Ballistics Question

billyc

billyc

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Ok this is probably a stupid question but I keep reading all the different vs. threads on here and will this be enough gun to shoot a sabre tooth tiger etc.
I was looking at picking up a new rifle and was studying ballistics on the 308, 30/06 and 270wsm.
On federals website they show that at 300 yards the 308 imparts 1789fp's in a 180gr trophy bonded tip. In the 30/06 in the same bullet it shows 1911fp's. Finally in a 270wsm it shows 1988 fp's in a 130gr trophy bonded tip.
So does this mean that a 270wsm has more knockdown power then the other 2? I researched the 338 federal and it shows that at 300 yards a 210 nosler is 1878fps.
After looking at that I assume the bigger the pill the more whomp there would be.
Sorry again if this is a complete moronic question.
Billy
 
No it's not moronic. Your looking at feet per second. (FPS) I think your more interested in foot pounds of energy. Generally speaking, the heavier bullet traveling at higher velocity (FPS) has more "knock down power".

In reality, you should be more interested in your particular bullet having enough velocity at a given range to expand correctly and impart as much damage as possible. That will vary by bullet and cartridge. :wave:
 
I think those numbers are in fact foot-pounds, right Billy?

To my way of thinking, they are all about the same. The question might be "which one is better at transfering that energy to the target?" And for similar bullet designs, the larger diameter bullets should be able to transfer the energy more efficiently, at least as I see it.

RG
 
... I should have qualified "all the same" a little better. I meant all the same in terms of similar enough amounts of retained energy that other factors (perhaps trajectory, or other components of terminal performance, such as bullet diameter) will probably become more important in your consideration of which is best for your next rifle.

RG
 
Impact energy is mass (grains of bullet) times velocity (FPS) squared, divided by 225218. Essentially, a bigger bullet flying faster, hits harder. Sectional density factors into downrange knock down power as well.
 
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While foot pounds of energy are a useful means of comparison between cartridges, the numbers don't mean a great deal when we are interested about how a bullet acts on living tissue. The construction of the bullet ultimately determines if the wound will be wide and shallow or narrow and deep and in addition to this the expanded diameter of the bullet combined with it's momentum determines the wound volume. Generally speaking, although this is not universally true, the heavier the bullet the larger the expanded diameter of the bullet and the most momentum there is to drive the bullet through the target. Varmint bullets tend to be explosively fragile, light weight, and very fast. This is important to prevent ricochets, but also to cause massive unsurvivable wounds to small animals. African dangerous game bullets are often solids that produce narrow but very deep wound channels. Most medium sized game is taken with some sort of expanding bullet that ensures deep penetration (with respect to the size of the game animal) and causes a large wound cavity that leads to massive blood loss resulting in a fast humane kill, if the POI is correct.

For North American game, a minimum of a .25 caliber 120 gr expanding bullet with an impact velocity of 2000 fps will take all but the big bears and bison. .270's and 7mm's have a great reputation for flat trajectory, and no bullets cover a greater range than the .30's.

Given the rounds that you have shown interest in, the .308 is a great cartridge if your want a short light rifle and intend to hunt game in the 400 pounds class or smaller. The .30/06 is useful for game up to 1500 pounds due to it's ability to drive heavy bullets at moderate velocity. The .270 WSM would be a good choice if you intend to hunt medium sized game beyond 350 yards. Everyone has their own ideas about what is the best for what, but in very general terms this might give you an idea of how things work.
 
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