Home Forums Hunting & Shooting Long Range Hunting Trajectory Validation / Velocity / BC

So do you guys check your trajectory and compare it to a ballistic program to validate velocity and BC to tweak your drop charts?

My range goes out to 550 yards, My rifle is zeroed at 100.

What would be a good max range and mid range to check drop? Not sure about being able to shoot a good group at 550 despite hitting steel at that range.

Can I just plug in the drop at those 2 ranges into the app for an automatic adjustment for all the drops? So what gets adjusted, the BC, velocity?

Can someone splain this all to me?

What ballistic app are you using?

Jordan, I meant to include that. I am using Strelok+, which does have a trajectory validation feature.

Edit: would one range be enough?

I think you’ll have to start with an assumed BC and juggle velocity or an assumed velocity and vary the BC.

You can use the trajectory calibration feature of the app, or you can calibrate it manually. If doing so manually, you would modify the quantity you have the least confidence in. So if you're using BC values you belief are reliable, and a chrono that is not so reliable, then you would modify velocities until the trajectory matched your actual results. And vice versa.

If you want to use the trajectory validation feature, the more data points for drops at various distances, the better. But as a minimum, you would need two data points, one being your 100-yard zero and then another drop value at another distance (in your case 550 yards is preferred).

EDIT: To answer your question, I don't have Strelok but it looks like you can select for the app to adjust either BC or velocity in the trajectory validation process. As I mentioned previously, I would select whichever you have the least confidence in.

Gotcha. Thanks

One more thing to be aware of, you should validate your turret adjustment increments before changing muzzle velocity or BC.

Like Jordan says I do a tall turret test to make sure my knobs dial appropriately. Then I would shoot 500 atleast and may atleast check 300 as well. If manually doing it I tend to tweak BC as every rifle is different and bullets can vary box to box. I believe my magnetospeed more then the box label.

The Magnetospeed is a very good chrono, but I forgot to mention that one also needs to consider the measurement sample size when determining how much confidence they have in their average MV value.

Yes, I have done that. Scope is a NF NXS and has proven to have accurate adjustments.

I have a magnetospeed and have questioned my velocity of 2845fps in my 6.5 CM. This is with a 26" barrel, 41.5 grs of H4350 and 139 Scenars. 10 rounds for average velocity.

With 143gr ELD X factory loads, hitting steel at 550 was done with regularity. When I switched to the handload Scenars, I was having a rough time yesterday. This is despite a 3/4 MOA site in at 100 yrs.

I plan on going back with paper, hence the trajectory validation question.

Well I went back to the range this morning and realized that my drop was about 7" more than Strelok showed at 540 yards, 300 and 400 yards were fine.

I dialed up another 1.25 MOA and nailed it. Targets are at 540.

Now I have to figure out if I made an entry error or what else could have been wrong like velocity or BC.

BC changes with velocity. So maybe plug in different bc values over the flight of the bullet?

Comparing the 2 drop charts with a revised velocity of 2772 compared to 2845, the difference gets real noticeable starting around 375 yards. 2772 fps was spit out with the validation adjustment at 540

Since I only shoot out to 540 right now I am going to go with a 2772 MV. It seems reasonable enough for the load.

I am assuming the Scenar BC is pretty accurate? I will try changing the BC, thanks.

Things will be a lot more telling beyond 550. Right now the 1000 yard range is under construction, but I have never shot past 550. Thinking it's a whole new ball game starting at 600.

Thanks for your input. Just trying to learn this stuff

You got your MV from a magnetospeed??


You had to reduce it like 75fps to validate?



Have you tried lowering the BC?? How low do you have to go for your data to validate??


Scope height and all that good stuff is input correctly??


BC from the manufacturer is more of a starting point IMO.



Ballistic calculators and apps are only as good as the information you put in them.

Bryan Litz tested the 139gr Scenars and came up with a .285 G7. If I have a BC Litz provided, I true the muzzle velocity to make it match the trajectory. You might plug in Litz’s G7 and see how it lines up for you.

John

Mauser and Hondo, thanks. After looking at this closer I am a little suspect of Lapua's G1 of 578. Hondo, it looks like I can only change the G1 in Strelok.

I was able to find Litz's G1 at .557 and will plug that in and see if it comes close to matching my drop at 540.

Thank you for all the replies!!

I have learned a lot the past few days and allowed me to expand my shooting skills.

Edit: I know some of Litz's information is subject to copyright laws but some specific numbers are on the interweb

Do you guys have his book?

I don’t use Strelok but would be amazed if it didn’t have a G7 option. Ballistic AE has a library of bullets Litz has tested with their associated G7 BCs. That’s where I get the BCs if available. If using a Litz provided BC, I always true the velocity at the farthest I can shoot on my range (820 for now). That has always worked out pretty well for me.

Litz did several podcast on “The Everday Sniper” podcast, and they were very informative. G7 is the way to go for BCs if you can get it. Velocity banded G1s like Sierra does work well if your software can process that. Single G1s are least preferable because the G1s decrease markedly as velocity decreases.

John

The G1 BC is based on a poor drag model for the shape of the Scenar. Your MS velocities are likely very accurate, so I would use the Litz G7 BC value and tweak as necessary to match your actual drop data. Like John said, I’d be surprised if Strelok didn’t have the capability to use G7 BC values.

I just checked and don't see where I can change from G1 to G7 on Strelok +. I also have Strelok Pro, which does have the capability to use G7. Strelok + satisisfied my needs so I hadn't use the Pro application.

Now that I am in the rabbit hole, I will transfer to Strelok Pro and see what I come up with.

EDIT: using Litz's G7 and my original velocity, I am right about where I should be. 10.6 MOA using my original velocity vs. 11.0 MOA using a 73 fps reduced velocity.