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Discussion Starter #1
I keep seeing listings on ammo websites for grains, muzzle velocity, and energy in ft/lbs. Does anyone have the formula for this?

Tried searching, but couldn't find it. :dope:
 

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muddy math

"Grain" is a measurement of weight. 437.5 grains (normally written like this: "437.5g") equals one ounce.

"Velocity" is simply the measured launch speed of the bullet.

"Energy" is a calculation based on weight and speed that provide a comparison between loadings.
Most highly recommend not fixating on energy, as it relates little to actual demonstrated performance.

Any help?

(FWIW, if using a 45 ACP platform, suggest finding a modern 230g -see, there's that grain designator- JHP that functions with utter reliability from your gun. Winchester SXT, Remington Golden Saber, Hornady XTP, Federal Hydra-Shok, and Speer Gold Dot can all be tested.)
 

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Discussion Starter #3
Um, no, not really any help. ;)

I appreciate your post, and your desire to help, but you're reading too much into my question, and answering a question I'm not asking. I'm not searching for an ammo recommendation or a discussion about the importance of mass vs. velocity.

I'm pretty experienced, and I know what terms are in the formula, and I've been all around the debate on energy, shot placement, stopping power, etcetera. And I agree one should not focus on energy too much to the exclusion of other factors. I'm a 200-230 grain standard velocity .45 guy, too.

I'm just curious about the formula. I'm a geek that way. If I thought about it long enough, I could probably figure it out (especially with a little scotch to help). But I figure somebody around here has the formula handy.

I want the formula with conversion factors. How do I take grains and velocity, and end up with muzzle energy? I want the actual math, and I can't find it. I keep seeing this in articles on ammo and on the web sites, and I'm curious how one arrives at it, given projectile weight in grains, velocity in ft/s and ending up with ft/lbs.

Just looking for a math formula, not ammo recommendations. Thanks!
 

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Usable Handbook formulae

For years, I used the one in Speer #3 and everybody seemed to be on the same page with it. Rather than scientific notation It goes like Velocity x Velocity x bullet weight in grains / 450240. Looking at the various ballistic tables, it worked out just fine

The Speer # 14 Now says Velocity x velocity x bullet weight in grains/ 450400. I had seen that on line a few times and assumed that it was wrong but now speer is using it. Here's how it would work out with a moderate .44 working load:

1000 x 1000 x 250 /450240=555.259 ft/lbs

and the new conversion constant:
1000 x 1000 x 250 /450400=555.082 ft/lbs.

So, I guess either would be correct.
 

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E=1/2 mv2

Kinetic energy equals one half mass X velocity squared.

Mass is not weight. To get mass from grains, you divide the weight
in grains by 7000, as there are 7000 grains in a pound. Then divide
by the gravitational constant -- here's where the variability is probably
coming from. A constant of 32.2 is often used. Some use 32.174, calling
it 'standard gravity.' I do not know what it is for a fact.

To calculate E for a specific example, you would have the bullet weight
in grains times the velocity squared, divided by 2 times 7000 times 32.174.
2 times 7000 times 32.174 = 450436.

Using different gravitational constants will give you different formulae.
Which is correct? I don't know. If you look at MEC's example, it doesn't
matter much.


Joe
 

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Just to be prepared to discuss the topic one first needs to read:

"Gunshot Injuries" - Louis Lagarde (Chief Surgeon U.S. Army)
"Gunshot Wounds" - Dr. Vincent Di Maio
"Hatcher's Textbook of Pistol & Revolvers" - Gen. Julian S. Hatcher
"Bullet Penetration, Modeling the tynamics and incapacitation resulting from Wound Trauma" - Duncan MacPherson
"Stopping Power" Vol.s 1-3 - Evan Marshall
"Cooper on Handguns" (1974) - Jeff Cooper

You dont have to agree with any of these (and you will note that often the above have areas of disagreement) but they give you the basics.

There is much more out there worthwhile, but these are the bare minimum.

Jim H.

There is a good treatment of the topic in general in "The Perfect Shot - Africa" by Roberts (not the same as the American version by Boddington) but it is primarily about rifles on big game.
 
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