Well here is one example.
Further down the page (and frequently) the question of penetration prediction arose; see last cited reference.
Steve NC, following 19th Century brilliant mathematician Poncelet's musings, came up with the formula that penetration = impact velocity fps x weight gr / (53000 x pellet diameter^2).
Example: Real life field data, from an experiment some years back, showed that with an impact velocity of 770 fps a Predator .22 pellet of 16 gr penetrated a live rat lengthwise and stopped in a measured 3.5 inches (the rat then being dead
). The pellet had expanded to 0.315 inches in its travel in the rat from a rifle muzzle exit frontal diameter of 0.218"( this last established by pushing a pellet through the choked barrel).
If we apply Steve's maths we find the penetration of the fully expanded pellet would be 2.34 inches. Applying the maths to the same data but for a non expanded pellet gives 4.89 inches penetration.
If we assume that the expansion was at a consistent rate throughout its travel and average the two sets of data we find a penetration of 3.615 inches which is just a tad more than the actual measured 3.5 inches achieved in the rat. Now, if we further assume that the pellet expansion was more rapid in the early stages of its intra-rat travel (as I suspect to be the case), then my guess is that Steve NC's maths is VERY close to the money .... well at least for this expanding pellet / rat field example.
One never knows when "pure field research" will pop up for a semi useful end ahem!
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![[linked image]](http://img.photobucket.com/albums/v392/Kyogle/RatAug06.jpg)
The full field test graphics and data can be viewed here:
http://www.network54.com/Forum/79537/message/1154781644/Pellet+expansion-+Predator+21+fpe+dumped+in+a+rat+-+Graphic+pics%2C+no+kiddies+please
Extrapolation of this example to other pellets, impact velocities and results, would need to be examined on a case by case basis I suspect ........
But I couldn't help myself from testing the formula with the data that immediately sprang to mind when I read LEE in VA's post further down the page:
http://www.network54.com/Forum/79537/message/1246720130/Is+there+a+post+on+penetration-expansion+at+different+fpe-
Robert's response there is in small part given consideration in the included assumption of progressive expansion rate ( further qualified above ).
Any who have read this far .. hope you enjoyed the journey .... Kind regards, Yrrah Down Under (where things and folks ARE different).
