A point to AussieGunWriter:
The "sectional density" figure, I'd like to state - is STILL a usefull one - and should NOT be relegated to the trash-heap of bullet discussions. Here's why.
People who dislike the term, point out, that is not really an accurate one - as it only applies to a non-deformed bullet. Scientifically speaking - that's correct. It's also true that bullet type, construction, weight and impact velocity can all affect a bullets ability to penetrate - but still, I think the sectional density figure is usefull. Here's when:
The average person doesn't have the ability to shoot thousands of game animals in the field to compare real world penetration abilities of bullets. The average person doesn't even have the time or location that will enable penetration tests using test media on all the bullets they wish to use.
The average guy has to rely on a printed number to make some determination as to which bullets are best for which circumstances. When comparing the same bullet's ability to penetrate an animal (or a test medium, for that matter) I think one can learn a lot by comparing the sectional density figures.
All things being equal - a bullet (of the same type) WILL penetrate futher if it has a higher sectional density figure than it will if it has a lower sectional density number.
Can you think of an exception? If you compared, for instance - a Nosler Partition or a Barnes TSX - can you think of an exception to the "higher sectional density figure providing greater penetration" rule? Can you think of an instance when a lighter bullet of the same caliber, launched at the same speed - will penetrate more (in the same substance) than it's heavier brethren? I know I can't.
It stands to reason that, as my Dad would have stated it - "the longer the stem on the mushroom - the deeper it'll go" - it has more "push" behind it.
Heavier bullets - of the same construction - penetrate deeper. This is what "Sectional Density" figures show. While not being totally "scientifically correct" - this figure is still a very usefull figure for the average person, to guesstimate the penetrating ability of a bullet - and as such - is a usefull concept to use.
I would personally speaking, even go further - and state that sectional density figures are useful when predicting penetrating abilities of the same types of bullets across different calibers - but that's a whole other debate. For another thread.
Just because something isn't actually scientificallly correct -doesn't render it useless, when it comes to understanding something in a generalized manner.
We hear about, and use "ballistic coefficient's" all the time -and see them listed as a number, so that we might compare a bullet's ability to fly flatter when having a higher ballistic coefficient than another bullet will fly if listed with a lower number.
Those figures too, are not "scientifically correct" as "ballistic coefficients" are not one number - but are, in fact, an endless and infinite series of numbers - that change as the wind resistance and declining speed of the projectile changes. But still, it's a usefull concept to use one "average" number to show a bullet's "ballistic coefficient". It's also a useful term for the average person, when trying to predict how one bullet will drop when compared to another. Scientifically accurate - or not.
It's the same with "sectional density" - it's still a good way for the average person to predict how similar constructed bullets will penetrate things. Scientifically accurate - or not.
More people, not less - should pay attention to those numbers.
They are usefull.
