Calculating muzzle velocity from published min and max loads

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ericrose

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Is there a formula that can be applied to determine the theoretical MV of a round that is loaded somewhere between min and max published load data?

When looking at the Hodgdon's website it only gives a starting load and a max load. The load I have found that works best in somewhere in the upper middle.

Yes I know the only way to find out the true MV is to use something like a chronograph and I will do that at some point but I want something that gives me some quick data.

Would also be useful to be able to load in a specific MV you want and have it spit out the load you should use in grn's.

Thanks,

Eric
 
Zero your rifle at 100y, build a tall target and measure bullet drop at 400+ yards. Tweak velocity in JBM Ballistics to jive with your real world results
 
What you want may or may not be possible. References vary from 30 to 50 fps to allow for inch of barrel difference from published data. So not really reasonable to have some computer or math thing tell you how fast your muzzle velocity is - more or less has to be by a chronograph??
 
Never looked at it but wouldn't Quickload do that?

In the real world there's a ton of variables that will have an effect and can't really be accounted for easily.

For very rough estimates you could use the numbers you have to get a ratio and use for your load. Pressure curves etc, aren't a linear relationship so that won't be very accurate.
 
The load manual will show, say 2460 low to 2900 high.

I own multiple rifles in some calibers. Even with the same barrel length in rifles chambered with the same reamer, I see a 150 fps variation with the same load. Throw in tighter bores, shorter throats, etc. and the variations can be greater. Then if the book rifle is 26" and yours is 20 or 22". it will be slower.

It would not be unusual for your rifle to be 200 fps slower than the rifle in the book.

To answer your question, your velocity will probably be between the hi and the lo. A closer number is not predictbale.
 
I looked at Quickload and it seems clunky to me. Also the coding is VERY out of date and they seem to only supply the program on disks. Who does that anymore?! Most computers don't even have optical drives anymore.
 
Quickload will give a velocity depending on the weight of powder, yes. How accurate that would be, who knows. It is clunky. I don't know of anything else that would do that though.
 
Use a chrono and be done with it. There is too many variables ..barrel length - conditions - no two barrel is exactly the same - bullet lots - powder lot - outside air temp - altitude ect to be usefull data. The only real data is the one taken from your gun - with your components on actual firing conditions.
 
Quickload will only give you an estimate. Changes in burn rate, case capacity, seating depth, and barrels make a substantial difference.

Only real way is buy a chrono. An approximate could be produced using a tall target but the variables are fairly large.
 
ericrose said:
I looked at Quickload and it seems clunky to me. Also the coding is VERY out of date and they seem to only supply the program on disks. Who does that anymore?! Most computers don't even have optical drives anymore.
Click to expand...
I think Q.L. was developed when DOS 3.1 was modern, lol!
 
The Data in the book,Hudgens,etc ,is close ,at best.
My hornady manual states that my 7 Rem should be pushing my bullit at 3000 fps, but my chronograph says 3150 fps.
 
No, I do not think you can calculate smth like that using a math relationship.
The muzzle velocity depends on some unique gun and environmental parameters such as casing dimensions, chamber dimensions, throat length, barrel length, barrel quality (lapped or not), temperature.... on top of that should be added that listed book velocities are a bit "optimistic"
 
Chrony, or measure bullet drop difference between 100 and something much farther.
Simple most accurate way is the chrony.
With a chrony and Strelok, I've had no problems dialing in a 100 yard zero to 1000m and getting on target with the first round. Without a chrony you just have no idea of muzzle velocity.
 
haha crossing this boat now with that 7 rem mag of mine now ive shot it to 500m, interesting.

Say my ZERO ? or POI is +2 inch at 100m , and i know its 300-400-500 , how do i set JBM calc to have that Factor included? Zero height? or Zero OFfset?

EDIT_ i worked it out, but most things line up except say the 300m,,,,,,, is that jbm the be all end all or could things vary? or have i shot confirmed wrong.
 
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This online program does what I am looking for but unfortunately has a very limit selection of powders. So the math is out there, just need to find the appropriate inputs.

http://www.bbt.scot/ballistics/pressure.htm

Also on the JBM there are several programs listed plus you can download the program code and play with it yourself. It's in BASIC so not all that hard to understand.
 
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