"Estimated Velocity"

S

steyrl

Guest
I have a "curiosity" question.

When your developing a load you usually have the maximum reccomended load and velocity but if you're starting 10% below is there anyway to estimate muzzle velocity?

I have a chrony and I know I can set it up and have the muzzle velocity read for me but I'm just curious to know if there IS a way of estimating veocities.

Best regards,
 
My chronograph seldom misrepresents, manipulates or fudges velocities as long as I take certain precautions I've learned. I'm not as sure about published performance where the publisher has a vested interest in the figures.

I'm happy to do some interpolation with powders, projectiles & barrels I'm familiar with once I've chronographed a reasonable sample, but mostly, I shoot over the screens. Apart from anything else, I can get a bigger picture of performance by shooting all my development loads over screens particularly when I'm working the final increments. Trends in spreads & SDs, an even consistency around sweet spots can become evident.
 
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It's A Guess, at Best

Here is why. When working with some of the small capacity cases, little things can produce big results.

Here is an example. Most loading manuals list loads by bullet weight. Very little is taken into consideration concerning bullet style, or actual size.

You can take a 6PPC and load a 66 grn Barts Ultra to a flat 3400 fps. You can then take the exact same everything, except substitute a Fowler,or similiar design 66 grn bullet, and gain darned near 100 fps. You would also be in the "danger" zone with pressure.

As the case capacity goes up, small things such as this have less affect. But it shows that you should never assume anything when it comesto working up loads with unfimiliar components........jackie
 
10%

If your starting at 10% under max and your going to work your way up wouldn't you want to use your chrono and know exactly where things are?
 
A chronograph measures velocity. The are all sorts of pressure signs that can be determined as you work a load up and none of them involve a chronograph. Every rifle may shoot the same load with a different velocity...
 
Thanks everyone for sharing your knowledge. I really appreciate it.
 
A chronograph can be used to determine excess pressure. Using load manuals subtract starting vel from maximum and get vel. per grain.Then as you shoot with increasing powder wt. watch for the vel. to change from being linear. If vel goes up greater or lessor than linear its time to back down.
 
Try my free reloaders spreadsheet

http://maxpages.com/thejedilair/Firearms_Shooting

or

example est

Powder mfg info

.223 Remington 55gr fmj
Say Hodgdon H4895 Powder 26grains Max 3315fps 49000 cup
Federal Brass CCI 400 Primers 24" mfg test barrel


Load is 23.7gr H4895

23.7/26=.9116 add .02=.9316 .9316*3315=3088fps 24" barrel

Est 25fps per inch of barrel

17.25" Mini 14 3088-168.75=~2919fps 24"mfg-17.25=6.75*25=168.75

26" 12FV 3088+50fps=~3138fps 26-24=2 2*25=50fps

.02 added to new pwdrchg grains/max pwdrghg grains is a correction factor
as seen in Lee Modern Reloading. Its an estimate good enough for me.
 
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