Calculating muzzle velocity from published min and max loads

I am curious if you get software to work for you. Recently read my first ever Sierra Manual - I suspect they know something about bullets? I note that they list three different Ballistic Co-Efficients (B.C.) for their bullets - three different speed ranges, so even that "number" is not a fixed value for a specific bullet - generally has higher value at slower speeds, and lower value at higher speeds. I suspect for longer range stuff, any bullet will pass through all three velocity zones, so becomes a real challenge, if the software asks for "one" B.C. input value. And very common experience that actual muzzle velocity, as measured (not calculated), borders on "unpredictable" - within say 150 fps range - one rifle to another...
 
For what you want, just assume that MV's are linear for increasing charge weights (they are not), and assume that what Hodgdon states will apply to your rifle (it will not) and you'll have an estimate that's roughly +/- 20%.
 
In the Lee Modern Reloading manual, there are 2 columns on the rightmost side of the loading tables
One of them is 1 grain veloc. This one (when available) shows the velocity reduction by reducing the powder charge by 1 grain.
Given the max load and velocity listed, you can compute your velocity using this factor.
This would be dead on if you're using Lee's test barrel.

Otherwise, if you measure the velocity for a charge, you may get a good computation at a different charge.
 
If you just want a theoretical number:

Example data:
min load 55gr 2500fps
Max load 60 gr. 3000fps

Formula: (max velocity - start velocity) / (Max load - start load) = fps gain per grain
=(3000-2500)/(60-55)
=500/5
=100 fps per grain in the min-max range. If you wanted to know the velocity at 57gr then: 2gr = 200 fps increase over start velocity, or 2700fps

Completely unreliable but qualifies as theoretical.
 
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I often wonder with these BDC bluetooth Wifi Rangrfinding Aimers ? or even any sort of App ? that there has to be a fair degree of error.
someone mentiones the above is a %20 guestimate..... an i rekon the Apps are like %10 or so, do ya rekon?

i pick up that every gun is so different in whatever way, an i find it hard that a computor can automatically put out the ultimate charge for that rifle an load?

or it may well be way over my head and ill go home now lol
 
I don't think you're going to have much success, I've found that a reloading manual is rarely within 60-80 fps of the velocities I've actually gotten.
I use a chronograph, then feed the numbers from that into one of the ballistics apps. Lapua is the one I'm using now.
That'll give you a good starting point, but you may find that you need to adjust your velocity input to get accurate results from any app.
As an example, I noticed over time that the suggestions from the app were putting me slightly high at each distance.
I increased my velocity input by 40 fps, now it's pretty much spot on at each distance that I shoot.
My conclusion was that the chronograph reads about 40 fps slower than my actual bullet speed in the 2800-2900 fps range.
That's been proven true for a couple of different rifles over the past year or so.

Before chronographs were both available and affordable, that's how shooters got their drops for various ranges. Shooting and recording results, then tweaking the numbers over time.
 
Potashminer said:
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??
Click to expand...

The bullet drop between distances should be a constant, integral with velocity. Barrel length may effect velocity but it won't effect the bullet drop at that particular velocity.

Back in the day, when very few people had access to chronographs, the only practical method of deducing the appx velocity of a load was to shoot to point of aim at 100 yards, then shoot to point of aim at 300-400 yards and measure the bullet drop.

Many manuals actually have drop rate charts for different velocities with bullets of given weights/diameters. Hornady and Speer used to have them, but discontinued them. The older Hornady manuals, including the fourth edition which actually had two manuals, one for load tables and one for velocity charts were excellent.

I believe those charts are available online.

When you start measuring bullet drop past 300 yards, bullet design, such as ELD or VLD starts to become a factor.

Simply measuring the bullet drop between a one hundred yard zero and a 300 yard point of aim, then comparing it to the proper chart will give you surpisingly close velocities. I've checked these charts against chronographs and magnetospeed units and the difference isn't enough to make any difference in the real world.

One shot at each range is OK but three shot groups are better for deducing drops and eliminates sighting errors.
 
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Chilly807 said:
I don't think you're going to have much success,

Before chronographs were both available and affordable, that's how shooters got their drops for various ranges. Shooting and recording results, then tweaking the numbers over time.
Click to expand...

Thats intersting and i like old school, so im going to skip the technology bit and just shoot and record. adjust. shoot.

Some guys seem to really bang on about stuff like quick load and other apps- but i wonder if they dont get out too much either, an the odd occaisons it lines up and everything is hunky dorey....
i guess some situations (not heaps) may call for this degree of 'information' and 'confusion' all in the same go :D

k.i.s .s :)
 
Andy said:
For what you want, just assume that MV's are linear for increasing charge weights (they are not), and assume that what Hodgdon states will apply to your rifle (it will not) and you'll have an estimate that's roughly +/- 20%.
Click to expand...

'close enough to hit dirt'.... then adjust for a hit.. repeat at 3 to 4 other distances.... reverse calculated your BC and velocity with all 'system' errors accounted for.

Confirm at a few more distances and....

enjoy...

Jerry
 
jethunter said:
If you just want a theoretical number:

Example data:
min load 55gr 2500fps
Max load 60 gr. 3000fps

Formula: (start velocity-max velocity)/ Max load - start load) = fps per grain
=(3000-2500)/(60-55)
=500/5
=100 fps per grain in the min-max range. If you wanted to know the velocity at 57gr then: 2gr = 200 fps increase over start velocity, or 2700fps

Completely unreliable but qualifies as theoretical.
Click to expand...

i did somethin different for long time til just the other day when i seenthis post,

the manual has the min max, Divide the FPS by the GR of powder an get a number, the more powder so using your 223 example of 55gr for 2500 = 45.4 whereas 60gr for 3000 = 50

so for 57GR i would guestimate around 47 x 57gr = 2670 fps.... give or take from the TEST barrel the figures come about from. :) which internet says about 25-50fps per inch. ymmv
 
Didn't read all the posts except but here is how I do it
Load data: H4895
Sierra #1365 55g FMJ
Starting load 23.1 velocity 2800 fps
Max load 26.1 velocity 3300 fps
30 grains difference between min/max is 500 fps therefore each grain would be roughly 16.6 feet per0.1 therefore I would expect a load of 25.2 grains would be approximately 3148 fps if all things are equal (neck tension / scale accuracy / experience)

this load data was from The complete reloading manual for the .223 remington page 35
 
IvoB said:
Didn't read all the posts except but here is how I do it
Load data: H4895
Sierra #1365 55g FMJ
Starting load 23.1 velocity 2800 fps
Max load 26.1 velocity 3300 fps
30 grains difference between min/max is 500 fps therefore each grain would be roughly 16.6 feet per0.1 therefore I would expect a load of 25.2 grains would be approximately 3148 fps if all things are equal (neck tension / scale accuracy / experience)

this load data was from The complete reloading manual for the .223 remington page 35
Click to expand...

A theoretical approach that will not hold up in real life.
As you add powder, you increase pressure and temperature, which increases burn rate. The pressure increase is not linear.
 
WhelanLad said:
Thats intersting and i like old school, so im going to skip the technology bit and just shoot and record. adjust. shoot.

Some guys seem to really bang on about stuff like quick load and other apps- but i wonder if they dont get out too much either, an the odd occaisons it lines up and everything is hunky dorey....
i guess some situations (not heaps) may call for this degree of 'information' and 'confusion' all in the same go :D

k.i.s .s :)
Click to expand...
This is the way.

PBOP is the only calculator that is never wrong if the technician is competent. Put Bullets On Paper.

Tables, online calculators, and forum experts are good for getting a starting point, but to "know", you need to shoot.
 
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