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Discussion Starter #1
I like to look at a load's theoretical performance before I decide whether or not to use it. Can somebody tell me what the math is for Thorniley Stopping Power? I know that I can go to Beartooth's Ballistician's Corner and plug in the numbers, but I have very limited access to the net - just what the friendly gals here at the library will permit, about a half hour at a time.

DC
 

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DMC, I do not know the math for the Thorniley.
But the Taylor knok out value is a very good cartridge comparison formula.

bullet dia. X bullet weight X muzzle velocity / 7000 gns.
.458 x 465 X 2300 fps / 7000 =69.975

this is a way to compare different cartridges that you know will work, to compare against cartridges you want to see if they will work.

Hope this helps,
Halfbreed
 

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Discussion Starter #3
Thanks for the reply. I've played with the TKO and Lyman's OGW as well as Keith's LbFt. I think any of them give a truer picture than FPE. Was curious about Thorniley. It gives some weight to bullet diameter, but doesn't seem to give as much as Taylor's.

DC
 

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DMC said:
Thanks for the reply. I've played with the TKO and Lyman's OGW as well as Keith's LbFt. I think any of them give a truer picture than FPE. Was curious about Thorniley. It gives some weight to bullet diameter, but doesn't seem to give as much as Taylor's.

DC
Hi DMC,

I was cruising over the old posts and I saw your question. I am curious also as to what the Thorniley formula is. I have ran some numbers through it and the formula appears to be the following.

=2.866*velocity[fps]*(bullet weight[grains]/7000)*SquareRoot(bullet diameter[in])

The square root of the bullet diameter explains why the Thorniley stopping power value does not weigh diameter as heavily as the Taylor formula does.
 

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I have played with these formula for about fifty years now, first one and then the other. All are better that the standard ft/lbs/KE (which in itself is just a factor). Peter Thornily's has a lot going for it.
I give you another factor formula that I have developed, for you to play with, based on some things we have learned along the way. The others are based on a non-expanding bullet.....mine works both ways:
Maplat Area X Sectional Density X Velocity = Power Factor
Try it out!.........James
 

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James Gates said:
I have played with these formula for about fifty years now, first one and then the other. All are better that the standard ft/lbs/KE (which in itself is just a factor). Peter Thornily's has a lot going for it.
I give you another factor formula that I have developed, for you to play with, based on some things we have learned along the way. The others are based on a non-expanding bullet.....mine works both ways:
Maplat Area X Sectional Density X Velocity = Power Factor
Try it out!.........James
James,

Haven't tried your formula yet, but it's interesting. What about bullets that have a very small Maplat area, e.g. pointed bullets? Since you are including Maplat area in your formula, does this imply that you're a hard-cast guy?

Brian


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No, I am not just a cast bullet fan, but I do believe in Meplat Area, whether on an expanded jacketed bullet or non-expanded on hard cast. Note I include expanded MA.
Since I first started playing with a comparison factor, I realized that Sectional Density should replace Weight.
Sectional Density X Meplat Area x Velocity = Factor.
This factor formula takes into consideration the expanded MA where the others do not.
When you are playing with Peter Thornily formula, etc.....remember that are for non-expanding solids!
The only problem is recovering expanded jacked bullets to measure the MA.....but it can be done with a little work and water soaked paper situated at various ranges. Here we really see the diference in velocity and MA on jacketed bullets at various ranges.
I have never been satisfied that the ft/lbs of energy was a real yardstick for comparing Lethal Potential of various loads. At best it is a potential. Bullet design governs MA.
Regards, James
 

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A Thorniley Formula that matches the internet one

I'm pretty sure this one works.
TSP = G*V/10^5 (37*C + 100/9)
I've tried it on a large range of C=caliber in inches, G=bullet weight in grains,
and V=bullet velocity in feet per second.
 

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These calculations are nice, bur do not take into consideration the expansion of jacketed bullets.
Here's one that can be used to compare one bulet load to another!
Sectional Density x Meplat Area x Impact velocity.
 

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Discussion Starter #10
Daggone, somehow I lost track of this thread. First, a very belated thank you to mrb 1618. :eek:

Mr. Gates - again, as usual, more food for thought.

DC
 

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Something to consider.....Sectiomal Density (ergo penetration) is based, in its calculation, on the length of the bullet vs weight and caliber. A jacketed bullet loses SD as it expands and is shortened.
A non-expanding bullet with a large Meplat Area does not lose SD.
Regards, James
 

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Discussion Starter #12
An expanding bullet tosses in other variables:

How much does it expand? A bullet that expands to 2X its diameter winds up with a pretty anemic SD of 1/4 the SD of the same bullet that doesn't expand.

What medium will cause expansion? I have some bullets that are so stout that they will expand only in a very dense medium - flesh won't do it.

How much weight will the bullet shed on its trip? Jacket seperation, lead pieces breaking off, etc.

How quickly - at what depth - is expansion achieved?

Personally, I prefer a flat-nose, non-expanding bullet for almost all tasks.

DC
 

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I agree...with some reservation. I like the hard cast alloy bullet with a large Meplat Area for handguns and brush rifles between .357" and up.
In calibers below .357" .....such as my .30-06....I go with a jacketed bullet that has proven performance in game.
Just some thoughts....James
 
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