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.

 

[alpinewanderer]

I built a fast twist .270 with a long throat usually load just under 3.6. everyone says don't do .277 for bullet choice but I've found if you shoot monos (I live in California) that is absolutely not true and every nonlead manufacturer has good options for heavy .277.
Right now I'm shooting badlands bulldozer 140s at 2950 which keeps me above 2k out past 1k with low recoil though that's way past my comfortable range

Wow.

 

[alpinewanderer]

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?

Dude, I've killed animals with a weapon with an order of magnitude less KE than 1500 ft-lbs. It's my compound bow. But that 514 gr arrow and broadhead combo are also probably an order of magnitude less forgiving. KE buys forgiveness. The bow and arrow allow for a very narrow window of shot angles, vital hit options, and distances, compared to a centerfire rifle. I've killed 13 big game animals up to and including elk with .270 win mono metal bullets and kept my shots close enough to meet that KE threshold. 12/13 were one shot kills. I've really liked that track record. Maybe your right, maybe I'm being too conservative and monos and just way more powerful with the penetration abilities for me to worry about shooting farther than 400 with a 129 gr.

But things go wrong man. If you hunt you know. During one of those shots a longer one (~400 yards I think it was) the elk must have moved its leg or I jerked the shot and the bullet went crashing through the front leg. It killed the animal right there but it absolutely wrecked the meat of the front right quarter with clotted blood and bone fragments and didn't get much from it. So I wonder what could have happened if I took that shot from 200 farther away. Could it have been a wounding?

So why come into this thread with hostility and a mocking tone? I never said you were an immoral guy if you shoot elk when your bullet has less juice than 1500 ft lbs. I'm saying I just don't want to.

And what I really want are helpful insights into 1:7.5 .270 Win vs. 6.8 Western, which you never gave.

 

[alpinewanderer]

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.

I can always just get a magnum bolt for the tikka. Let's not consider that a factor. Do you still think the fast twist 270 Win would be a better choice than the 6.8 W?

 

[Koda_]

And what I really want are helpful insights into 1:7.5 .270 Win vs. 6.8 Western

The "performance" section of the Wikipedia article of the 6.8 Western directly compares its ballistics to the standard 270 (If I read correctly comparing a 150gn bullet respectively...). Note: the 6.8 uses a fairly fast 8 twist barrel by its design to stabilize heavier ie higher BC bullets, 165-175gn.
I think if you want to compare the two calibers head to head, the 6.8 "wins" by the numbers only but if you wanted to breath some life into the equally qualified 270 improving it with a modern chamber and fast 7 twist will give you options that are virtually equal to the 6.8.
I think.. IMO, if you suped up your 270 it would be worth it to go with an Ackley Improved chamber as well to maximise its potential with the heavier higher BC bullets.

At the end of the day comparing calibers your splitting hairs here, your two contenders are more than enough as is for any big game in North America... except you've lamented the sentimental value of your beloved 270 and to me that has merit. You have memories with it, enjoy it, it sounds like what you shoot best. The barrel/chamber upgrades to it will not hinder shooting traditional bullets or loads in the 270, especially with monolithics that cant be overspun. Recently, the advantages of faster twist rates were shared in a post by Bryan Litz I think would be of interest to you, in short its an advantage. The fast twist 270 guy above validates that, as youve noted impressive results already.

My vote is for your 270 with a 7 twist and throated long will give you a traditional caliber that hits way above its class with the modern 6.8...

https://www.facebook.com/BryanLitzBallistics/posts/pfbid0tTVTNnsEP8PFDYGkY9wtVvYkWgNQo8kyXSbxn9TiD2CT1wpNsv6ugmSU1u6SbN87l

 

[AZ_Hunter]

The factory tikka mag will limit your COAL with really long bullets. If you do the fast twist consider that, and look at different bottom metal and mags.

Another option would be a 270-284 Win wildcat. Then you could use your standard LA tikka mag and bolt, but be able to use the longer bullets.

 

[Macintosh]

@alpinewanderer in case you havent noticed this has been hashed out more or less monthly here so folks are kind of sensitive about it.

The calculated energy is the same between a fmj and a hunting bullet, and the fmj doesnt transfer hardly any of it to the animal. So the simplest formula for energy is not predictive of killing effect because it doesnt account for the type of bullet.

Looking at different hunting bullets there are oodles of scientific papers detailing that they expand and fragment differently in tissue, and therefore they create different sized holes in the animal. Again, while it is energy that is doing the “work” of creating a lethal wound in the animal, its the bullet construction that determines how each bullet behaves differently and how it creates a bigger or smaller hole in the animal. It is the amount of tissue damage that determines how it ultimately performs, even the research on hydrostatic shock shows that it exists but only in very close proximity to the wound channel, and that it isnt a significant factor in incapacitating the animal. This is all direct from multiple scientific papers that have been linked to various threads on this site, so its all searchable. You are correct that the rate at which a bullet slows, and the physical mechanism that it uses to do so, is what determines how big of a wound it makes—basically the above research showed that bullet construction and how that bullet behaves in tissue, is what determines how big of a wound it makes. It means that at any given “kinetic energy” figure for a bullet based on its mass and velocity, you can get small narrow wounds, or large gaping wounds, all based on the construction of the bullet—but not based on the energy. In other words the energy is not predictive of the damage. It IS true that a bullet with more energy has the possibility of doing more damage, but only as much as that bullet type is capable of creating—a low-energy bullet that explosively fragments creates a larger wound than a high-energy bullet that only creates a narrow wound channel. Some bullets even introduce multiple mechanisms of injury, combining the “splash” you alluded to with small bullet fragments that further cut tissue during the stretch, thereby amplifying the volume of the wound channel. This is all why folks are saying kinetic energy is irrelevant. You have some reading to do, Id take a spin through the 223 for big game thread and the why match bullets for hunting thread to get the gist of it. But you are also not going to be dealing with loss of mass from fragmenting, which is one reason the heavier lead bullets are good— a 150gr lrx is not going to make a bigger wound than a 130 lrx, both are going to make a narrow, deep wound and then likely to catch on the off-side hide, so at that point folks are mainly concerned with expansion velocity to ensure it doesnt pencil.

Also on ballistics—copper has a low bc compared to lead, so the heavier bullet mantra doesnt always transfer. You’ll have to have the bc and velocity of the different bullets and plug them into a ballistic calculator to see where they run out of enough velocity to expand properly. Those copper monos require enough velocity to expand or they will pencil. You may find that you can handload so the 150-class lrx’s carry velocity farther, but its entirely possible it wont work out that way. I also shoot copper and most times I have checked its not the heaviest copper bullet out of a given cartridge that carries its velocity to longer range. You just have to run the numbers and find out.

Lots of folks are having a flared collar threaded onto their thinner barrels so they can add a can on 5/8-24 threads. Someone shoukd be along shortly to recommend someone who can do this.

 

[Highvoltage1]

The factory tikka mag will limit your COAL with really long bullets. If you do the fast twist consider that, and look at different bottom metal and mags

I’d consider this first, tikkas are limited by their mag box. A 155 lrx is going to be very long so it needs to be single fed and to get the velocity up you need something similar to rl26 with a straight 270.

6.8 or 270wsm (fast twist) would be a better option, that would require barrel, bolt and possibly a mag if your set on the 155 lrx or similar mono

Bullets to consider to reach your goals with confidence and with no mods…

129 lrx
150 ablr
145 eldx
150 sst
Any Berger minus 170 eol

Scrap the idea of energy on target and focus on the manufactures recommendations for minimum expansion velocity. Best wishes

 

[mlevimadden]

If you’re wanting to run heavy monos you can also look at a 270 WSM to be less hampered by COAL in the tikka but it can be tough to find components for.

If it were me, I’d stay with the 270 win chambering and get a faster twist barrel threaded for a suppressor to stabilize the 145 eldx or 150 vld. This will keep your recoil manageable, extend your effective range way farther than the monos getting the 1900 fps minimum velocity rather than 22-2400 for the monos, and give you way better wound channels (and energy transfer since you seem concerned with energy).

 

[fuzzymarindave]

I can always just get a magnum bolt for the tikka. Let's not consider that a factor. Do you still think the fast twist 270 Win would be a better choice than the 6.8 W?

I like the aesthetics of the 270 Win/30-06 cartridges and I scratched that itch with a 280AI. For the .277 caliber I don't have a fast twist 270 to compare but looking at load data the 6.8 Western will get you easily get 150 fps more but you will have one less cartridge in the mag because they are fat. Either will get the job done..

 

[Koda_]

Dude, I've killed animals with a weapon with an order of magnitude less KE than 1500 ft-lbs. It's my compound bow. But that 514 gr arrow and broadhead combo are also probably an order of magnitude less forgiving. KE buys forgiveness. The bow and arrow allow for a very narrow window of shot angles, vital hit options, and distances, compared to a centerfire rifle. I've killed 13 big game animals up to and including elk with .270 win mono metal bullets and kept my shots close enough to meet that KE threshold. 12/13 were one shot kills. I've really liked that track record. Maybe your right, maybe I'm being too conservative and monos and just way more powerful with the penetration abilities for me to worry about shooting farther than 400 with a 129 gr.

I see the bow comparison occasionally and its not a comparison, they kill entirely differently thru hemorrhaging especially if the animal runs they get sliced up from the inside out. Bullets kill by blunt force destroying critical internals in its path.

Listen to the guys here about velocity. The reason those monos worked so well for you is not because you stayed close enough to be above 1500ft lbs, its because they opened up from the hydraulic effect filling the hollowpoint which only happens with enough velocity. Monos are incredibly effective this way as a solid, you stay above their velocity threshold and they will kill very reliably.

If you put a 7 twist on your 270 to push the heavier monos fast you will greatly improve the calibers potential. Heavier monos are longer which also increases their sectional density which improves penetration on larger game, add that with the higher BC of the longer bullet and you wont look back.

 

[SloppyJ]

Well this was a fun read

 

[TaperPin]

The "performance" section of the Wikipedia article of the 6.8 Western directly compares its ballistics to the standard 270 (If I read correctly comparing a 150gn bullet respectively...). Note: the 6.8 uses a fairly fast 8 twist barrel by its design to stabilize heavier ie higher BC bullets, 165-175gn.
I think if you want to compare the two calibers head to head, the 6.8 "wins" by the numbers only but if you wanted to breath some life into the equally qualified 270 improving it with a modern chamber and fast 7 twist will give you options that are virtually equal to the 6.8.
I think.. IMO, if you suped up your 270 it would be worth it to go with an Ackley Improved chamber as well to maximise its potential with the heavier higher BC bullets.

At the end of the day comparing calibers your splitting hairs here, your two contenders are more than enough as is for any big game in North America... except you've lamented the sentimental value of your beloved 270 and to me that has merit. You have memories with it, enjoy it, it sounds like what you shoot best. The barrel/chamber upgrades to it will not hinder shooting traditional bullets or loads in the 270, especially with monolithics that cant be overspun. Recently, the advantages of faster twist rates were shared in a post by Bryan Litz I think would be of interest to you, in short its an advantage. The fast twist 270 guy above validates that, as youve noted impressive results already.

My vote is for your 270 with a 7 twist and throated long will give you a traditional caliber that hits way above its class with the modern 6.8...

https://www.facebook.com/BryanLitzBallistics/posts/pfbid0tTVTNnsEP8PFDYGkY9wtVvYkWgNQo8kyXSbxn9TiD2CT1wpNsv6ugmSU1u6SbN87l

I don’t see the Brian Litz video telling the whole truth. The comparison with a barrel twist that the bullet manufacturer says is too slow to stabilize the bullet, isn’t really helpful - I’m surprised the bullets even made it to the long distance target since many under stabilized bullets barely hit paper at short range, let alone mid range and beyond. Sierra says that bullet should only be used in 1:9 and faster barrels. What he showed isn’t wrong, it just doesn’t matter when the bullet would usually be so inaccurate it doesn’t make it to the target.