Range Report Truing muzzle velocity

[Curahee19]

Hey gang so I have a 6.5 creedmoor shooting my reloads and both my magneto speed v3 and labradar telling me I’m pushing 140 hybrids around 2820 fps. I realized last match day that my impacts are no where near the 800+ yard targets. So I trued my muzzle velocity for the first time and can’t believe I’ve never done this before to any of my rifles. on my kestrel my trued velocity is around 2885. 65 FPS more than both of those top of the line chronographs. Has anyone had an experience like this ? I’ve always heard of a couple FPS change but nothing this crazy

 

[waveslayer]

True your 600 with Velocity and at 800 try your BC to line up your impacts

 

[StrayDog]

Yep, I zeroed and Magnetoed some new Hornady 6.5 cm 140 ELDM ammo for a match, MV was Avg@2785 from a Bart 26" 1-8 5R.
Got a solid 100y .5 group. and drilled some dots.
Went over to 600 and had to adjust MV down to 2735 to line up the group to the waterline.
I don't have time or place to shoot beyond 600 to prep for matches out beyond 1K yds, so I guessed a reduced g7 bc of .319 and ran with it, lol.
Shot well in the match yesterday, elevation was good out to 1100 yds, the max dist.
Really wish I could true at 800 and 1k after doing 600... but I was satisfied with the 100+600 test and the BC SWAG.

 

[smoothy8500]

More and more it looks like I use the chrono to determine SD's and true the Strelok with real dope.

 

[Curahee19]

I feel like these chronographs are a waste of time now. Just a good starting point but if they can be off by that much everyone should definitely true before shooting a match

 

[Curahee19]

True your 600 with Velocity and at 800 try your BC to line up your impacts

How do you determine it’s your BC that needs truing and not the MV. Because I just did the muzzle velocity and was getting consistent impacts from 200-1050 yards

 

[StrayDog]

How do you determine it’s your BC that needs truing and not the MV. Because I just did the muzzle velocity and was getting consistent impacts from 200-1050 yards

Because BC has little affect at closer range. Okay least far less affect than MV.
You can use JBM to play around with data to see the affects, and many threads on here explaining why. I'm still learning the ins and outs of it all, but it worked well yesterday!

 

[Lawless]

Did a search.

In Strelok pro, how do I true velocity and are there any caveats?

I assume I input the observed difference in impact and it gives me a velocity to input. I tried this with a 10.5” SBR I have zeroed at 53y using a 4” target MPBR and a Unity Fast mount.

Using a velocity of 2650 with Federal M193 the table shows 1.63” high at 100. I entered the actual observed and the velocity changed over 1000fps which seems too much.

It is possible my shooting isn’t precise enough with a dot but the group was under 2” and an average was easy to (sort of) get. I can try again once the weather cooperates, but would like to know the process is right.

 

[6.5SH]

Too short of a distance to true at and a dot is going to add imprecision. You'd need to true between 5-600 yards where it is just entering transonic.

 

[ARShooter91]

I was going to start a similar thread but I'll just post it here. Recently development a load for my 300win mag using the Berger 200.20x, at 1k and 1258yds I'm hitting .2-.3 mil higher than the calculation says. My Tikka is a 1:9 twist shooting those 200s at 3100fps from a 26in barrel.

With that fast twist and speed could I be seeing an increased BC or is my chrony off? I suppose I need to shoot at 600 to verify velocity.

 

[6.5SH]

I was going to start a similar thread but I'll just post it here. Recently development a load for my 300win mag using the Berger 200.20x, at 1k and 1258yds I'm hitting .2-.3 mil higher than the calculation says. My Tikka is a 1:9 twist shooting those 200s at 3100fps from a 26in barrel.

With that fast twist and speed could I be seeing an increased BC or is my chrony off? I suppose I need to shoot at 600 to verify velocity.

The 600 figure was for a 5.56 and a short barrel.
Using the conventional truing methods within the app(s) you'd need to true around 1600 yards.

Assuming you can shoot at shorter distances than your 1258, you can gather precise data and dope your rifle with weaponized math and true up your calculator that way.

A few diagnostic questions; how did you chrono and when and how many rounds? How did you measure your distance? Did you take any incline or decline into account?

 

[ARShooter91]

I used a Pro Chrono that has been checked alongside another with the same results within a few fps. 8rds at 34 degrees for my avg. I used my old MK 7 yesterday and my buddy had his Vortex Razor. I didn't think about angle, it's pretty flat where I shoot but the target probably was a little higher elevation than out shooting position.

 

[Saf3sh00t3r]

Yes!!! The chrono is to get you close, but you always true at 600, then 800…make sure to true BC and shoot 1000 to confirm.

Walk your self back from 1000 back to 200

Any speed works 650 and 850 respectively.

I never use custom curves on my kestrel.

The bullet doesn’t lie - TH

 

[Feniks Technologies]

I’m pretty fortunate. The AB custom curve for the 109’s has been perfect.

At least 5 different lots and all I do is input the velocity from Labradar or Magneto.

I always verify, but have not had to change anything out to 1200yds since Berger released the 109.

 

[ARShooter91]

Alright, buddy said his rangefinder read 1250yds on the angle setting(Elr mode I think on the vortex). That means I was probably closer to .3 mil high.

That'd put the Chrono 70 fps off which I suppose is definitely possible especially with a cheapo. Or the Berger has a .355 g7 or a little of both

 

[6.5SH]

Alright, buddy said his rangefinder read 1250yds on the angle setting(Elr mode I think on the vortex). That means I was probably closer to .3 mil high.

That'd put the Chrono 70 fps off which I suppose is definitely possible especially with a cheapo. Or the Berger has a .355 g7 or a little of both

Purely anecdotal, but 70 fps low is exactly what a friends pro chrono was giving Vs my labradar during some side by side testing of his 77gr 5.56 loads this summer.

He was constantly having flat or blown primers but was stuck on "the velocity was OK".

FWIW his setup habits with the optical were poor; not measuring distance to muzzle nor ensuring it was level.

 

[ARShooter91]

Ha! Certainly see a lab radar in the future for me. I do have it set up parallel to my barrel at my home 100m range and 9ft from the muzzle.

Last year I measured my Grendel with it and my results matched JBM perfectly at 530yds. Idk, I've got some rounds loaded to test here soon. Possibly to 1600yds.