs? (though this won't be enough to give you a 4MOA error at only 600y)


As for your question, these figures (in GREEN are the MOA drops from 100y) from JBM will be good enough to get you on paper from 100y-600y (likely within a half MOA at each distance):

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
100 -0.0 -0.0 0.7 0.7 2687.2 2.407 2484.9 0.107 18.9 18.0
200 -3.3 -1.6 3.0 1.5 2476.0 2.218 2109.5 0.224 39.4 18.8
300 -12.3 -3.9 7.1 2.3 2274.3 2.037 1779.9 0.350 61.6 19.6
400 -28.1 -6.7 13.2 3.2 2082.7 1.865 1492.6 0.488 85.9 20.5
500 -51.9 -9.9 21.6 4.1 1900.4 1.702 1242.8 0.639 112.4 21.5
600 -85.3 -13.6 32.6 5.2 1726.1 1.546 1025.3 0.804 141.6 22.5
 
thanks guys. Seems that the info you have posted is what Hornady calculator gave me. I have to recheck what the heck I was doing with my Sierra I5 program, cause it was giving me the come up for 600yds, but telling me to use that come up for 400.
My scope has a "dead hold BDC", but the incriments on it are 100yds. I want to learn to use the dial so I can get a more accurate shot at a range between the given hold points.
I'll get it!
 
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