Yes, I agree with you. The tumbling of the bullet made the difference.
Originally Posted by Ljutic
Based on this limited experience, I am also of the general opinion that the clear gel you are using seems to support a better match for the Schwartz bullet penetration model than the MacPherson model. I also really like that clear gel 'cause it lets you see everything. Very cool!
I don't know if you've read either book (Quantitative Ammunition Selection & Bullet Penetration), but I have found that the more complicated model found in Bullet Penetration consistently (IME) produces predictions that are less "in-line" with reality than what the Schwartz model does after evaluating them both over the last several months.
Even though the Schwartz model is derived of a much simpler equation of motion (that is, F=ma), it also has within its construction, the ability to consider differing material strengths in terms of an ultimate tensile strength (expressed in N/cm2) -found in Chapter 3 of Quantitative Ammunition Selection
(check out the second question on the FAQ page linked below)- Quantitative Ammunition Selection
The difference between the Schwartz model prediction of 18.92" and your test result of 18.5" is 0.42" (or 1.067cm) -just a smidge over the Schwartz model's 95% MOE of +/- 1.00 centimeter in matching your test results with a "stable" (non-tumbling) test bullet. Not bad...
The MacPherson bullet penetration model performed as it always seems to (at least for me) -by grossly over-estimating the penetration of the "stable" round by 1.61" (or 4.09cm). I suspect that this might have something to do with the Schwartz model's statistical population which is stated to be in excess of 700+ data whereas the MacPherson model relies on just 400+ data.
The more I compare these two models, the more I have found myself relying upon the Schwartz bullet penetration model for the most reliable answer.
The "icing on the cake", at least for me, is that it very easy to use. Yeah...I am lazy. :tongue: