Help calculate muzzle velocity and drop

[sasquatch]

So, I don’t know if this is even possible, I’d assume it is. But here goes

I do not have a Chronograph to run calculations, however I have shot a few different yardages and have the measured drops to reference.

I am hoping to figure out from these bullet drops what the muzzle velocity should be to achieve these known drops. I figured if anyone can it’s one of you guys.

I am shooting a 280 AI. The ammo is loaded by cooper creek. The bullet is Hornady 162 gr ELD-X

Now, the ammo box says 2970 for the muzzle velocity, but comparing to the bullet drop on the ammo box what I am achieving cant be right.

With a 100yd sighted zero, I am 3-1/4" low at 200yards, and then 13.5" low at 300yds.

i am wondering what kind of true velocity i may be getting and also from this what should my 400 and 500yd drop be??

This picture is of the manufactures calculations. The drops I got are like 50% more than they say it should be

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[hereinaz]

Look up Gravity Ballistics. It’s specifically for calculating actual drop off of data you provide.

 

[hereinaz]

I still question the moon landing, your existence and whether aliens crashed at Roswell.

 

[Bluumoon]

Either of these two will do it. You’ll get better data the further out you can plug in before going transonic.

 

[MuleyFever]

Download a ballistics calculator and input your bullet data and weather then play with the velocity until it matches your drops. Make sure the sight over bore measurement is correct.

 

[sasquatch]

Thanks fellas, looks like I’m only coming up with like 2720 FPS

Seems really slow for the caliber.


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[Koda_]

I came up with the same 2720mv as you. If your actually getting -3.25" drop at 200yds then your mv is not 2970fps. That said, Ive never had factory ammo live up to its advertised velocity. If your going to hunt past 300yds then you need to buy a chrono because you also don't want to hunt past the bullets terminal velocity, especially with that low of a muzzle velocity.

Here's a link to your data out to 500yds but it wont be precise without your altitude and actual mv average.

ShootersCalculator.com | Ballistic Trajectory Calculator

Calculates the ballistic trajectory of a bullet fired from a rifle, handgun or other firearm. Produces a ballistic trajectory chart and table that shows the drop, velocity, kinetic energy, windage, and trajectory of a bullet.

shooterscalculator.com

 

[hereinaz]

Thanks fellas, looks like I’m only coming up with like 2720 FPS

Seems really slow for the caliber.


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Bullets don’t lie.

If it’s not the bullet, then it’s something else. Some things to consider as I think out loud for exclusion. Hard to see one of these as being the sole cause, but I would scratch my head too…

Is your barrel slow?
Was it extremely cold when you shot? Is the powder temp sensitive?
What is your barrel length vs. the box barrel?
How are you shooting and measuring drop?
If dialing, does your scope dial accurately?
Is it actually 200 and 300 yards?
Is your 100 yard zero perfect?
How many rounds did you shoot to verify your drop numbers? How large were the groups?
Did you change positions drastically to shoot the different yardages?
Have you asked Copper Creek?

 

[EdP]

Your calculated MV does seem low. My .280AI Cooper w/24" barrel gives 2900fps shooting 160gr Accubonds.

Hereinaz listed a bunch of factors that can become variables in calculating MV. You can get a decent chronograph for about $150 and get an accurate reading and not have to worry about those factors.