Bullet sectional density

[Dan]

The SD thing strikes me as an angels on the pinhead debate mostly. There is quote attributed to Yogi Berra that sums it up I think:

"In theory, there is no difference between theory and practice. But in practice, there is."


SD is relevant to external ballistics in context of BC calculation. Retained, or modified SD is the significant aspect of terminal ballistics. W.D.M. Bell understood that.

Theory says the higher SD is better for penetration. No argument from me on the theory. Practice says the theory is only relevant in inverse proportion to expansion. In other words, bullet construction/hardness/expansion are the metrics which count if penetration is the objective.

I don't really feel compelled to argue one side of the equation or the other, but report that the lowly .22 CB short does not expand much at all, regardless of what it strikes. It has a SD of about .08 if I did the math right, and retains that value with dogged determination.







I feel safe in discussing this because the short was originally a BP round.