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! .



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).

Thank You for that and also for keeping the penetration measurements at tenths without an ending zero even if you show a tool with far greater capability at precision. Lol, I guess things and folks really are different Down Under!

Best regards,
shootski

Think the averaging of the two (expanded diameter/as shot diameter) should predict penetration close enough for comparison.

Does seem that airguns have "grown up", there is enough power on tap to trade some penetration for expansion when hunting traditional airgun game. So far, the predator is the best expanding design but i do hope that other makers give some serious thought to making more types available (and not just cheap knock-offs of the Predator).

...when you hit the squirrel....and pellet does not have to penetrate much more than 2" to kill them...

...come with precision calibrations! How else to explain wound channel depth accuracies of 3%?

Thanks for the - as usual for you - interesting and illuminating observations.

Steve

Glad I could post a good question. I need to do some of that testing myself.

Lee Brown, Chesapeake, VA

Catch a striped bass for me next time they run ....... Kind regards, Harry in OZ.

Season is out now. Sorry to get off topic.
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Lee Brown, Chesapeake, VA

still good eating I'll bet ... The Mods can dish it now ......... Kind regards and thanks again, Harry ( off to bed ).

I always enjoy your real world experiments with the Predator pellets. What is the expansion like with skull shots on critters the size of rabbits or squirrels? Have you done any tests with the .177 Predators? Please keep these experiments coming, look forward to them.

"You've come far, pilgrim."------"Feels like far."
"Were it worth the trouble?"----"Ah, what trouble?"

mainly because I have the rifles to do them justice.

In respect of head shots it seems to depend upon what the bone density is at the strike POI. I still have much to do but it seems a little counter-intuitive. Great expansion if the softer "spongy" bone is at POI. More dense "compact" bone seems to cause the pellets to be extruded and allows for deeper penetration on the far side like I found in this wood: About half an inch of wood has been split away to expose the pellets:

[IMG][/IMG]

The Predators penetrated deeper than the JSB Exacts and CMs and did not lose the red tip which seems to have been held by the surrounding lead compressing in upon it rather than expanding away as it does in softer tissue.

Still have field experiments to do in order to establish discrimination and consistency. These are a complex pellet easily dismissed at first glance but they grow on one as their characteristics are exposed.
I think the copy cats only emerged as shooters have found them to do most of what was claimed for them as a premier hunting pellet. ............ Kind regards, Harry.

that they would penetrate deeper in more dense bone than soft. One would think it would be the other way around. From your observations of the bone density penetration and the shots in wood, it would appear that the polymer tip is doing what it was designed to do by opening a wound channel for the pellet to enter. When I first saw them I was sure they were another gimmick pellet. After reading about them and trying them myself, I have definitely changed my mind about them! They are definitely a "food for thought" pellet.

As for the copy cat pellets, I see no need to try them myself. Not when the Predators are so consistently accurate and cause the amount of wound trauma they do.

Again, thanks for posting your experiments.

"You've come far, pilgrim."------"Feels like far."
"Were it worth the trouble?"----"Ah, what trouble?"

anything alive that I want dead...lol. I find the JSB exacts to shoot the same zero, so use them for plinking as they are less pricey...but I'll gladly pay for the preds for hunting. The Exacts are a tad better accuracy-wise for me past 50yds, but don't give up much more than 1/4 at 75.

They are absolutely deadly on everything I've shot thus far with them....the largest so far being a 22lb Possum at 34yds...placed between eye and ear from the side...the pred was very expanded and I found it under the hide on the off-side. It penetrated both sides of bone...which is quite impressive as Possum heads are notoriously robust.

I've shot 8 Armadillo's with them so far and probably 40 squirrels in the TechStar....after the first 3 were headshots and were through-and-through, I intentionally started taking body shots at different angles through the shell.....even longitudinally from the rear at a slightly downward angle, they penetrated into and through the vitals....

I shot probably 20 feral chickens in Hawaii with the B40, and found them far superior in penetrating the thick wing feathers of the big roosters, which again is an incredible feat....several times I had CP's fail to make lethal penetration through the wing butts out of the springer. The only thing I found that would effectively penetrate side-to-side on the roosters were 22.5gr Logun penetrators....but they tended to overpenetrate and keep whistling across the countryside...not good in a neighborhood...lol.

Keep the tests coming.....but for me, I'm completely convinced that there has never been a pellet to equal their lethality, and completely fail to see how anyone can improve on them....but 20 years ago, who would have thought we'd even be this far?

s/f

Jamie

that spot between the eye and the ear is where the thin "wings" of the bat-like Sphenoid bone come to the surface as the only protection in that area. It is indeed a deadly spot to aim for. The Predators would act in the manner they do in soft tissue there and expand perfectly. I hopr that Predator International will one day convince JSB to produce some .25 cal hulls for them to market a .25 cal Predator ....... Kind regards, Harry.