Rifle Scopes Is my scope tracking correctly

[jcann]

I have a Vortex Razor Gen 1, 5-20x50 and I need your opinion as to if it's not tracking correctly. I'm leaving Oct. 5 for a Colorado antelope hunt.

First time out after sighting it in I took it to 455 yards. Shooters App gave 2.0 mils elevation. I only needed 1.8 mils on the scope to get on the 10" gong.
Today I was shooting 910 yards. Shooters App gave 6.1 mils elev. & 1.3 mils wind. I only needed 5.5 mils elev. & 1.2 mils wind to get on the gong.

If I go into the App and change both the elevation/wind correction factor from 1 to 0.9 I'm almost nuts on to what I observed while shooting in the field.

Does it sound like my scope isn't tracking correctly. There is no way I can get back out to the field to run a tracking test before we leave.

I'm shooting:
7wsm
180 gr. Berger Hunting VLD
2920 FPS
1:8.7 twist
1.9" scope height
DA 2920

Thanks

 

[Sheldon N]

Model of chrono? Seems more likely that your velocity is closer to 3000 fps than 2920.

 

[SPAK]

If you don’t have a way to verify tracking you can carefully clamp your rifle in a heavy bench, point it at a brick wall and line up the 10 mil mark on the reticle even with a brick line. Run your turret 10 mils and watch in the scope to see if it lines up with that brickline you initially utilized on the 10mil line. Then then back to zero, confirm it went back to zero and the 10 mil is back on the same brick line.

Make sure your parallax is adjusted for, and use a brick wall that is at least 50 yards away.

It’s not as good as a true scope tracking test but it will show gross errors.

The early gen I razors had some tracking issues that were very quickly fixed by Vortex. Tracking was off by .2 mil at 10 mils. I found an issue with mine when I first purchased and had new turrets within a week. Problem solved. That was probably 8-10 years ago.

That being said, even with an early model turret it wouldn’t show the discrepancy you are seeing. More likely velocity, bc, scope setup/zero. Also make sure your mounts are tight...

 

[jcann]

Everything is tight concerning scope attachment. Chronograph is a Magnetospeed. We used it for my sons 260 Rem to get velocity and his data was correct at 910 yards

 

[Sheldon N]

Chronograph is a Magnetospeed. We used it for my sons 260 Rem to get velocity and his data was correct at 910 yards

Perhaps sentivity setting or position affected results? I've had to adjust sensitivity going to larger bullets/calibers.

Velocity just seems the like far more likely cause. The alternative would be that the thread pitch inside your scope erector is massively wrong, which would be a machining/tooling error that would be highly unusual.

 

[NateVA]

Seems more like a difference between the app and reality in DOPE rather than an error in the scope.

 

[SPAK]

Use hold over in your reticle and see if it’s the same result...

 

[BigJimFish]

You can't isolate the two variables (real dope vs calculated dope and real tracking vs ideal tracking) when you are testing them together. You can:
1) Forget about caring where deviance from the calculated ideals is coming from, draw up a drop table based on measured field data, and use that.
2) Run a real ladder test on the scope, ideally with some sort of humbler device to remove shot to shot deviation, find out the magnitude of deviation in the scopes adjustments, and then add that into you ballistic program to make it a little more accurate. (you probably have less than 2% deviation from spot on accurate in that scopes adjustments.)
3) Fudge the velocity numbers around in your calculator to get it to act more like reality as measured by your scope, chrono, and rangefinder (really, this tends to be pretty effective.)
4) Get a ballistic calculator that allows for better fitment of a calculated curve with real world data inputs. (some are better than others and I can't say I am fully happy with any that I have used.)

Basically, I doubt that your scope has that much to do with the issue you are having with differences between the app and your measured dope. I can't tell you exactly where all these errors between calculated and actual dope come from, there are a lot of potential sources, just that I have often found them though yours is bigger than I am used to seeing so maybe one of your measurement instruments is a bit off.

 

[Hairy Biker]

What BigJimFish says.

Shoot it more, record the DOPE, plot the variation and crack on.