Range Report Shooter and Truing my Velocity

[Outlaw45]

I'm shooting a 7 WSM with 64.0gr of H4831sc under a 168 Berger VLD. I chronographed it with my ProChrono and got an average of 2877 fps. Zeroed at 100 yds. I then took it out to 800 yds to try the TRUING thing. Shooter App said I needed 18.5 MOA. That made me shoot high. I really needed 17 MOA. I used the Muzzle Velocity tool on Shooter and increased my velocity to 2955 fps to get it to equal 17 MOA. I comfirmed trajectory at 300 yds.

So is my ProChrono giving me the wrong velocity? Am I really shooting 2955 fps?

 

[trailrider121]

Re: Shooter and Truing my Velocity

Did You use your Prochrony in good light. I have one and I my best reading between 11am-2pm. Bad lighting can play tricks with chronographs. My 243 win in early morning was getting 2950 avg, then retested in good light and was getting 2998 avg.Something to think about.

 

[Dontmiss0311]

Re: Shooter and Truing my Velocity

I've had the same issue with my chrono and app. I've never paid much attention to the lighting condition in relation to the velocity it's reading. I am starting to think my chrono took a dump on me. I'm shooting a 168gr. A-max over 43.5 grains of Varget, seated to the lands, out of a 20" barrel, and my chrono said it was like 2760 fps. I've only been able to shoot out to 200yds, but when I adjust the MV to my actual point of impact, it puts me at 2680 fps. That's more of what I expected with that load.

 

[Outlaw45]

Re: Shooter and Truing my Velocity

Well I was shooting at about 2pm-3 or 4pm. Your velocity spead isn't near as much mine was.

Do I believe the app and the ballistics or the chrono?

 

[Trevor300wsm]

Re: Shooter and Truing my Velocity

I shoot a 7wsm with a 24" Bartlein barrel 1:9tw
62.9gr of 4831SC
Berger 168VLD
3,032fps from the chrono and confirmed on targets out to 1000yds.

Not sure if it matters or not, but I leave my sky screens on all the time. Never take them off cloudy or sunny. I'm not saying my chrono is dead on, but it's damn close. It's always been close enough to get me on target at distance with it's velocity readings and Shooter app.

 

[Frank Green]

Re: Shooter and Truing my Velocity

Some of the less expensive chronographs from my experience don't always give the most accurate readings. I use a Model 35P Oehler. What I would do is go to the range with a buddy that has another chronograph doesn't matter what model and shoot rounds thru both and see if both agree. If they don't then I would question the chrono.

Later, Frank
Bartlein Barrels

 

[00bullitt]

Re: Shooter and Truing my Velocity

It is rather common that 2 screen chronos will vary by as much as 10% based on lighting conditions.

The Oehler is much more accurate due to its additional screen that helps to lessen error.

The most consistent way to operate a 2 screen chronograph is to seal it up inside a box and use an artificial light source or infrared light kit.

Chronographs are tools that will get you close. They will help you chart linear improvement. But ultimately, the truth lies in where the bullet impacts. But you also need to verify that your scope tracks true and that you are using an accurate BC.

 

[Bronco]

Re: Shooter and Truing my Velocity

I get the best readings on cloudy days, diffused light. Using a ProChrono by Competition Electronics. Also make sure I'm at least 15 ft. from chrono when firing, they can pick up the expelling gas from muzzle. The results must be very close as they prove out when shot out to 1000 yd.

 

[Augustus]

Re: Shooter and Truing my Velocity

I ran rds through a Chrony and an Oehler back to back, the Chrony gave velocities 75 to 100 fps faster than the Oehler. I know for sure one of them was wrong.

 

[Captain Moroni]

Re: Shooter and Truing my Velocity

Where do you find the muzzle velocity tool on Shooter?

 

[Dontmiss0311]

Re: Shooter and Truing my Velocity

Select your rifle and load. Input your data, click on table/graph, then push the option button on your phone.

I'm thinking my chrono is off. The scope seems to track true. I haven't done an actual test yet, but when I shot at 200 yards, I did it with my 100 yard zero and adjusted off that. I also noticed the velocity seemed off when I did some load development for some sub-sonic .308 loads. I haven't had a chance to get out and play with it more lately.

 

[SONIC SAAMI]

Re: Shooter and Truing my Velocity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outlaw45</div><div class="ubbcode-body">Well I was shooting at about 2pm-3 or 4pm. Your velocity spead isn't near as much mine was.

Do I believe the app and the ballistics or the chrono? </div></div>
Have you calibrated your scope?
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/ScopeChecking/

Are you 100% sure that the distances your are shooting are true and measured down to the inch?

 

[Outlaw45]

Re: Shooter and Truing my Velocity

I'm using a Nightforce and I hope it's working correctly. At 100yds I shot a target then dialed 20moa shot again and the distance was 21 1/4". Sounds close right?

I always use the sky screen too.

I think I'll just shoot it again and see what happens.

 

[glocksig40]

Re: Shooter and Truing my Velocity

I used a CED 2 a few times. Used 1 today as a matter of fact. It's accuracy is debatable but so are any of the others. Shot a 20 round string and took average.
I had the same issue today with the Grendle. My calculations said I should be at 10 mils for 1000 but in fact, it took 11.7 to be consistent. I used Kestrel and ballistic iPhone app from 100-700 and they were within .2-.4 mils at each. At 1000 yards it was off by 1.7 mils. I came home and adjusted the bullet BC a little as well as the velocity.
I think the most important thing we both gained was actual DOPE. The velocity from the Chrono and the calculation from the ballistic calculator got us somewhat close. The rounds you got on paper are what tells the story. Now you don't just have numbers to plug in, you have actual dope from the rifle. That's what matters.

SP

 

[SONIC SAAMI]

Re: Shooter and Truing my Velocity

Read this.
http://www.snipershide.com/forum/ubbthre...317#Post3330317

@1000yards/meters and "if" you are using all the "tools" correctly you should be within .10mil or 1/2MOA at any place in the world. Inside 700y you should be spot on.

Last month we went from a DA of 4300 feet here in Vegas to a match in Ash Fork with a DA of 7800.
The cold bore shot for this match was made and hit at 853 yards. The target was a 14 inch steel 7.5 degrees down.

You have got to calibrated your scope.
Get a true muzzle velocity.
A true zero on the rifle.
Ammo with single digit standard deviation is a must(due diligence at the reloading bench).
Calibrated hand held weather station.