Accidental kinetic energy experiment


August 7, 2007, 01:33 PM
My son and I were shooting at 2” clay targets (Daisy “shatterblast”, or low-calorie Necco wafers) recently. He was using a $20 Daisy BB rifle and I was using a somewhat higher quality Marksman pellet rifle. I can take starlings at 25yd with ease, but was having a heckuva time hitting the clay targets. Meanwhile, my son (11) was busting a target with every 2nd shot, inspite of a crappy, mis-aligned sight on the Daisy. “Here, Dad, let me finish that up for ya”. Embarassing. Finally noticed the larger fragments had holes in them that had not shattered the clay. Hmmm... Took a few shots at a fresh target, them examined it. I was hitting nearly every time, but the pellets penetrated without shattering the target.

Using manufacturer data, the pellet rifle has twice the muzzel velocity of the BB gun, and the lead pellets are 1.5 times as heavy as the steel BBs. Overall, I'm hitting the target with 6 times the kinetic energy, with less overall effect on the target. Kinda weird.


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August 7, 2007, 01:35 PM
EDIT: Reread, let me change what I think :p

My thought is that a BB may not be able to zip straight through the clay, but instead transfers all off its energy directly into it. The pellet is capable of "cutting" through, keeping the damage to a small area, while retaining energy.

August 7, 2007, 01:39 PM
It's energy RECEIVED or ABSORBED, not energy DELIVERED that matters. The higher-speed pellets, despite a greater ballistic cross-section, were shattering the target structure directly ahead of the pellets' path. The slower-moving BBs were effectively delivering greater shock, which was spread over more of the target, thus propagating cracks and failure of the overall target structure.


August 7, 2007, 01:46 PM
There's other things you need to consider:

Smaller projectiles will often penetrate further than larger projectiles. Think of a knife through steak versus your fist through steak. You can cut through the steak very easily with the knife, but punching it really hard won't necessarily be enough to penetrate (depends on the particular steak :) )

The material's strength will affect things, too. Softer materials will deform. This deformation, and subsequent change of shape, can cause either a greater or lesser transferral of energy into the target.

The elasticity of the materials. A more elastic material hitting a harder target could absorb much of the energy (of course, this is related to deformation, above).

And, I'm sure there's plenty of other considerations to terminal ballistics :)

August 7, 2007, 02:12 PM
Ya know this is going to degenerate into a 9mm vs. .45ACP debate...yet again.:evil: Big and slow vs. small and fast...Sheesh!:rolleyes:

What air rifle round for zombies? .177 or .22 or .25? Pellets or BB's? Pneumatic or CO2? Oh boy!


August 7, 2007, 02:43 PM

*laugh* Yeah, I can see that happening. I was actually picturing more .22 vs .50, though (of course, I don't know typical muzzle velocities of these two calibers, and would rather state my ignorance than do what would probably be a two second google search).

August 7, 2007, 02:51 PM
Dont tell him till hes older, Im shure that gave him great confidence!

August 7, 2007, 04:55 PM
This reminds me of the time my buddy and I were shooting pop bottles out in my back yard. (Yes, we cleaned up the debris afterward... otherwise I wouldn't have been able to sit for a while!) I was shooting a CO2 pellet gun, and he was shooting a pump BB gun. The lead pellets would bounce off the bottles with a happy little ting noise, while the BBs would put holes in the bottles. We couldn't figure out how a fully-charged CO2 rifle firing faster, heavier pellets had less effect on the bottles until I fired a shot straight down the mouth of the bottle, causing the whole bottom of the bottle to shatter...

August 7, 2007, 05:04 PM
This is, in a general sense, a case of overpenetration. Your round was carrying through and delivering almost no energy to the target.


August 7, 2007, 05:06 PM
As a long time sporting clays shooter shooter, I've seen many clays laying on the ground with 1 or 2 neat round holes though them but otherwise intact and, no doubt, scored as a lost bird. I've seen rabbit targets with their thick rims take multiple hits of #8 shot and fail to break. It kinda disproves the golden bb theory.

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