How Accurate are Range Calibrated Turret Knobs?

[edward hogan]

How accurate? Close enough for Gov't Work might be the realistic answer, but... Just let's say you have static conditions (never varying) so your bullet flies the same path every shot. Very impractical, even to attain ammuntion made to exact same parameters. Primers and powder vary too much by lot. Uncle Sam can spec identical burn and pressure rates for his ammo, but realistically we can't. So there's that...

What really matters is your scope mount setup. Is your scope base mounted truly perpendicular on your receiver? Is your barrel perfectly shouldered to a perfect receiver shoulder? How do you know? If your setup is canted or off by a fraction at the muzzle, then what's the variance at distance? Not to mention, your zero is only capable of precision track at the exact impact distance. You bought the scope or dial system to be ON at whatever distances you select, right?

Lots of luck... Tons of luck more precisely... Or maybe you own a scope boresighting-collimator tool like the Bushnell 74-3333? Think your $200 Pic rail is good? Best Prove It... Think your scope rings are good, Prove It. You're proving this for yourself, so you have a starting point...

The whole dial and dump turret idea came from the Leupold Ultra with M3 turrets. These and the later Mk4 M3 scopes are very tough and capable, although no longer esteemed by tyros because they don't got "great glass". The military ain't concerned with putting their round through the left thread hole in the 2nd from top button... Most tyros are. A hit is the goal. Sure, you can extrapolate and project all your expectations on the scope, but scope can't do anything well if its mount is off perpendicular.

The Bushnell 74-3333 is the best gun tool I ever bought, back in `91. Helped me diagnose an off-center slotted expensive scope base. Helped me prove that the LaRue QD risers I was using on AR-10s was 20moa off-center at bore, while the integral Pic Rail on the Armalite rifles were about perfect. Also proved that Leupold QR mount systems were not "on", while cheap Weaver bases on same rifle receiver were. Testing between 3 or more receivers does establish the receiver tap job or integral bases were fully correct.

Not to bust the bubble, but once you've proven your mount setup, then it's time to move onto the scope. If the scope is precisely mounted and the turret moves reliably, comes down to matching your handload formula for ammunition, and maybe re-marking your turret with an ink pen or engraver.

 

[Benjaminwill80]

Was speaking with Leica about the geovids and the gentleman had an interesting method for using those with a custom dial. He said the geovid is calibrated at sea level and can't quite remember the temp but think 58 deg or 65 deg, somewhere in there. Anyways, he said if you have your dial made with same parameters the geovid is calibrated to, the dial will then be calibrated to the geovids. That way when you range with the geovids it calculates the appropriate adjusted range based on the atmospherics. Because the dial is matched to the geovid calibration, the range output of the geovid can be used with what is on the dial regardless of your elevation, temp, etc.
I've not tested this but seemed like a nice setup.

 

[codyadams]

Was speaking with Leica about the geovids and the gentleman had an interesting method for using those with a custom dial. He said the geovid is calibrated at sea level and can't quite remember the temp but think 58 deg or 65 deg, somewhere in there. Anyways, he said if you have your dial made with same parameters the geovid is calibrated to, the dial will then be calibrated to the geovids. That way when you range with the geovids it calculates the appropriate adjusted range based on the atmospherics. Because the dial is matched to the geovid calibration, the range output of the geovid can be used with what is on the dial regardless of your elevation, temp, etc.
I've not tested this but seemed like a nice setup.

That is exactly what the G7 rangefinder does, except you can have your turret made however you want, and calibrate your turret atmospherics into the rangefinder, then it outputs the appropriate adjusted range based off real time atmospheric conditions. It also spits out MOA or MIL adjustments.

 

[Bman940]

I finally found this pic of the custom turret on my .257 WbyMag. Zero is 200 yards and I have hit soda cans at 600 yards by just dialing in my distance. The scope is a MONARCH 3 4-16x42 Custom XR Turret. Glass is very clear throughout all magnification levels.

 

[codyadams]

I finally found this pic of the custom turret on my .257 WbyMag. Zero is 200 yards and I have hit soda cans at 600 yards by just dialing in my distance. The scope is a MONARCH 3 4-16x42 Custom XR Turret. Glass is very clear throughout all magnification levels. This is a second focal plane scope so the custom turret only works at max magnification.

Why would the turret only work at max magnification......say 5.5 MOA corresponds to 425 yards, so if you dial 5.5 MOA (or 425 on your turret), you just dialed 5.5 MOA at 4x, 7x, 14x, 16x, it doesn't matter the adjustment is the same. Your magnification doesn't matter. If you had a holdover reticle however, it would matter.

 

[Bman940]

Cody, you are correct. I was multi-tasking and thinking of the BDC reticle which unless on a FFP scope changes the corresponding distances related to magnification. Thank you for making me aware of my error, I will change it.

The bottom chart of this screenshot shows the distance differences when changing magnification.

 

[codyadams]

Cody, you are correct. I was multi-tasking and thinking of the BDC reticle which unless on a FFP scope changes the corresponding distances related to magnification. Thank you for making me aware of my error, I will change it.

The bottom chart of this screenshot shows the distance differences when changing magnification.

We all get distracted!! Ha ha. I was fairly certain the reticle is what you meant, just wanted to make sure that less experienced readers wouldn't get confused.

 

[Bman940]

We all get distracted!! Ha ha. I was fairly certain the reticle is what you meant, just wanted to make sure that less experienced readers wouldn't get confused.

Much appreciated! Just like with a custom turret, using Nikon's BDC reticle and Spot On is dependant on the shooter entering the correct information into the program to get the best results. I have helped Nikon out with numerous shooting event's where guys new to the BDC reticle have hit 4-inch jars of tannerite at 627 yards using Spot On and the BDC reticle. Pretty fun watching the faces of guys who were sure the reticle was marketing voodoo make it work and even cooler when they say they would buy one!

 

[GMHVAC]

Save all the hassle of the dope cards ( keep them for a back up)and get the G7 BR2 like the previous post said. Takes altitude, inclination, temperature out of the equation. You just need to plug whatever your turret info is into the rangefinder and then you are set. All good as long as the batteries are good.

 

[Doug Herold]

Thanks for the response

I should have added that I do only use one load and will use the gun in the same conditions.

Thanks for mentioning that.

If you shoot 600 yds or less your POI should not vary enuf to make a difference in a big game animal.

 

[Greyfox]

One of my rifles, a Cooper/Huskemaw 6.5x284 with a Custom Turret Tape, an accurately calibrated tape that attaches to the turret. It's a very cost effective(<$25For 3 tapes and a wind chart) approach. It is calibrated to an average set of conditions that I hunt for 'yardage", and includes an "MOA" scale along the lower portion(shown below). At 500 yards or less across a wide range of atmospheric conditions, POI is accurate to +/- 1 click(.33MOA) at 500 Yards. For shots beyond 500 yards, using measured atmospherics, I will revert to the MOA scale. I have found this system to be exceptionally fast, accounting for precise shots on game to 1200 Yards, varmints further. While I prefer using the MOA scale for the +500 yard shots, as has been mentioned, the Gunwerks G7 RF, when programmed for "yardage" compensation, and using a yardage turret calibrated for a given set of conditions, will calculate an 'adjusted" yardage value that are compensated for atmospheric changes. If I choose to use another system of ranging and ballistic calculation(Terrapin/Kestral, Sig 2400 etc), my MOA scale on the turret is utilized. I would add that I have also used the Kenton Turrets, with the same turret approach, and equal success.

 

[lyotehunter]

%of error Hensoklt 3.5x26x56 o.o%,kahles o.o%,us optics 0.0%,valdada 4x28,0x0%,nightforce beast,0.2%,nightforce atacr (second scope)0.4%, schimidt&bender 3x27 0.8%,vortex 5x20x50 1.1%,% of error in elevation adjustment.so to stretch it out to 3000yds.2.5%error would land you 10 feet off target based on 375cheytac ballistics.this is how far the turret it's self is off.

 

[L.Sherm]

I like to keep it simple, range, dial my turret to the yardage that my range finder says. It's worked out to 890yds so far. That being said I believe you need your rangefinder, scope, load and rifle as one package, if you change one thing start over.