Help calculate muzzle velocity and drop

[svivian]

Talk about making something as complicated as possible

 

[35WhelenAI]

Fwiw, my Pro Chrono easily did arrows for archery, as well as any rifle.

Good question is it an archery only Chrono, but since he was gonna pull it out, I suspect it's not archery only. A whole lot of extra work and effort to figure out the answer to 2+2 when it was right there. Playing with drops is full of variables and the human element. That could've been taken out with a little bit of effort of pulling out the chronograph and getting the actual speeds of the bullet drops were being calculated with!

 

[sasquatch]

So your on the wrong track here, your math formula will never be accurate without chrono data. Everything we have given you is only estimates based on your group locations which isn't conclusive in one string of 3. There's so much off with how your trying to go about this I'm not certain I understand what your trying to accomplish?

If you just want to know how much drop your ammo has at different ranges then just use a tall target like you did. That's not going to be very practical past say 300yds though. If you know your MV then you can accurately do the math to get your drops at any range.

What kind of scope do you have? does it have external turrets to dial for drop?

What kind of chronograph do you have? is it only rated for archery? If not its accurate enough.

I think it’s a pro chrono that’s rated above archery. I THINK.

I bought it 15 years ago and haven’t touched it in 10. It’s buried in storage. Time will tell

The scope, trijicon tenmile.

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[Koda_]

I think it’s a pro chrono that’s rated above archery. I THINK.

I bought it 15 years ago and haven’t touched it in 10. It’s buried in storage. Time will tell

The scope, trijicon tenmile.

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Nice scope, Your pro chrono is just fine... dig that out, measure at least 10 rounds and average your velocity, enter that into a ballistic calculator then zero at 100yds and confirm your drops by shooting and your done.

 

[TaperPin]

I think you’re doing fine. Back before the average shooter had a chronograph it worked well to simply take your best guess based on the information you have, print out a dope chart and tape it on the stock. The more you shoot, the more it can be updated to be more accurate, and the chart reprinted. Shooting reliably out to 500 yards doesn't have to be complicated. In a lot of ways, shooting enough to develop your own chart is a better learning experience.

 

[EdP]

Has a chrono and didn't use it. Well don't that beat all.

At least I learned about firecracking.

 

[Hondo64d]

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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You can use your drops to determine velocity but everything else must be right. Your zero must be exact. BC, height over bore and air density numbers must all be good. Farther distances are better. I do mine at 800 yards or farther. Ballistic AE performs this function very well and only cost a few $. I have found when checking with a chronograph afterward that Ballistic AE’s velocity calculations are within a few fps of what the chrono says.

John

 

[Castle Rock]

I am firmly in the camp of the op
I will work off measured drops any day rather than rely on a cheap chrono
Physical testing beats theory any day

 

[EdP]

I am firmly in the camp of the op
I will work off measured drops any day rather than rely on a cheap chrono
Physical testing beats theory any day

I don't think in 30+ responses anyone on this thread has suggested relying on a chrono reading w/o testing, but rather that a chrono reading is the best place to begin your testing. A chrono reading entered into a ballistics program to predict drops and then testing to confirm seems like pretty standard practice. So does testing out to the max range you intend to shoot game if at all possible.

 

[35WhelenAI]

Chrono is a chrono, VERY rare they are off, and certainly not more than the human element. Pro chrono is not a "cheap" chrono, been tested for decades and is sound and reliable regardless of price.

Both and is the best combo, however the chrono would be 99% of what people with noses would choose to check drops that are not making "sense", IMO. Dig it out of storage, probably take less time than posting. Based on the first post, if you are going to use drops, then the velocity is lower than advertised, no other way to read it. Do what castlerock says and rely on that and save the time, or use a Chrono as proven data point.

I compared velocities with my Magnetospeed versus Prochrono. Magnetospeed runs about 10-15 FPS faster, which is what you lose in the first 15 feet out to the chrono.

 

[sasquatch]

Finally got to shoot. The ammo I was shooting when this thread was started (copper creek brand loaded with 162 eld-x) was 2600 fps across chrono. 100fps slower than the bullet drop math was indicating. And the box said it should be roughly 2950fps

I had some other ammo to shoot also incase it was to come in very slow.

Hornady 162 eld-x was coming in at 2840fps which is right there with what the box says

Nosler trophy grade 140gr accubond was coming in at 3050fps vs the box saying 3200

Nosler trophy grade 160 accubond was coming in at 2910 vs the box saying 2950

I had some Pendleton ammo loaded in the 162 gr eld-x also and it was coming in at 2850 but I’m not sure what the projected fps is of that ammo, still trying to dig it up.

For now I sighted it in for the Nosler 140s, while I order some more 140 and 160s to do some more shooting to see which it actually likes best.

I also have some hendershot ammo on order from weeks back but it’s not arrived yet.

One somewhat odd thing I seen, at 100 yards, just about all the ammo shot in the same 2” circle. However, the 140 grain Nosler was a big outlier shooting about 4” lower than all others, even though it’s faster.


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[35WhelenAI]

With handguns, the bullet leaves the barrel sooner (less barrel time) with lighter (and typically faster) bullets before the muzzle has risen as much vs a slower, heavier bullet with more barrel time. Not sure if the same principle applies with rifles to the same degree, but it is noticeable in handguns.

 

[sasquatch]

With handguns, the bullet leaves the barrel sooner (less barrel time) with lighter (and typically faster) bullets before the muzzle has risen as much vs a slower, heavier bullet with more barrel time. Not sure if the same principle applies with rifles to the same degree, but it is noticeable in handguns.

Interesting theory, it makes sense


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