Understanding bullet energy: 308 vs 30-30

[gumbl3]

squaring makes a huge difference.. Remember what x^2 looked like on a graph in algebra..

[trophy8]

Speed kills. And sectional density.

[JW]

Speed kills. And sectional density.

Testify.


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[Black Ice]

308
150 gr
18" barrel
~2600 fps

30-30
150 gr
20" barrel
~2390 fps

Why does a 308 have so much more energy per the ballistic charts? Is it all ballistic coefficient? Both are 150 gr and going similar speeds

I'm just curious why you chose a .308 in 18" barrel and a longer barrel for the 30/30. Excluding AR's most .308's in a standard hunting rifle will have a 22" barrel which will probably move that 150 gr bullet closer to 2790 which is 400 fps faster. Also the .308 is probably better off shooting a 160 to 165 gr bullet which would come in around 2650.


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[GrapeApe]

Drive 70 and stick your hand out the window. Put it flat against the wind, that's the 30-30. Turn it so your palm is flat with the ground, that's the .308.

[TxAg]

I'm just curious why you chose a .308 in 18" barrel and a longer barrel for the 30/30. Excluding AR's most .308's in a standard hunting rifle will have a 22" barrel which will probably move that 150 gr bullet closer to 2790 which is 400 fps faster. Also the .308 is probably better off shooting a 160 to 165 gr bullet which would come in around 2650.


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Picking the numbers I did narrows the gap between the two which makes the answer to my question more relevant.

[LWD]

It's the exponent. Squaring the velocity makes all the difference in the numbers. But does it make that much difference in the killing? I like velocity because I'm mostly hunting with Barnes bullets, and I want the velocity to open them at longer ranges. But I don't subscribe to minimum energy numbers. I think in terms of a bullet going fast enough to expand to do sufficient tissue damage if place correctly.

Dangerous game hunters pay little attention to energy numbers. Momentum—mass x velocity—is a much more meaningful number. The momentum of the bullet, which factors equally velocity and mass, tells you much more about the bullet's penetration. There's a reason you shoot a cape buffalo with a .416 and not a .300 magnum.

LWD

[Jethro]

Most folks who shoot smaller game like what most of the North American stuff is, with lighter bullets, tend to favor the FPE method of calculating energy. This formula tends to favor lighter faster bullets.

However, folks who hunt larger dangerous game often tend to like the momentum formulas that favor heavy slower bullets.

So you can take you pick as to which you want to put more faith in, momentum or FPE. Are you a pumpkin roller or a super zapper? I feel both have their place, depending on the cartridges and game involved.

Now as to your example there, at 50 yards you will see very little difference in the killing power of those 2 cartridges. But at 200, after BC takes over and significantly influences the impact speed and drop, there will be a significant difference.

[Ronnie41]

Those are not similar speeds.

[TxAg]

Those are not similar speeds.

I think this is the ticket. I assumed 200 fps wasn't as big a difference as it actually is.

[tigerscowboy]

It is greatly significant IMO.

Suggest looking at the differences at 200 yds. Then compare the accuracy differences.

Now compare at 300 yds.

[RJH1]

Here is the funny thing, in my experience 30-30s kill better than 308s. I am not talking at 300 yards, more in the line of 150 and less, where more deer are killed. I think it is the round noes bullet mushrooming quicker, but not sure. To be fair I have not shot a 308 with a RN bullet, because that defeats the purpose of the 308. Also the 3006 seems to hammer deer better than anything else I have used, although the only mag caliber I used was a 7 rem mag and the 06 seemed better. This is just what I have personally seen over quite a few deer, but your mileage may very

[Slick8]

It is significant. Here's my example of just how significant.

Let's take your .308, specifically a 175 Berger and give it a minimum velocity threshold of 1800 FPS which is common to most bullets for terminal performance on game.

At a 308win mv of 2600 fps it falls to 1800 at 460 yards. At a 300wm mv of 2950 it's good to 640 yards. That's with a difference of 350 fps at the muzzle.

The 350 fps gained you an additional 180 yards of terminal performance.