Thornily Relative Stopping Power and the PRB

[ryoung14]

More playing with numbers on a cold and drizzly Saturday:

One of the forum members posted a link to this site:
[url] http://www.beartoothbullets.com/rescources/calculators/php/thornily.htm[/url]

I've been playing with the Thornily calculator and using roundball weights, diameters, and velocities to find the minimum velocity/load needed to take Whitetail at 100 yd. with a PRB. According to the site, a minimum Thornily score of '50' is needed to take cleanly take deer.

To reach this score with a:
.490 PRB of 177Gr.; a velocity >=970fps is needed
.530 PRB of 230Gr.; a velocity >=720fps is needed
.570 PRB of 276Gr.; a velocity >=560fps is needed

Checking the latest Lyman Black Powder Loading Manual (24" barrel) For:
.50 cal. 80Gr. of Goex 2f gives 970fps @ 100yd.
.54 cal. 40Gr.* of Goex 2f gives 865fps @ 100yd.
.58 cal. 60Gr.* of Goex 2f gives 898fps @ 100yd.
*Note: Lightest load listed in the Lyman manual for these calibers.

If these numbers can be believed, it appears that both the .54 and the .58 are MUCH more efficient harvesters of Whitetail than the .50 in terms of powder required. The .54 generates more than enough 'stopping power' using half the powder the .50 needs to make the magic score.

The point of this is to determine, if a light load is needed for accuracy, how light can a given caliber be loaded and still do the job?

Now before I subject some poor animal to actual pain and suffering in an attempt to verify these figures, would someone care to comment on the validity of this approach? Is a PRB load as light as 40gr. really a 100 yd deer killer in a .54? How about 60gr. in a .58? What are your experiences with light loads in these calibers?

I've read on other forums that the Thornily and Taylor formulas have been debunked. I've seen the Taylor formula 'debunked' (Taylor never meant for it to be applied this way) but not the Thornily. Can anyone point me to the discussion?

Thanks.
Bob

 

[Slamfire]

I ran the figures for the load I've the most experience with, a 140 grain 6.5mm bullet at a muzzle velocity of 2700 fps. The Thornly value give was 79. That means if I place the barrel agains the hide of a meat elk, and pull the trigger the elk will NOT die. I wonder what animals those 5 I shot with that load at a longer distance were, they looked, smelled, and tasted like elk. :blah:
The thing to remember is that an artist can create a bridge that will stand the test of time. An engineer will attempt to reduce the art to a mathematical formula. Sometimes this works, and sometimes it doesn't. :v

 

[ryoung14]

Yep, slam, it must be bunk. The .22RF isn't rated very high either, yet if I stuck one in a deer's ear and pulled the trigger, I bet he'd die.
Bob

 

[Wehrmacht]

Like the fellow said...." I don't understand all I know about this subject"....but I'm sure beyond any doubt that where the PRB hits the animal plays a very major role in what happens to the animal.I think we all have experiences that point this out. Right?

 

[pab1]

The numbers on the Thornily chart represent the minimum to cleanly harvest different species "under any condition's". I believe this is accounting for shots where a lot of penetration is required to reach the vitals. It is a useful reference tool that I often use. However I would not limit myself based solely on it.

If you run numbers for a .30-06, it hardly looks adequate for elk sized game. Tell that to the countless hunters who have taken elk with a .30-06 over the years. If you limit yourself to broadside shots through the vitals you should not have any problems.Shot placement is key. A knife through the heart will kill faster than 1,000 foot pounds in the last part of the animal to cross a fence.