Sectional density question

Amon458 · Feb 27, 2015

Does sectional denisty matter as much on all brass or copper bullets or even steel jacketed bullets like hornady's dgs?

lcq · Feb 27, 2015

Lots of booze has been consumed around the fire discussing this.

Sectional density is the ratio of an object's mass to its cross-sectional area. It conveys how well an object's mass is distributed (by its shape) to overcome resistance.

To my understanding (I could be wrong) in pure theoretical terms this only applies to solids as once the projectile opens and how soon and large it opens throws sectional density out the window. Further monometals and bonded bullets hold together and don't fragment or lose mass and tend to penetrate deeper.

my $0.02

35bore · Feb 27, 2015

Lots of booze.!.!

I have not researched the topic much myself ,but I think lcq is right, being the two or three article's I did read all pertained and we're limited to solids.

Guessing the time I will do more research on this topic will be when I hunt a critter that could eat, stomp, or gore me. Interested to hear comments from those whom have hunted these critters, just to see if it matters much once you get above the 458 diameter.

jeffpg · Feb 27, 2015

For me it's best said in simple layman's terms as "all things being equal" the greater the SD, the better the penetration.

lcq · Feb 27, 2015

jeffpg said:
For me it's best said in simple layman's terms as "all things being equal" the greater the SD, the better the penetration.

exactly the key phrase "all things being equal"

Scott Slough · Feb 27, 2015

jeffpg said:
For me it's best said in simple layman's terms as "all things being equal" the greater the SD, the better the penetration.

If we could just get the world to cooperate and keep "all things equal"

!

stug · Feb 27, 2015

Karamojo Bell's requirement was a solid projectile 4 calibres long, ie a .284 calibre projectile needs to be 1.136" long.

colorado · Feb 28, 2015

For dangerous game I like all of my expanding bullets, monometal or bonded to have a sectional density of over 3.0 For elk, deer, etc. it's much less important. Our favorite bullet in our 270 Winchesters for deer and elk is the 150g Nosler Partition moving at least 2900 fps. In a pinch, I'd use that for grizzly as well.

Curious · Mar 11, 2015

stug said:
Karamojo Bell's requirement was a solid projectile 4 calibres long, ie a .284 calibre projectile needs to be 1.136" long.

...and Bell wrote "no soft-point ever touched this gun!"

matt85 · Mar 14, 2015

with solids, SD is very important. with soft points its less important but still has a place. its true when a bullet expands the SD changes but a bullet that starts with a better SD then its counterpart will likely still have a better SD then its counter part after they both expand. bullets with better SD are more likely to penetrate solid objects like bone. also a bullet with a high SD tends to be heavy for caliber which means it also has more mass to carry its energy after expanding.

-matt

postoak · Mar 15, 2015

With bullets of the same mass, sectional density is just the equivalent of the length of a bullet. So, a .22 caliber bullet and a .45 caliber bullet of the same composition with the same sectional density and in the shape of a perfect cylinder will be the same length, even though they will look vastly different in terms of length to width ratio. And two bullets with the same length to width ratio in these calibers will have vastly different sectional densities.

I think the answer to your question is "yes". If you had two bullets of vastly different mass due to composition, and they had the same external profile, the one of the less dense metal, and hence, lower sectional density would penetrate less, given identical bullet expansion.

Sectional density question

Amon458

lcq

35bore

jeffpg

lcq

Scott Slough

stug

colorado

Curious

matt85

postoak

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