Rebarrel to fast twist 270 Win or go 6.8 Western?

[Gorp2007]

Then explain the difference in velocity and energy to me between these two loads. And explain to everyone why you think the 129 would perform better than the 155 on elk at each incremental distance past 400 yards. Assume a shooter mistake and the bullets are both going to hit the elk in the scapula.

Sure thing, friend!

The velocity of the 129 will be higher, so it’ll do a better job of opening up at any distance where the velocity remains higher.

Energy only matters as a factor of velocity, so the comparison is irrelevant unless you’re using directed energy weapons.

Either one will punch through an elk scapula, so it’s as irrelevant as energy. Plenty of photographic evidence of bullets punching through elk shoulders if you bother to look around.

Good luck and let us know if you decide to do something interesting!

 

[bmart2622]

Velocity does dictate energy but so does bullet weight. They work in combination. The heavy high bc bullets hold velocity longer and with the weight also have more energy at range

And velocity dictates bullet expansion

 

[bmart2622]

Velocity x velocity x mass does not equal force. Change in velocity x mass = force (energy).

Do yourself a favor before you look even more foolish and put your foot even further in your mouth and google the calculation for finding a bullets ft/lbs of energy

 

[alpinewanderer]

Do yourself a favor before you look even more foolish and put your foot even further in your mouth and google the calculation for finding a bullets ft/lbs of energy

Okay. We both have our foots it our mouths because we are not being precise about our language here. If you are talking about energy, more properly kinetic energy, then the formula is 1/2V^2*m. That's half the square of the velocity times the mass. In damaging things with projectiles we are interested in the transfer of momentum from the bullet to the object. As you've shown yourself mass is also a component of energy. So if the velocity increases and the mass stays the same, you have an increase in energy. You can also increase the energy if the velocity is constant and you then increase the mass. Velocity doesn't kill elk and deer, the transfer of energy or more properly, transfer of momentum kills deer. I think people are interested in velocity because by increasing it you can get more energy using the same bullet weight. But a lighter bullet generally won't retain its momentum over a longer distances. Hence you can see that the 155 gr bullet above has more retained energy at 600 yards than the 129 gr bullet.

I don't know how, when looking at two projectiles of identical diameter and identical construction but different weights that one could think the projectile with less kinetic energy would transfer more of that energy to a target than one that has more. At 500 yards both a Barnes 129 gr. LRX and a 155 gr. LRX have the velocity to expand almost instantaneously but one has more KE than the other. If the bullets only touch skin and organs both would probably work fine. But if they touch dense and thick bone the one with more KE is more likely to break through and keep moving into the animal.

Shot placement and bullet design and construction have a lot to do with energy transfer but it seems like a lot of you guys are kind of stuck on velocity only. Shot placement, bullet construction, BC, SD, frontal diameter, bullet weight, and velocity all play a role. I said from the beginning that I'm using 129s right now and would like to shoot 155s fast enough to produce more KE than my max charge for the 129s. Based on the ballistic data from Barnes, I get all the ballistic benefits of the 129 gr. but with a 155 gr. AND I get more KE farther out with the 155. Both the 129 and 155 are traveling fast enough to almost instantaneously expand completely on impact at 500 yards.

Hence the interest in the faster twist 270 Win. Still nobody has had anything to say about the 6.8 Western which is the other chambering I am considering. I expect because none own or have used it.

 

[bmart2622]

Well since we are on Rokslide and this is in a Firearms section it would seem pretty self explanatory that we are talking about ft/lbs of energy acheived by a projectile, so, again, your foot is in your mouth. So how do you explain the dozens and dozens of animals killed, complete with necropsy photos on this website alone, caused by projectiles that fall below your Fudd Lore threshold of 1500ft/lbs of energy?

 

[fuzzymarindave]

Okay. We both have our foots it our mouths because we are not being precise about our language here. If you are talking about energy, more properly kinetic energy, then the formula is 1/2V^2*m. That's half the square of the velocity times the mass. In damaging things with projectiles we are interested in the transfer of momentum from the bullet to the object. As you've shown yourself mass is also a component of energy. So if the velocity increases and the mass stays the same, you have an increase in energy. You can also increase the energy if the velocity is constant and you then increase the mass. Velocity doesn't kill elk and deer, the transfer of energy or more properly, transfer of momentum kills deer. I think people are interested in velocity because by increasing it you can get more energy using the same bullet weight. But a lighter bullet generally won't retain its momentum over a longer distances. Hence you can see that the 155 gr bullet above has more retained energy at 600 yards than the 129 gr bullet.

I don't know how, when looking at two projectiles of identical diameter and identical construction but different weights that one could think the projectile with less kinetic energy would transfer more of that energy to a target than one that has more. At 500 yards both a Barnes 129 gr. LRX and a 155 gr. LRX have the velocity to expand almost instantaneously but one has more KE than the other. If the bullets only touch skin and organs both would probably work fine. But if they touch dense and thick bone the one with more KE is more likely to break through and keep moving into the animal.

Shot placement and bullet design and construction have a lot to do with energy transfer but it seems like a lot of you guys are kind of stuck on velocity only. Shot placement, bullet construction, BC, SD, frontal diameter, bullet weight, and velocity all play a role. I said from the beginning that I'm using 129s right now and would like to shoot 155s fast enough to produce more KE than my max charge for the 129s. Based on the ballistic data from Barnes, I get all the ballistic benefits of the 129 gr. but with a 155 gr. AND I get more KE farther out with the 155. Both the 129 and 155 are traveling fast enough to almost instantaneously expand completely on impact at 500 yards.

Hence the interest in the faster twist 270 Win. Still nobody has had anything to say about the 6.8 Western which is the other chambering I am considering. I expect because none own or have used it.

I’m big on velocity and would prefer both entry and exit holes over dumping all bullet energy into animal. I shoot 6.8 Western and it was pointed out that the case rim is too large for your bolt face. Just get a fast twist .270 Win or try a rebated rim cartridge if you want more velocity. 270-284 Win was mentioned. Or maybe be the first with a 6.8- 6.5 Weatherby RPM.