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Old November 5th, 2008, 02:38   #54
DonP's Avatar
Join Date: Jul 2002
Location: Edmonton, AB
Originally Posted by MadMax View Post
-varying thickness in putty target
Hmm, that's true. While my putty thickness was pretty even (used a roller and measured the first few, I didn't measure each and every one.

It's possible --- unlikely I think (but of course I would think that since it would go against my hypothesis) but possible that some of the BB impact areas were markedly thicker than others. But so much that it would throw off the observed trend? Maybe.

It seems that your putty pad isn't very thick. Thin pads bring the backstop into play when the putty deforms and backs into the rigid backstop. I would think that a very thick pad of putty (say 2") would reduce the effect of varying thickness to the backstop by taking the backstop out of the deformation behavior altogether.
I did notice some BBs hits deforming the back of the putty pad (see the APS2 result for the .12g - it deformed the back even though it actually didn't penetrate that far.) This does affect the "toughness" of the putty, but I figured that the effect should be consistent across all the BB hits, and should all cancel out, no? Again, I'm probably just happily declaring immaterial something that would otherwise require me to set the test back up and challenge my assumptions. Screw that.

Most putties tend to be non Newtonian.
Hmm, this is a really good point I hadn't considered. Maybe ballistic gelatin would be better. But much messier and harder to set up, so therefore surely it wouldn't be worth trying!

I think it is also important to also measure the muzzle velocity just before the pellet impact. Making an assumption of constant energy may be a mistake when you're trying to correlate performance with damage potential.
Do you mean measure the muzzle velocity between different shots of the same BB weight to make sure I'm not getting the odd "hot shot" or something?

I don't see velocity being relevant otherwise, unless I'm missing your meaning.

EDIT: Oh, I think I get it. Repeating the tests at 6" might be interesting just to see if (and how much) .12g penetrates more at 6" as opposed to 2m. If there is a condition where lighter ammo possibly gets MORE penetration, I guess it would be right at the muzzle or never.

Last edited by DonP; November 5th, 2008 at 02:52..
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