Update: Zeroing And Subtensions, Calibration Distance?

[tony270]

If the rifle is zeroed by shooting at a target 50 yards away, and the bullet trajectory is known, can the zero be changed to 100 or 200 yard without shooting using the elevation adjustment?

The reason that I ask is that the subtension hash marks are calibrated at 200 yards. The rifle is zeroed at 50 yards, but I can't get a quarter size shot group with a 6 power scope at 200 yards
(vortex razor 1-6x24 hd gen2 jm-1 bdc reticle, with 20 moa cantilever mount, on an REC-7 DI 5.56 AR).

I need a spotting scope, but until then I will exercise to check my targets, that's why I didn't take anymore shots.

Here's where I'm aiming with the 50 yard shooting zero (red crosshair), at this 400 yard target, and where the the rounds are hitting ( blue circle area, low and in front of the target). If I could dial-in the 200 yard zero using the known trajectory, I could simply use the subtension for 400 yards, instead of Kentucky Windage, is that how it works?



The blue pointer is a 100 yard target, the red pointer is the 400 yard target.
.


A view from the target, to the shooting position (oom in to see).

[SAD338]

For the Razor, I usually zeroed at 50 yards and then fine tuned at 200 yards. And even then, it's not a quarter sized group. More like 2" using 77gr SMKs.

[smoothy8500]

I quit using 50yd or 25yd "zero's" a long time ago since they always were a ballpark estimation. Confirm everything at the instructed distance (200yds for you) even if it's a 3-4" group. In theory, it should be correct (so many mil or MOA up for 200) but even if you adjusted the scope based on your 50yd results, it is still a guestimation of results at distance. It's worth making a poor man's Shoot 'n See target with bright colored cardboard, packing tape, and black paint to see your impacts even with a spotting scope.

[HK Dave]

Do you have software that helps with this like Ballistic, TRASOL, Bulletflight? It might shine some light on your question.

[lordmorgul]

[lordmorgul]

Based on pic #1, you have a reticle hold off center so assume windy day, and target hits with quite a bit of horizontal stringing so likely not a steady breeze.. I think maybe you just need to go shoot again?


Andrew - Lancaster, CA
NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / NAGR / NRA-ILA contributor, USCCA member

[Mute]

Always confirm at the distances you intend to shoot. Even if the theory is correct, nothing beats hard, real world data. Also, regarding group sizes, are you certain that:

1. Your gun is capable of the groups you wish to see
2. Are you capable of shooting those groups at those distances

My own experience with the Vortex HD II 1-6x is that the bdc reticle is fairly spot on. I used mine with a 50 yard zero.

[HooYah]

I zero mostly everything at 100 yards. With the Tremor/Christmas Tree reticles, it's all holds anyways, so I'll use a ballistic calculator to get my DOPE.

[tony270]

I want to thank each and everyone that replied, it all helped me.

Hi lordmorgul, this is my setup:
Vortex Razor HD Gen II 1-6x24 JM-1 BDC reticle, mounted with a Vortex Precision 20 MOA Fordward Cantilever Mount, shooting a Barrett REC-7 DI 5.56 AR.

I walked off the distance, one thing I noteed is that the flight path takes round about 2 feet or so from the ground as it travels to the target, this happeneds about 40 yards away from the target. Being so close to the ground, I don't know if that makes the round float a bit. When I aimed on the bullseye, it looked like and sand was flying high and right of the target, and when I went and looked I could in fact tell that by the marks on the sand. I adjusted, and the sand started flying in front of the target. I adjusted again until the sand stopped flying, at that point I knew that I was hitting paper.

I need to download the app, and I need splatter targets and spotting scope. I'm using Federal American Eagle Factory ammunition, so I know the bullet fps and trajectory characteristics, would I still need a chronograph? The target could be farther, I need a range finder, that's for sure. The breeze was maybe 3 mph, from right to left.

Could I use this ballistics calculator from Federal, that's the ammunition that I using?

https://www.federalpremium.com/ballistics-calculator

I can shoot a 4", 3 shot shot-group at 200 for that zero, then pick a application software, yes, 50 yards is the battle zero that I have used.

Thanks Again.

[Mute]

I want to thank each and everyone that replied, it all helped me.

Hi lordmorgul, this is my setup:
Vortex Razor HD Gen II 1-6x24 JM-1 BDC reticle, mounted with a Vortex Precision 20 MOA Fordward Cantilever Mount, shooting a Barrett REC-7 DI 5.56 AR.

I walked off the distance, one thing I noteed is that the flight path takes round about 2 feet or so from the ground as it travels to the target, this happeneds about 40 yards away from the target. Being so close to the ground, I don't know if that makes the round float a bit. When I aimed on the bullseye, it looked like and sand was flying high and right of the target, and when I went and looked I could in fact tell that by the marks on the sand. I adjusted, and the sand started flying in front of the target. I adjusted again until the sand stopped flying, at that point I knew that I was hitting paper.

I need to download the app, and I need splatter targets and spotting scope. I'm using Federal American Eagle Factory ammunition, so I know the bullet fps and trajectory characteristics, would I still need a chronograph? The target could be farther, I need a range finder, that's for sure. The breeze was maybe 3 mph, from right to left.

Could I use this ballistics calculator from Federal, that's the ammunition that I using?

https://www.federalpremium.com/ballistics-calculator

I can shoot a 4", 3 shot shot-group at 200 for that zero, then pick a application software, yes, 50 yards is the battle zero that I have used.

Thanks Again.

Use JBM for the ballistic calculations.

[lordmorgul]

[lordmorgul]

[tony270]

So I went back out and retested the subtension lines for 400 yards. I shot 10 rounds and 8 hit the 12 in target at 400 yards using the correct hash mark for that range, 50 yard zero, 16" Carbine, clam conditions, 20 MOA mount. The Vortex set-up on the REC-7 DI is almost as good as it gets.

[k1dude]

Off topic, but I would suggest a better place to shoot. You have no observable backstop. Who knows where those bullets are going. I would suggest getting much closer to those those hills in the background.

[tony270]

I can see the bullets drop in the sand dune, I can also see beyond the dune all the way to the hills. You can't see the true perspective in a picture, always know my target and what's beyond it (the backstop).

Thanks