Bullet weight v.s FPS and FT/Lbs

[Mike_W]

Ok so after looking into some ballistics on the winchester website (they have a neat little ballistics calculator) I have come to the understanding that fps and bullet weight determine the ft/lbs for instance a 130 grain barnes shot out of a 270 WSM will hit with more force than a 140 grain accubond. My conclusion was the barnes is shot at a higher velocity therefore creating my ft/lbs of force.

So I suppose my question would be that I was wanting to use a "heavier" bullet to get as much "punch" out of my 270 WSM as possible but I guess sometimes a lighter bullet will hit harder? Any reason I should go with a 140 or 150 over a 130 in this gun?.....especially if the 130 hits harder?

Thanks,
Mike

[PoppaW]

ft/lbs are real hard to use to describe 'punch'. If you use a 130 TSX and compare to a 140 TSX out of the same gun and the ft/lbs are more for the 130 then you may have something. I hate the ft/lbs because it biases speed. Speed does kill but so do good bullets in the right spot. The shape of the bullet, in my opinion has a more drastic effect on animals than ft/lbs. To smack something beyond what the ft/lbs show in a chart use a tough flat nose bullet in a bigger caliber. I don't know what yard stick to use for what you are asking. Much more to it than speed and bullet weight.
I have found most of the bullets that kill best aren't the flattest shooting.

[Dick284]

Bullet construction will throw every ballistics table pretty much into disaray.

A stoutly constructed bullet operating within it's design paprmeters will out penetrate a less stoutly constructed bullet of the same weight. Worse yet move the bullet perfomance beyond it's design parameters and all bets on sound performance will go south.

Bullet weight also has the added benifit (if construction is similar) of generally having the heavier bullet (even with some what less kinetic energy) of out penetrating the lighter bullet.

Cartridges with muzzle velocites of no more that 2800fps, generally will perfom quite well regardless of bullet construction.

Move over the 3000fps threshold and your into a much more different game.

This is why bullet selection is so important.

[Homesteader]

Kinetic Energy, and momentum are two different things. I wouldn't get too hung up on the lighter bullet showing more energy, which when calculated it certainly does. Think of it like Horsepower, and Torque. The big diesels can just about always do more work even though they may not have the highest horsepower. Clear as mud right?

[BallCoeff.435]

Many rifle calibers have a certain 'favorite' bullet weight, for instance the .300 win mag usually likes a 180 spire point the best. Sure, you might get all sorts of bullet weights from 150 to 220 I suppose, but unless you're restricted to one rifle and have special reasons for going really fast or really heavy, it's best to stick with the 'favorite weight'. That would bracket muzzle velocity at around 2800 - 3000 fps.

Then just work up loads for that weight in one or more of your preferred hunting bullets.

If there's a good enough reason for substantially more 'punch' at lot of times, then probably the best solution is a larger rifle.

[hardy]

The reason faster bullets tend to have more energy right off the get go is because velocity is squared when determining the energy. The formula is Kinetic Energy=.5x(mass)x(velocity squared). If you look in the ballistics charts you will notice that the heavier bullets tend to have more energy farther down range, this is because lighter bullets shed velocity faster then heavier bullets. I would tend to agree with the statements already made that bullet construction has more to do with it then energy. If I were you see what shoots better in your gun the 130 or 140's, there's not going to be a lot of difference down range when an animal gets smacked by either one.

[Traps]

....I have come to the understanding that fps and bullet weight determine the ft/lbs for instance a 130 grain barnes shot out of a 270 WSM will hit with more force than a 140 grain accubond. My conclusion was the barnes is shot at a higher velocity therefore creating my ft/lbs of force.

So I suppose my question would be that I was wanting to use a "heavier" bullet to get as much "punch" out of my 270 WSM as possible but I guess sometimes a lighter bullet will hit harder? Any reason I should go with a 140 or 150 over a 130 in this gun?.....especially if the 130 hits harder?

Thanks,
Mike

Mike just want to correct your terminology before getting into your questions. The correct units when talking about energy are ft-lbs (ft times lbs not ft divided by lbs) This at first glance seems misleading because it is the dimensional equivalent to torque which is also ft-lbs but the two are entirely different in that energy is a scalar quantity whereas torque is a vector quantity. You can add and subtract vector quantities to get a net result. Example would be you have 10 ft-lbs of torque acting counterclockwise and you have 2 ft-lbs acting counterclockwise, the net torque is 8 ft-lbs. Scalar quantities like energy are treated as before and after events not like torque which is this and that equals a result. Energy is treated as a before and after where energy in equals energy out.

Now back to your question if your talking about force this is entirely different than ft-lbs which is energy. Force is the product of mass times acceleration which in this case would be the negative acceleration of the bullet as it hits the animal's tissue. Energy on the other hand is mass times velocity squared, this is why velocity yields larger energy values than larger mass.
So the 130 grain bullet yields higher energy, not force.

To explain more punch by a lighter bullet - if you take two bullets one at 130 grains and one at 150 grains and their construction was the same and you shot them you would get "more punch" with the lighter one over the heavier one. Velocity dictates the amount and rate of expansion. A higher velocity will cause the 130 gr bullet to expand larger and quicker than the 150 grain bullet. This higher velocity 130 grain bullet will transfer more energy into the animal and as well transfer more force as the bullet will decelerate more rapidly than the 150 grain bullet. This higher transfer by the lighter bullet is due to the increased resistance met by the larger expanded frontal area of the bullet.

So in laymans terms lighter bullets will provide more punch and less penetration than their heavier counterparts.

[Mike_W]

Mike just want to correct your terminology before getting into your questions. The correct units when talking about energy are ft-lbs (ft times lbs not ft divided by lbs) This at first glance seems misleading because it is the dimensional equivalent to torque which is also ft-lbs but the two are entirely different in that energy is a scalar quantity whereas torque is a vector quantity. You can add and subtract vector quantities to get a net result. Example would be you have 10 ft-lbs of torque acting counterclockwise and you have 2 ft-lbs acting counterclockwise, the net torque is 8 ft-lbs. Scalar quantities like energy are treated as before and after events not like torque which is this and that equals a result. Energy is treated as a before and after where energy in equals energy out.

Now back to your question if your talking about force this is entirely different than ft-lbs which is energy. Force is the product of mass times acceleration which in this case would be the negative acceleration of the bullet as it hits the animal's tissue. Energy on the other hand is mass times velocity squared, this is why velocity yields larger energy values than larger mass.
So the 130 grain bullet yields higher energy, not force.

To explain more punch by a lighter bullet - if you take two bullets one at 130 grains and one at 150 grains and their construction was the same and you shot them you would get "more punch" with the lighter one over the heavier one. Velocity dictates the amount and rate of expansion. A higher velocity will cause the 130 gr bullet to expand larger and quicker than the 150 grain bullet. This higher velocity 130 grain bullet will transfer more energy into the animal and as well transfer more force as the bullet will decelerate more rapidly than the 150 grain bullet. This higher transfer by the lighter bullet is due to the increased resistance met by the larger expanded frontal area of the bullet.

So in laymans terms lighter bullets will provide more punch and less penetration than their heavier counterparts.

Good Stuff Traps I guess it makes sence!! Thanks for the input guys!!