Penetration 270 vs 30/06

[Ray B]

The sectional density is a measure of the average length of the bullet. It isn't the actual length because instead of being a barrel shaped cylinder bullets are pointed, The penetration of a bullet will be the result of the force pushing the bullet, the toughness of the media through which the bullet is traveling, and in effect, the ballistic coefficient, or amount of traction the bullet has against the media. I know I lost a few with the term ballistic coefficient because some are so tied to the term regarding the bullet shape prior to impact. But The aspects of bullet shape as it travels through media has a very significant effect on how far it travels. A pointed FMJ that distorts little on impact ill tend to slice its way through and will have very little traction on the media- so it will travel a great distance but will have little effect on disrupting media. An expanding bullet that on impact distorts into something of a mushroom shape, larger frontal surface area, flatter, perpendicular to the direction of travel will have more traction on the media and will need to push the media out of its way as it penetrates. As such the penetration will be less, but the effect on the media will be much more.
To answer your question: it's an equation- the .30 has more weight which is more force potential, but it also has more frontal area so has less penetration potential. The .27 has the opposites. Since they have characteristics that are somewhat a wash, the actual penetration will be a result of which bullet has the least resistance in it's particular flight path.

 

[colorado]

A 150g A-Frame in a 270 Win at 2900 fps, or a 180g A-Frame from a 30-06 will kill anything you want in North America (can't say about Africa because I've never been there), except you might want to go with a bigger caliber for brown bear

 

[rookhawk]

Lots of mixed metaphors in this thread.

First reminder, copper bullets are very light for their volume, roughly 22% lighter than lead.

So in light of that, when you say 130gr Barnes its the same as saying 150gr lead. That's about as big of a bullet as you'll stabilize in a 270 barrel with normal twist rates. Same when you say 30-06 150gr copper barnes, that's volumetrically a 180gr bullet. Expansion of the barnes and their volumetric equivalent in lead is about the same size hole.

A better sectional density generally penetrates deeper. On the other hand, the heavier mass of the lead will have more momentum in all likelihood. That's why the math is so hard to model for the comparison.

The one advantage of the 270 with a 130gr barnes is you're getting a bit of a bonus. You're getting a huge bullet by volume coming out of a 270 relatively speaking, but its light so you're getting more velocity than a 150gr out of a 30-06. You may get more hydrostatic shock out of the deal at close range.

My son shoots 140gr barnes bullets from his 7mm and they make an awful mess of medium sized creatures, I suspect the 130gr barnes from a 270 might be a similar situation. Not your friend if meat damage is something you want to avoid. Penetration was to the skin on the backside for oryx and through the heart but no further on eland.