I am sure this is a rehash, but it really got me thinking, comparing a 7mm to a .308 caliber. The typical comparison is 140's of the 7mm, verses 150's of the .308 and 160's of 7mm verses 180's in .308. Think about this but not too hard. With the extra velocity from the lighter round in the 7mm's, "if" the 7mm's have just .024" more expansion, due to the higher impact velocity, have you not lost the magical s.d. advantage, due to the equal wound channel, with less mass thus bleeding off the energy faster with less penetration ? If this is the case, would not be the expansion rate of said bullet be much more important than the magic sectional density. If you can't tell, unless you are hunting the big stuff in Africa, I think mass X speed= energy has far more value than that extra .024" This would in my mind be why deer are just as worried about a .30-06 as they are a .280!

quote:

Originally posted by Moorepower:
I am sure this is a rehash, but it really got me thinking, comparing a 7mm to a .308 caliber. The typical comparison is 140's of the 7mm, verses 150's of the .308 and 160's of 7mm verses 180's in .308. Think about this but not too hard. With the extra velocity from the lighter round in the 7mm's, "if" the 7mm's have just .024" more expansion, due to the higher impact velocity, have you not lost the magical s.d. advantage, due to the equal wound channel, with less mass thus bleeding off the energy faster with less penetration ? If this is the case, would not be the expansion rate of said bullet be much more important than the magic sectional density. If you can't tell, unless you are hunting the big stuff in Africa, I think mass X speed= energy has far more value than that extra .024" This would in my mind be why deer are just as worried about a .30-06 as they are a .280!

quote:

Originally posted by Moorepower:
I am sure this is a rehash, but it really got me thinking, comparing a 7mm to a .308 caliber. The typical comparison is 140's of the 7mm, verses 150's of the .308 and 160's of 7mm verses 180's in .308. Think about this but not too hard. With the extra velocity from the lighter round in the 7mm's, "if" the 7mm's have just .024" more expansion, due to the higher impact velocity, have you not lost the magical s.d. advantage, due to the equal wound channel, with less mass thus bleeding off the energy faster with less penetration ? If this is the case, would not be the expansion rate of said bullet be much more important than the magic sectional density. If you can't tell, unless you are hunting the big stuff in Africa, I think mass X speed= energy has far more value than that extra .024" This would in my mind be why deer are just as worried about a .30-06 as they are a .280!

When you get that figured out regarding the relevance of it all to your applied hunting practices, use that knowledge and compare similar and dissimilar bullet types per caliber.

Enjoy the ride and don't forget about shot placement.

Wow… smaller caliber/bullet weight vis-à-vis bigger caliber/bullet weight…expansion vis-à-vis sectional density… energy transfer of bullet weight vis-à-vis expansion to/into the hunted game… Oh yeah this is definitely a Jack O’Conner vs. Elmer Keith argument if I’ve ever seen one!

Plain and simple, a properly constructed expanding bullet that penetrates into and does damage to the vital internals of the game being hunted so that the game animal (in the widest sense of the word) quickly succumbs from the bullet damage is all that is required. This is a tricky balance whether the bullet be CnC (traditional cup and core), bonded, or monometal.

From that point forward the minimum caliber to be used is often dictated by the game hunting laws and regulations of the jurisdiction, state, or country in which the hunt will take place. Some hunters desire to use the minimum caliber dictated by these laws or regulations, others like to use something larger.

SD is not something important. The bullet is going to do 1 of the following:

- Miss the animal
- Stop at the shoulder bone
- Stop at far side hide
- Exit

Shooting modern TSX, exit is very happen.

Good idea to focus on frontal area and ballistic coefficient. Unless bored

One can get lost in the infinitesimal nuances between 308 bullets and 7mm bullets. Truthfully, there isn't much difference between them. Sectional density and velocity show up more when comparing 25 caliber to 30 caliber to 338 caliber bullets.

If it were my decision, if I were to shoot deer and smaller game, I would pick the 7mm-08. If I were to shoot deer and larger, I would pick the .308.

Sectional density is a good predictor of penetration, but I wouldn't get hung up on it, unless shooting dangerous game, then the rule of thumb is choose a bullet with a SD over .300. In the smaller calibers, a good BC is often something more to fret about.

John

I don't think deer are worried about any of this stuff.....

When smokeless powder came on, bullets were all simple "cup and core" designs and Sectional Density was developed to give us a rough idea of what could be expected for penatration.

With today's vast array of advanced bullets, S.D. is meaningless for predicting anything at all.

SOme have argued that the bullets SD changes as it expands. So a bullet like the NP or TSX that maintains it's bearing length will penetrate deeper than a bullet w/ shorter bearing length/shank. Think a std. cup/core 160gr/7mm & a 160grTSX, the TSX is likely to penetrate much further even though SD is the same starting out. Makes sense to me. So regardless of the frontal area, if the supporting shank is long enough, you'll get straighter, deeper penetration.