off by 2 moa at 500

Hopeful I will get some answers here:
Shooting Hornady ELDX precision hunter factory ammo. 7mm-08 150 gr ELDX advertised at 2770
Actual velocity is 2766 with 1 fps spread. Pretty crazy. 5 shots through magnetospeed.
23.5" barrel
1:9 twist
at sea level
75 degrees
BC used 0.298 G7
200 yard zero
2" scope height
Sig Kilo 2400 and Shooter app both agree on drop. 2 moa at 300, 8 moa at 500
actual impact is 2.4 moa at 300 and 9.75 moa at 500
corrected velocity for that drop is 2600 fps. Sounds crazy.

am I doing something wrong?

thanks for the input

snookntarpon said:

Hopeful I will get some answers here:
Shooting Hornady ELDX precision hunter factory ammo. 7mm-08 150 gr ELDX advertised at 2770
Actual velocity is 2766 with 1 fps spread. Pretty crazy. 5 shots through magnetospeed.
23.5" barrel
1:9 twist
at sea level
75 degrees
BC used 0.298 G7
200 yard zero
2" scope height
Sig Kilo 2400 and Shooter app both agree on drop. 2 moa at 300, 8 moa at 500
actual impact is 2.4 moa at 300 and 9.75 moa at 500
corrected velocity for that drop is 2600 fps. Sounds crazy.

am I doing something wrong?

thanks for the input

Click to expand...

User error is the first thing that comes to mind.

How are you measuring scope height?

Are you sure your parallax adjustment is correct?

Are you shooting from the same position ie bench, prone etc when both zeroing and shooting the 500 yds target?

Next would be checking your inputs, specifically the BC. Are you using G1 or G7 BC in your calculation?

Is your program set for running manual inputs for atmospherics or station pressure data?

If your inputs are correct try switching and using the G1 BC and see if it gets you closer to accurate.

I had a similar problem this summer. I got a new phone and you can save your shooter app on there website then install all your old data onto the new phone. After doing this my corrected velocity was 60 less than I had gotten on the crono. Everything was originally proven out and shooting great.

I never found out what had changed and just had to go with the corrected velocitY. It works tho, took a cross canyon 910 yard shot 3" away from aiming point last weekend.

Wild Rose,

Thanks for the prompt reply. caliper is used for scope height, parallax was on at every distance, BC i tried both with no difference. atmospheric data from weather station (airforce base 100 yards from range). The only thing that comes to mind is the the magnetospeed was off, but i measured 2 other rifles and verified velocities that had no drop issues. Dumbfounding.

Thanks livestohunt.
until i get smart on this issue I will just use corrected velocity..
SnT

Generally if your of early in a trajectory your zero needs corrected.

I would verify hat scope height is correct by measuring Center of bolt to center of wind knob. Check your zero at 100. Use the custom drag on the gun profile option. Pull out your phone and sync it with the 2400 and see what it's saying for pressure and temp. Even at that I couldn't see a 1.75 moa difference just based on pressure. You could try changing battery on magneto.

One thing, the advertised G7 BC on Hornady's website is .289 not .298, that will make a slight difference, but not that much.

I ran your other inputs with a .289 G7 and got this out of the GSeven App:

300 yards 2.3 MOA (pretty close to your verified data)
500 yards 8.1 MOA (close to what your apps are saying)

550 yards 9.7 MOA (heck of a coincidence, I would make 100% sure your target is actually at 500 yards and not closer to 550)

Also, the advertised BC from Hornady may be off too, who knows? I doubt many people have tested the 150 ELDx yet.

Anyway, food for thought, hope it helps.

You should be using 2.89 g7 bc for that bullet or less, not 2.98. That might be why your curve is off some, but two clicks low at 300, I think your zero is off also. Especially at that distance, 300 really isn't that far for many variables to be wrong.

I would think the 1 fps spread over 5 shots should tell you something was wrong the magnetospeed. Also did you compare the drops with the Sig 2400 vs a shooting app. I had some issues with sig 2400 and I switched to the 2200 and use a kestrel. Now I never question the data I get.

When I run it I am getting 2.39 Moa at 300 and 8.15 at 500, 9.7 at 550 with a g7 bc. As far as I know, Hornady has been pretty honest with their eld bc's.

Could be lots of things, I would shoot 5 shot groups at paper at both distances and see if that tells you anything. Multiple trips may give different results and that would point to an unseen environmental impact.

Could be hardware, or operator. I have not used a rangefinder with ballistic solutions but part of shooting is feel. Trust what you can replicate in the field.

-Have you done a tall test on your scope to test your turret accuracy?
-Verified the accuracy of your 200 yard zero with precisely measured 300 and 500 yard testing from the same shooting position?.

I have pretty much the same problem as you, My gun is dead on at 100 yards, back up to 300 yards, both the kilo2400 and other apps say 2.4 moa, dial 2.5, shoot and I'm 1 1/2 inches low. I got my velocity using a magneto speed and lab radar, just did another tall target test, scope checks out good, I have measured my scope height multiple time, I haven't figured out what it is yet either. My ammo has a ES of 6 and a SD of 2.3. My next step is to load up a bunch of ammo and go out and shoot, double check my zero at 100 yards, back up 300 yards at a time all the way out to to 1500 or so. Then try to mess with the velocity and bullet BC and see what happens. I just don't get how the calculators think my velocity is over 100 FPS off.

I would guess it's the BC. I thought I read that hornady Box bc is based on 200 yards?