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You hear it quite a bit that a faster twist than what's necessary to fully stabilize a bullet in flight, helps with terminal performance once the bullet hits game. So for example, if perhaps a 9 twist gives a particular bullet an Sg of 1.5 or more, would an 8 twist give better terminal performance than the 9 twist once the bullet strikes game? I'm interested in what y'all think or better still, have experienced.
Um, no.
Perhaps in light weight varmint bullets which are pretty fragile to begin with...
Depends.
Is the game inhaling? Or exhaling?
šŸ˜³
Originally Posted by AKwolverine
Depends.
Is the game inhaling? Or exhaling?
šŸ˜³
Either one.
nope
So I suppose the theories could be along the lines that with a frangible bullet the faster twist might disperse the pieces further and faster and cause more damage, and with a non frangible bullet the extra spin may help it in a denser medium, perhaps. I'm not saying these theories are valid, just putting it up for discussion.
Youā€™re talking ~ 12% difference in rpm.
Yet a 12 % difference can make a big difference in stability during flight (at the margin), so its not unreasonable to speculate whether it makes a difference in terminal performance.
Too fast or too slow a twist for a selected bullet is never a good thing
No. SG in the atmosphere has nothing to do with terminal ballistics.
We know the effects of too fast or too slow a twist for a selected bullet in flight, but the ideal twist for a bullet once it strikes game which is considerably different to the medium of air, doesn't seem to have been studied much, or if it has, I am not aware of the findings.
Heres some of my observations of rifling twist:

Had a 1:9.5" rifling barrel on a 9.3x62. With 300 grain swift-aframes, the recoil was stout.

In a 9.3x62 with a 1:14", the recoil was less, and those same 300 grainers recovered from moose and caribou shot a 400-500 yds expanded wonderfully.

In a savage 99 308, with 1:12 rifling, some 200 grain bullets would key-hole the target.

In a ruger 308 with 1:10 rifling, itll stack those same 200 grainers into quarter inch groups.
Grabbing some popcornā€¦

I tend to like more RPMs myself. Old Bill Steigers was a nut about RPMs with his Bitterroots, shooting a lot of them into media and believed the faster they turned the better they worked.

Probably doesnā€™t matter much, but Iā€™ll always take more RPMs vs just enough.
And that's the thing, I've heard the same thing from several very experienced hunters to not just dismiss it as fallacy.
Watch some ultra slo-mo videos of projectiles hitting gelatin and you can see creases in the gelatin caused by the deformed bullets. See if you can see how many revolutions the bullet makes before it stops.
Originally Posted by beretzs
Grabbing some popcornā€¦

I tend to like more RPMs myself. Old Bill Steigers was a nut about RPMs with his Bitterroots, shooting a lot of them into media and believed the faster they turned the better they worked.

Probably doesnā€™t matter much, but Iā€™ll always take more RPMs vs just enough.

It matters in both directions.

The original AR-15 had a slow for cartridge 1-12 twist and bullets would tumble enhancing the termial performance of M193.

Ross Seyfried told me he prefered a 1-10 or 1-12 twist on his .416 Remington as solids would penatrate straighter and not tumble. I think he may have convinced Remington to go to a tighter twist than the original 1-14.

A fast twist does have epanding bullets expanding a bit faster.
Originally Posted by JohnBurns
Originally Posted by beretzs
Grabbing some popcornā€¦

I tend to like more RPMs myself. Old Bill Steigers was a nut about RPMs with his Bitterroots, shooting a lot of them into media and believed the faster they turned the better they worked.

Probably doesnā€™t matter much, but Iā€™ll always take more RPMs vs just enough.

It matters in both directions.

The original AR-15 had a slow for cartridge 1-12 twist and bullets would tumble enhancing the termial performance of M193.

Ross Seyfried told me he prefered a 1-10 or 1-12 twist on his .416 Remington as solids would penatrate straighter and not tumble. I think he may have convinced Remington to go to a tighter twist than the original 1-14.

A fast twist does have epanding bullets expanding a bit faster.

I think so myself John. Very familiar with the ARā€™s and once the 1-7ā€™s and 77 SMKs were available those were game changers.

And yeah, it makes sense on the big guns too, as a stabilized bullet should stay on point better than a marginal one.

I think itā€™s a cool topic myself. Never seen many folks say ā€œman, I wished I had a slower twist cause my bullets went too straightā€. Maybe back before before bullets were so good, but it doesnā€™t seem like a thing nowadays.
Is the OP referring to increased rotation creating more centrifugal force which tears a bullet apart more and thus causing more damageā€”-or just more rotation causing a bullet (or the shank if it expands) to penetrate straighter?
Originally Posted by T_Inman
Is the OP referring to increased rotation creating more centrifugal force which tears a bullet apart more and thus causing more damageā€”-or just more rotation causing a bullet (or the shank if it expands) to penetrate straighter?

Not sure, but I tend to think both occurs because of RPMs.

But I am still learning so I like to hear others thoughts.
I have pondered this myself.

If the petal of an x bullet does a complete rotation in 12" the length of the laceration would be less than if it made a full rotation in 8" if they both penetrated the full chest cavity(?). I know, groan.

What about a partition shedding its front core? Do those fragments travel further with more energy with higher RPM?

What I really need to know is, where does the white go when snow melts? (OK, needless sarcasm)

I would be willing to bet some gun writer of old has actually tested this theory some how. Might be a ho-hum theory or might actually be revealing.
Originally Posted by T_Inman
Is the OP referring to increased rotation creating more centrifugal force which tears a bullet apart more and thus causing more damageā€”-or just more rotation causing a bullet (or the shank if it expands) to penetrate straighter?
I am referring to all possibilities including petals flying off at an increased velocity because of the additional rotational force and causing more damage, the frangible bullets tearing apart more, less tendency to tumble and drill through better, greater displacement of fluids and muscle from the wound channel, and anything else. All assuming the bullet was stable in flight in both the slower twist as well as the faster twist.
Originally Posted by mainer_in_ak
Heres some of my observations of rifling twist:

Had a 1:9.5" rifling barrel on a 9.3x62. With 300 grain swift-aframes, the recoil was stout.

In a 9.3x62 with a 1:14", the recoil was less, and those same 300 grainers recovered from moose and caribou shot a 400-500 yds expanded wonderfully.


In a savage 99 308, with 1:12 rifling, some 200 grain bullets would key-hole the target.

In a ruger 308 with 1:10 rifling, itll stack those same 200 grainers into quarter inch groups.

Were the overall weights, weight distributions, stock materials and stock configurations identical for those two rifles?
I would also add that the theory would be that the increased damage done by the increased rotation of the bullet is not totally negated by the slight decrease in forward velocity (and hence decrease in damage caused by a slower forward velocity) caused by the faster twist.
Does faster twist slow a bulletā€™s velocity, even if slightly?
On the flip side, could it build more pressure due to spinning faster in the bbl? More pressure equals more velocity, after all.
My head hurts.
Originally Posted by Riflehunter
Originally Posted by T_Inman
Is the OP referring to increased rotation creating more centrifugal force which tears a bullet apart more and thus causing more damageā€”-or just more rotation causing a bullet (or the shank if it expands) to penetrate straighter?
I am referring to all possibilities including petals flying off at an increased velocity because of the additional rotational force and causing more damage, the frangible bullets tearing apart more, less tendency to tumble and drill through better, greater displacement of fluids and muscle from the wound channel, and anything else. All assuming the bullet was stable in flight in both the slower twist as well as the faster twist.

In the case of more damage to a critter, I do believe so at least with expanding bullets. Centrifugal force is a thing for sure.
Originally Posted by T_Inman
Does faster twist slow a bulletā€™s velocity, even if slightly?
On the flip side, could it build more pressure due to spinning faster in the bbl? More pressure equals more velocity, after all.
My head hurts.
The way I think it works is that in a faster twist barrel velocity is slightly decreased and pressure is slightly increased if using the same load. The increase in pressure causes the bullet to increase in velocity, but not by as much as the decrease in velocity caused by the faster twist. The result is a slight over-all decrease in velocity. But I could be wrong...
Do you understand how to calculate the amount of energy tied up in the rotation of the projectile? It's a tiny fraction of the total kinetic energy of the projectile.

If I remember right going from a 12" twist to a 10" twist in a 2600 fps 308 load will rob something like 2 fps.
This is just an opinion, but I suspect without absolute knowledge that the effect of the rotational velocity of a bullet hitting an animal at 2,000 ā€“ 3,000 fps is minimal. I think it is the forward velocityā€”and the resistance to thatā€”which primarily causes (1) the expansion of the bullet; and (2) the lateral destruction of tissue in the unlucky animal recipient.

As to the expansion rate, I think the forward velocity in thousands of feet per second is the primary motivator.

As to the lateral impact on tissue: The tissue in front of the high-velocity bullet must go somewhere else. It is forced laterally to the side which destroys even more tissue outside of the bullet path. The degree to which this happens at any instance primarily is dependent on: (1) the forward velocity of the bullet; and (2) the shape/width of the bullet at that instance. Of course, the more mass the bullet has, the less that this velocity will decline, but thatā€™s another matter.

I think that the forward velocity of a large meplat expanding (or otherwise) bullet at high rifle velocities destroys tissue far outside the path of the bullet or any fragments from itā€”for the reasons described aboveā€”it blows tissue in front of it at extreme velocities to the side which destroys additional tissue outside of the path of the bullet or any fragments thereof.

For example, this is an exit wound on a deer from a 168gr .308 bullet.

[Linked Image from i.imgur.com]

It is so much larger than the bullet path or any petals (this was a cup and core) that the wound channel was not caused by rotation or metal flying off IMO. It was due to the forward velocity of the expanding bullet forcing the tissue in front of it to explode laterally, which destroyed additional tissue outside of the bullet path. A bullet rotating 12% more or less might have some impact, but I personally doubt that it is significant compared to the primary impact on bullet expansion and tissue destruction on the forward velocity and shape/construction of the bullet.

JMHO.
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.
MarineHawk - Totally agree.

Lou
The hammer bullet guys have been saying pretty heavy about you need min of 1.5sg for good terminal performance. Seems like this is has caught hold some lately on the net as I see it mentioned on and off. I debated this some with one of their guys and his belief was that the higher the sg the more ā€œpoint onā€ the bullet hits ensuring fluids get in the hollow point and open things up. It wasnā€™t really related to centrifugal force or stability in flesh like some older arguments. I wondered what he thought would happen if you hit a quartering shot that is much worse angle of impact than minute wobblings of a bullet but didnā€™t ask. Not poo pooing hammers by the way. Love the concept and have bunch to try. Just seems like
lot of noise of spin for terminal performance originating with that crowd lately

Lou
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
My only experience with this has been shooting roe deer with the same 65gr Sierra GK SBT bullets in two 22-250s, one 1:14" and one 1:8", and a 1:9.8 5,6x57 RWS.

Definetely, the bullets shot in the 1:8" 22-250 and the 1:9,8 5,6x57 expanded more violently, and penetrated less with more "splashing effect".

I believe John Barsness experienced the same effect on prairie dogs shooting 22-250s with different twists.
Originally Posted by mathman
Do you understand how to calculate the amount of energy tied up in the rotation of the projectile? It's a tiny fraction of the total kinetic energy of the projectile.

If I remember right going from a 12" twist to a 10" twist in a 2600 fps 308 load will rob something like 2 fps.

Thatā€™s what I remember seeing as well. Nothing actually measurable considering even an exactly the same barrel could account for the small measured change.

Also, I think folks believe if you have a 1-10 twist versus say a 1-7 the bullet is only turning 1 time in a buck or bull in 10ā€ of flesh.

If Iā€™m not mistaken forward velocity decays really quickly while RPMs do not.

You can see the effects of the RPMs on tougher bullets like an X bullet or Bitterroot. The frontal areas are sometimes turned almost 30-45 degrees from the shank. Iā€™d think this notes a bullet is rotating multiple times in media, bucks and bulls to bend those petals while blendering thru.

Just my observation.
Having seen bullets from a .220 Swift turn to smoke in flight and also make lead pinwheels on a paper target, I have no doubt that under the right circumstances: twist, velocity, core hardness, jacket; the integrity of the bullet and the effect on game can be affected by twist, as one factor anyway. Trying to deliberately take advantage of it in a systematic way would require some serious Loony Voodoo I suspect.
Fascinating subject and a good thread. I cautiously approach the topic from the perspective of MarineHawk. I'm a student not a teacher on this one. Looking forward to others chiming in...
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.
I personally think it does help...but that's just me. I do know that when you want to shoot a heavy for caliber bullet in a slower twist rifle, "speed is your friend". I.E. 45-70 with a 1/38" Marlin 1895 cut back to 20" and a 450+HC...when stabilized, will kick the snot out of you! Drop back to a 300gr around 1600...not so bad. On the lighter end, I noticed a slight difference between a slow twisted 22-250 and a fast twisted 22-250 AI on coyotes and PDs. In fact, I have seen PDs go "5 ft high and spinning to the right" with a fast twist 22-250AI and 68 Hornady OTM...awesome! ha
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...



[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]
[Linked Image from hosting.photobucket.com]


[Linked Image from hosting.photobucket.com]


1-8ā€ 7 Mashburn

Not sure how it kills any different but when you see the friction of the RPMs against the frontal diameter of the bullet it would seem to have to keep rotating in order to bend the petals in the propeller type way. If it was merely just turning over at the same rate of 1 turn in 8 inches I donā€™t believe youā€™d have that same effect, but Iā€™m just a student of this. Cool to see others points as well.

It does take a relatively robust bullet like the BBC or a heavy TTSX or similar to see it.

A standard bonded bullet like an Accubond or Swift doesnā€™t show as well since it doesnā€™t really have petals to bend as it sorta balls up.
It's a known fact that a lightly constructed bullet at high velocity and high RPM can disintegrate in flight.

So the answer in my opinion is yes, sometimes. There are a lot of variables though. Bullet construction, twist, impact velocity, impact medium, etc, etc.
Originally Posted by mainer_in_ak
Heres some of my observations of rifling twist:

Had a 1:9.5" rifling barrel on a 9.3x62. With 300 grain swift-aframes, the recoil was stout.

In a 9.3x62 with a 1:14", the recoil was less, and those same 300 grainers recovered from moose and caribou shot a 400-500 yds expanded wonderfully.

In a savage 99 308, with 1:12 rifling, some 200 grain bullets would key-hole the target.

In a ruger 308 with 1:10 rifling, itll stack those same 200 grainers into quarter inch groups.

I always wondered about this with heavier bulletsā€¦.Faster twist will have more recoil.
Originally Posted by shrapnel
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...

Once you have enough energy to expode the target like that it would be hard to expode it more.

This would be more about getting a bullet to expand that might be on the edge of not expanding and in larger animals that don't explode.

As Shane said it's possible to get bullets to expand on air if the twist is high enough and the jacket is thin enough.
Originally Posted by JohnBurns
Originally Posted by shrapnel
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...

Once you have enough energy to expode the target like that it would be hard to expode it more.

This would be more about getting a bullet to expand that might be on the edge of not expanding and in larger animals that don't explode.

As Shane said it's possible to get bullets to expand on air if the twist is high enough and the jacket is thin enough.

Are they expanding or simply coming apart? That is - they're not mushrooming but spinning apart where he jacket and core aren't 'mushroomed' but spun apart like a fidget spinner.
In the split second before a bullet comes completely apart, doesn't it expand? If the rotational force is excessive the bullet comes apart, but if not excessive it would just expand I would think.
Originally Posted by Riflehunter
In the split second before a bullet comes completely apart, doesn't it expand? If the rotational force is excessive the bullet comes apart, but if not excessive it would just expand I would think.

I took JB to mean "expand" in the common sense of a mushroom given the use of "expand on air" not "expand in air"
I do believe that the somewhat higher rotational speed of a bullet from the faster twist barrel does aid in the opening up of the bullet. To what degree I honestly do not have a clue. Whether or not it makes a difference in the demise of an animal may in the long run not mean much AFAIK.
Paul B.
Beretzs' photo of the non-fragmenting bullet is very convincing. It clearly shows how each of the petals is opened up more on one side than the other - indicating that at least some of the expansion was caused by rotational force rather than frontal force. It indicates that not only did the rotational force give more expansion, but also the "cutting effect" (caused by the shape of the petals) that rotational force would give in the larger wound channel.
I've asked many guys who Bitch about Bergers exploding on game what twist there running say 8 vrs 10 in a 30 cal not one would answer me. A 10 twist out of a 30 cal running 3050-3100 and a 215 isn't gonna act the same as a 8 twist.
Originally Posted by JohnBurns
Originally Posted by shrapnel
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...

Once you have enough energy to expode the target like that it would be hard to expode it more.

This would be more about getting a bullet to expand that might be on the edge of not expanding and in larger animals that don't explode.

As Shane said it's possible to get bullets to expand on air if the twist is high enough and the jacket is thin enough.

Varminting is the only reference I am applying my experience to, as the only time I have had others claim fast twist was more volatile than 1/12 or 1/14.

In big game, I have no comment, although the one picture of the bullet with twisted petals, does look like spin may have an effect. Making something more dead due to twist, may be similar to the caliber argument that never gets settledā€¦
Originally Posted by shrapnel
Originally Posted by JohnBurns
Originally Posted by shrapnel
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...

Once you have enough energy to expode the target like that it would be hard to expode it more.

This would be more about getting a bullet to expand that might be on the edge of not expanding and in larger animals that don't explode.

As Shane said it's possible to get bullets to expand on air if the twist is high enough and the jacket is thin enough.

Varminting is the only reference I am applying my experience to, as the only time I have had others claim fast twist was more volatile than 1/12 or 1/14.

In big game, I have no comment, although the one picture of the bullet with twisted petals, does look like spin may have an effect. Making something more dead due to twist, may be similar to the caliber argument that never gets settledā€¦

The answer might be "it affects terminal results" but no one can determine "help" or "hinder" at this point.
Originally Posted by PJGunner
I do believe that the somewhat higher rotational speed of a bullet from the faster twist barrel does aid in the opening up of the bullet. To what degree

I don't know whether it would make any difference in a big game bullet. I know for certain that when that when I rebarreled my 22-250 from a 12 twist to 8 twist that the impacts on prairie dogs got much more dramatic shooting the same bullet (55 gr ballistic tips) at roughly the same velocity. The bullets shot from the 8 twist seemed to expand quicker and give more dramatic theatrics from the hit prairie dogs.
I doubt that any animal killed by a bullet died as a result of twist. Iā€™m sure someone already said this earlier in the string, my fingers that they did, I love the debate aspect of it, not the results of it. Come opening day the Fire sings a different tune and thatā€™s music to my ears!
I just had a look at some mushroomed Barnes TSX's - .270 130 grain and .338 225 grain that I have. Both showed all the petals skewed in the direction of rotation. The point being that the rotational force has a significant effect on the 4 petals. I would conclude from that that a slightly greater rotational force would have a slightly greater effect.
Originally Posted by mainer_in_ak
...

Had a 1:9.5" rifling barrel on a 9.3x62. With 300 grain swift-aframes, the recoil was stout.
...
At what MV and rifle weight?
Bryan Litz did a FB post where he showed the difference in KE for rotational velocity of a 1-10 vs 1-12 bullet for a 250 gr bullet out of a 338 lapua and it was about 13 ft-lbs. keeping things equal the lineat KE was 13 ft-lbs less. His main point was faster twist does not result in much velocity loss. The point being the total KE stays the same if want to keep things equal by adding twist, linesr velocity will be little lower at same pressure. So, there are a few ft-lbs more rotational energy in a faster twist at the expense of linear KE. In a varmint bullet probably why see more pop. In a big game animal maybe shows as very slightly wider wound at expense of very slightly longer wound. However the vast majority of KE is still linear. In the case of the lapua it was 4348 linear / 29.3 rotational for 1-12 and 4335 linear / 42.1 rotational for 1-10

Lou
Originally Posted by Lou_270
Bryan Litz did a FB post where he showed the difference in KE for rotational velocity of a 1-10 vs 1-12 bullet for a 250 gr bullet out of a 338 lapua and it was about 13 ft-lbs. keeping things equal the lineat KE was 13 ft-lbs less. His main point was faster twist does not result in much velocity loss. The point being the total KE stays the same if want to keep things equal by adding twist, linesr velocity will be little lower at same pressure. So, there are a few ft-lbs more rotational energy in a faster twist at the expense of linear KE. In a varmint bullet probably why see more pop. In a big game animal maybe shows as very slightly wider wound at expense of very slightly longer wound. However the vast majority of KE is still linear. In the case of the lapua it was 4348 linear / 29.3 rotational for 1-12 and 4335 linear / 42.1 rotational for 1-10

Lou
Does it specifically say pressure was kept the same, and if so, do you know how he kept pressure the same? I would think he would need to drop the load slightly with the faster twist to maintain the same pressure.
Originally Posted by Teal
Originally Posted by shrapnel
Originally Posted by JohnBurns
Originally Posted by shrapnel
Originally Posted by TrueGrit
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
In the real world rotating an axe head slightly before impact helps tremendously. Rotating your fist before you hit someone inflicts cuts, and heavy hands. In other words a little twist goes a long ways in the real world.

I haven't witnessed any truth to that. I have shot 10's of thousands of gophers and other varmints and my observation is velocity with a certain amount of bullet mass, does the most damage. How fast twist could possibly blow something up more than this is speculation...



This is a triple...

Once you have enough energy to expode the target like that it would be hard to expode it more.

This would be more about getting a bullet to expand that might be on the edge of not expanding and in larger animals that don't explode.

As Shane said it's possible to get bullets to expand on air if the twist is high enough and the jacket is thin enough.

Varminting is the only reference I am applying my experience to, as the only time I have had others claim fast twist was more volatile than 1/12 or 1/14.

In big game, I have no comment, although the one picture of the bullet with twisted petals, does look like spin may have an effect. Making something more dead due to twist, may be similar to the caliber argument that never gets settledā€¦

The answer might be "it affects terminal results" but no one can determine "help" or "hinder" at this point.

I'd go with that. I just haven't found a spot where more RPM's hurts accuracy in hunting rifles with hunting or even ELD/VLD type bullets. I have heard of cut rifling being harder on some jackets, but not twist in and of itself.

I have been using 1-7 .224's, 1-8 264, 1-7 1/2 6mm, 1-8 308, 1-8 7mm, 1-10 375's, 1-10 9.3 etc for a bit and can't find the downside myself. I haven't vaporized any bullets and they've all done great with light bullets and especially with the heavier variety's.
No he did not say same pressure but same load. I inferred the same pressure part since linear velocity was deceeased for faster twist. So I would think if you want to keep same velocity pressure would increase

Lou
The thing is the velocity difference due to twist is lost in the noise.
I maintain the difference in terminal performance on game - going from a nine twist to an eight twist - is akin to the difference in terminal performance going from a 280 to a 280 ai. Is there a difference - sure. Is it meaningful ā€¦ ?

The 12 twist to 7 twist example is probably a bit more significant.
Originally Posted by Lou_270
No he did not say same pressure but same load. I inferred the same pressure part since linear velocity was deceeased for faster twist. So I would think if you want to keep same velocity pressure would increase

Lou
The actual difference in velocity between a fast twist and a slow twist is a little more when pressure is kept constant. I believe using the same load doesn't keep pressure constant, it increases pressure in the fast twist which tends to increase velocity, partially cancelling out the greater loss from a faster twist rate.
Originally Posted by AKwolverine
I maintain the difference in terminal performance on game - going from a nine twist to an eight twist - is akin to the difference in terminal performance going from a 280 to a 280 ai. Is there a difference - sure. Is it meaningful ā€¦ ?

The 12 twist to 7 twist example is probably a bit more significant.
Yes this is true, same as the difference between a .270 and .280 etc. Nevertheless its interesting to know whether it makes any difference at all or absolutely zero.
all things equal, I dont see why a faster twist WOULDNT impart more movement into the game.

that's why you spin a bowling ball - to impart "pin action" caused by that rotation, imparted from the ball into the pins.

that said, the ballistics of a bowling ball and a bullet are obviously radically different. smile interesting to think about, just the same.
Riflehunter;
Good evening to you sir, I hope the week was a fine one for you and you're well.

We've asked this question a few times here on the 'Fire over the years and I do mean to include myself in the "we".

This is from 2014.

https://www.24hourcampfire.com/ubbt.../tissue-damage-270-vs-6-5x55#Post9248055

In the years since that thread I've seen nothing that makes me change my mind, which is to say that I do believe that additional rpm do help certain types of bullet construction to work if not better, than more reliably.

All the best whichever twist you choose to use. grin

Dwayne
Originally Posted by mathman
Do you understand how to calculate the amount of energy tied up in the rotation of the projectile? It's a tiny fraction of the total kinetic energy of the projectile.

If I remember right going from a 12" twist to a 10" twist in a 2600 fps 308 load will rob something like 2 fps.
Like anything else it depends. Many long treatises have been written about this.

BTW this thread rocks. smile
Originally Posted by BC30cal
Riflehunter;
Good evening to you sir, I hope the week was a fine one for you and you're well.

We've asked this question a few times here on the 'Fire over the years and I do mean to include myself in the "we".

This is from 2014.

https://www.24hourcampfire.com/ubbt.../tissue-damage-270-vs-6-5x55#Post9248055

In the years since that thread I've seen nothing that makes me change my mind, which is to say that I do believe that additional rpm do help certain types of bullet construction to work if not better, than more reliably.

All the best whichever twist you choose to use. grin

Dwayne
Well thank you Dwayne, you are a true gentleman...I read the whole thread. Now I'm glad my .270 has a 1 in 9 twist, even though all the bullets I use only require a 1 in 10. I just need to determine whether I should go for a 1 in 10, 9 ,8 or 7 for a .257 with the intention of only using 110s which currently need only a 1 in 10.
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".

crazy

I would say that physics with its models and results are more than a little relevant to understanding how things work, in the case of ballistics as much as anything.
Originally Posted by mainer_in_ak
Heres some of my observations of rifling twist:

Had a 1:9.5" rifling barrel on a 9.3x62. With 300 grain swift-aframes, the recoil was stout.

In a 9.3x62 with a 1:14", the recoil was less, and those same 300 grainers recovered from moose and caribou shot a 400-500 yds expanded wonderfully.

In a savage 99 308, with 1:12 rifling, some 200 grain bullets would key-hole the target.

In a ruger 308 with 1:10 rifling, itll stack those same 200 grainers into quarter inch groups.
How difficult is it to use the 9.3 at 400-500yd distant? I've done years with the 308win and recently the 270win and big 338's but am curious about 9.3
Originally Posted by Jordan Smith
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".

crazy

I would say that physics with its models and results are more than a little relevant to understanding how things work, in the case of ballistics as much as anything.
BTW, here's that post I mentioned.

https://www.24hourcampfire.com/ubbt...m-compared-to-bullet-weight#Post16991752

I'll paste the text here:

"Okay. A few comments on the physics here.

First, in terms of the interior ballistics, let's assume a case in which we have a .224" 80 gr bullet being accelerated to a MV of 3000 fps, and the barrel has an 8" twist. For simplicity, I've approximated the bullet as a cylinder with a cone in front of it, where the cylinder and cone have equal lengths. In that case, the bullet leaves the muzzle with 7.5 joules of rotational kinetic energy and 2167.2 joules of translational kinetic energy. In other words, the rotational energy is 0.3% of the total kinetic energy, and the "forward" translational energy is 99.7%.

Second, the effect of angular velocity on terminal ballistics can be divided into two distinct cases: FMJ bullets, and expanding bullets.

In the first case, the mechanism by which FMJ bullets damage tissue is by de-stabilizing and tumbling. I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me. It seems logical that the more stable a bullet is when it enters tissue, the less likely it is that the bullet will begin tumbling immediately, but the difference may be negligible when impacting non-uniform tissue and bone.

In the second case with expanding bullets, I'll approximate the bullet as a cylinder. When it hits tissue, I assume that the bullet expands to twice its original diameter. I also assume a conservation of angular momentum. Here we see that the bullet loses 70% of its angular velocity upon expansion, and 75% of its rotational kinetic energy, simply due to the increase in its moment of inertia. The rotational kinetic energy goes from ~8 joules to ~2 joules. So not enough of an energy difference to do much work on the tissue by itself. In reality, angular momentum is not conserved, since the tissue applies a torque on the bullet in the form of drag force causing the bullet to slow down even more, and consequently the bullet applies a torque back on the tissue, causing the tissue to accelerate radially from the bullet's major axis.

The real difference in terminal effects between different twist rates is seen in the centrifugal force on the core and jacket of the bullet. Assuming the same 0.224" 80 gr bullet going 3000 fps, fired from an 8" twist barrel versus a 14" twist barrel. I'm also assuming the mass of the bullet is concentrated in the jacket, for simplicity (this leads to an inflated value for the centrifugal force on the jacket, compared to when the mass is distributed uniformly throughout the bullet's diameter). The bullet fired from the 8" twist barrel experiences 11,790 newtons of centrifugal force on the jacket, while the bullet from the 14" twist barrel only experiences 3,850 newtons, or about 1/3 of the force trying to rip the jacket apart. This is equivalent to about 2650 pounds of force on every point of the bullet jacket, versus 865 pounds. The additional force would have a significant effect in expanding and fragmenting the bullet, and depending on the design of the bullet, this could have a meaningful effect on tissue damage.

One more thing to add: with respect to interior ballistics, if instead of an 1:8" rate of twist we had 1:14", the rotational energy would go from 7.5 to 2.5 joules, or 0.3% of the total kinetic energy to 0.1%."
"Definitely Not".
Thanks for posting that Jordan.
Riflehunter;
Good evening once more sir, thanks for the reply and kind words it contained.

I see that I wrote "if not better, than more reliably" and meant to write then, but if that's my only typo then I'm doing quite well!

The other day I was listening to a YouTube video discussing the new 8.6 Blackout where they're using a 1:3 twist, so the boundaries are being pushed more every day it seems.

There has to be trade off such as mathman mentioned with some loss of velocity.

Since that thread I've played around a wee bit with this online projectile RPM calculator.

http://www.findnchoose.net/bullet_rpm_calculator.html

The slower bullet from the Swede was turning 69,316 rpm faster than the .277 bullet from the slower than usual twist .270 and perhaps that was the cause of the difference in tissue damage? Perhaps?

To be sure we were looking at carcasses so it wasn't like the bullets didn't work at all but we did see some differences and wondered what the cause might be.

I'll note that my late friend BobinNH was a firm believer in 1:9 .270 barrels and he used them a fair bit, so that's a good foundation.

When I was still fooling with buddy's B78 in .25-06 we never measured the twist and the only other .257" barrel I've played with to any extent has what I believe is a gain twist barrel made by a chap in Alberta years back. I'd have to measure it again, or better said attempt to do so to recall what I thought the final twist was nearer the muzzle.

With the bullet technology seemingly growing in leaps and bounds every year, I'd think that depending upon case capacity a least a little extra faster twist can't be a really bad thing.

Gentlemen such as my friend Jordan are able to explain the math and physics many times better than I'll ever be able to do for sure. My observations are that of a student only - perhaps a serious student, but still not someone with many answers, just a bunch of questions usually. grin

All the best and thanks again.

Dwayne
Jordan;
Good evening my friend, I hope the day was decent to you all on your side of the big hills.

I was happy to hear and see on the news that they're going to do a real Stampede again this year, I hope that it goes swimmingly and some of the businesses get a much needed financial boost.

Thanks for the post sir, I've read it twice and I "think" I'm starting to wrap my head around it all.

When we've chatted about this before, I believe I've said it's more what the greater rpm does to the projectile rather than the rotational energy difference.

Your post surely explains what the Swede did to thin jacketed bullets - coupled with the fairly deep grooves in the barrel it's a recipe for them to come unglued.

Someday it's my hope and prayer we get a coffee or a meal together Jordan. If you ever make it out west here and have the time, please feel free to drop by.

All the best and thanks again.

Dwayne
Originally Posted by BC30cal
Jordan;
Good evening my friend, I hope the day was decent to you all on your side of the big hills.

I was happy to hear and see on the news that they're going to do a real Stampede again this year, I hope that it goes swimmingly and some of the businesses get a much needed financial boost.

Thanks for the post sir, I've read it twice and I "think" I'm starting to wrap my head around it all.

When we've chatted about this before, I believe I've said it's more what the greater rpm does to the projectile rather than the rotational energy difference.

Your post surely explains what the Swede did to thin jacketed bullets - coupled with the fairly deep grooves in the barrel it's a recipe for them to come unglued.

Someday it's my hope and prayer we get a coffee or a meal together Jordan. If you ever make it out west here and have the time, please feel free to drop by.

All the best and thanks again.

Dwayne
Thanks, Dwayne! The same goes for you if you happen to be on this side of the hills.

Yes, I think youā€™re right about that. My sense is that itā€™s less about the ratio of rotational kinetic energy to translational kinetic energy, and more about what the angular velocity does to the bullet itself (as evidenced by some of the photos in this thread), which changes the way the translational kinetic energy gets transformed into mechanical work done on the tissue.
Originally Posted by Jordan Smith
Originally Posted by BC30cal
Jordan;
Good evening my friend, I hope the day was decent to you all on your side of the big hills.

I was happy to hear and see on the news that they're going to do a real Stampede again this year, I hope that it goes swimmingly and some of the businesses get a much needed financial boost.

Thanks for the post sir, I've read it twice and I "think" I'm starting to wrap my head around it all.

When we've chatted about this before, I believe I've said it's more what the greater rpm does to the projectile rather than the rotational energy difference.

Your post surely explains what the Swede did to thin jacketed bullets - coupled with the fairly deep grooves in the barrel it's a recipe for them to come unglued.

Someday it's my hope and prayer we get a coffee or a meal together Jordan. If you ever make it out west here and have the time, please feel free to drop by.

All the best and thanks again.

Dwayne
Thanks, Dwayne! The same goes for you if you happen to be on this side of the hills.

Yes, I think youā€™re right about that. My sense is that itā€™s less about the ratio of rotational kinetic energy to translational kinetic energy, and more about what the angular velocity does to the bullet itself (as evidenced by some of the photos in this thread), which changes the way the translational kinetic energy gets transformed into mechanical work done on the tissue.

This makes sense to me. The wound is proportional to the KE. Playing with twist, bullet, constructiom, etc is shaping that wound. In the case of fragmenting bullets for ex, faster twist shreds the bullet a little faster allowing for more energy transfer in shorter period (i.e. pop a ground squirrell). May or may not ā€œimproveā€ terminal effect depending on what you want to do just like any of the other variables involved

Lou
Originally Posted by Jordan Smith
Originally Posted by JohnBurns
Originally Posted by Jordan Smith
In a recent, very similar thread I discussed the physics involved and gave some calculated numbers. Maybe do a search for the thread.

I would say this thread is more about real world results than "calculated numbers".
crazy

I would say that physics with its models and results are more than a little relevant to understanding how things work, in the case of ballistics as much as anything.

Well then post a proven model.

Just sayin.
Originally Posted by Jordan Smith
Yes, I think youā€™re right about that. My sense is that itā€™s less about the ratio of rotational kinetic energy to translational kinetic energy, and more about what the angular velocity does to the bullet itself (as evidenced by some of the photos in this thread), which changes the way the translational kinetic energy gets transformed into mechanical work done on the tissue.

Your "sense" is pretty far from an actual proven model.

Just Sayin twice. wink

Obviously you are free to post guesses and "sense" but don't pretend you have a "model" that accurately predicts the terminal effect of twist rate.
Burnsy's got a hard-on for Physicists. It's hilarious.
Originally Posted by kingston
Burnsy's got a hard-on for Physicists. It's hilarious.

Not all of them.

Just the ones that don't know that laminar flow does not happen in terminal bullet performance. EVER.

Turbulent flow does happen in terminal bullet performance every single time.
Originally Posted by Jordan Smith
In the first case, the mechanism by which FMJ bullets damage tissue is by de-stabilizing and tumbling. I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.

He is litterally spouting pure Bull Schitt.

Just sayin.
Originally Posted by JohnBurns
Originally Posted by kingston
Burnsy's got a hard-on for Physicists. It's hilarious.

Not all of them.

Just the ones that don't know that laminar flow does not happen in terminal bullet performance. EVER.

Turbulent flow does happen in terminal bullet performance every single time.
Originally Posted by Jordan Smith
In the first case, the mechanism by which FMJ bullets damage tissue is by de-stabilizing and tumbling. I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.

He is litterally spouting pure Bull Schitt.

Just sayin.
Wrong again, not that I would expect anything different.

Keep pretending with Wikipedia as your guide, and talking about things you neither know nor understand. Your ankle-biting is becoming extremely predictable.
Originally Posted by JohnBurns
Originally Posted by kingston
Burnsy's got a hard-on for Physicists. It's hilarious.

Not all of them.

Just the ones that don't know that laminar flow does not happen in terminal bullet performance. EVER.

Turbulent flow does happen in terminal bullet performance every single time.
Originally Posted by Jordan Smith
In the first case, the mechanism by which FMJ bullets damage tissue is by de-stabilizing and tumbling. I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.

He is litterally spouting pure Bull Schitt.

Just sayin.


Whoa, slow down there, I'm still studying your earlier treatise on the economics of nuclear fission.
Originally Posted by kingston
Originally Posted by JohnBurns
Not all of them.
Just the ones that don't know that laminar flow does not happen in terminal bullet performance. EVER.
Turbulent flow does happen in terminal bullet performance every single time.
Originally Posted by Jordan Smith
In the first case, the mechanism by which FMJ bullets damage tissue is by de-stabilizing and tumbling. I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.
He is litterally spouting pure Bull Schitt.

Just sayin.
Whoa, slow down there, I'm still studying your earlier treatise on the economics of nuclear fission.

Don't forget I included Fusion.

Originally Posted by Jordan Smith
Wrong again, not that I would expect anything different.

Keep pretending with Wikipedia as your guide, and talking about things you neither know nor understand. Your ankle-biting is becoming extremely predictable.

Originally Posted by Jordan Smith
I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.

Feel free to explain to the class about laminar drag forces in tissue and how such laminar drag would styme your calculations.

If you have time explain how any laminar flow is "chaotic" when the defintion of laminar flow is a lack of chaos.

As I posted earlier it might be a better if we all kept to real world results and skipped the PHD guessing.
Originally Posted by kingston
Burnsy's got a hard-on for Physicists. It's hilarious.


Your be waaaaaay better off taking notes than flipping your lip. šŸ‘
Great posts Dwayne, I remember reading and rereading that post.

And yeah, my affliction with twist came from Bob as well. It worked for him. Works well for me too.
Originally Posted by JohnBurns
Feel free to explain to the class about laminar drag forces in tissue and how such laminar drag would styme your calculations.

If you have time explain how any laminar flow is "chaotic" when the defintion of laminar flow is a lack of chaos.

As I posted earlier it might be a better if we all kept to real world results and skipped the PHD guessing.
Everything in your post is wrong. I said nothing about "stymying" my calculations, I said I hadn't done any on that particular quantity. I also never said anything about chaotic behaviour of the fluid flow (English is hard. I get it. But the sentence was about the chaotic behaviour of the bullet).

It's your typical MO or gaslighting and twisting the truth to suit your agenda. It's a waste of time to try and teach someone who can't be taught. But I will give you a hint. You might want to re-think this statement:

Originally Posted by JohnBurns
laminar flow does not happen in terminal bullet performance. EVER.

You're right, it might be better if we all kept to the real world. Perhaps it would be better for you to stick to acting like an ankle-biting troll, instead of acting like a pretend physicist. But as usual, you'll carry on with this instead of doing something useful and meaningful. It's not a good use of my time to continue, so enjoy.
Originally Posted by Jordan Smith
Originally Posted by JohnBurns
Feel free to explain to the class about laminar drag forces in tissue and how such laminar drag would styme your calculations.

If you have time explain how any laminar flow is "chaotic" when the defintion of laminar flow is a lack of chaos.

As I posted earlier it might be a better if we all kept to real world results and skipped the PHD guessing.
Everything in your post is wrong. I said nothing about "stymying" my calculations, I said I hadn't done any on that particular quantity. I also never said anything about chaotic behaviour of the fluid flow (English is hard. I get it. But the sentence was about the chaotic behaviour of the bullet).

It's your typical MO or gaslighting and twisting the truth to suit your agenda. It's a waste of time to try and teach someone who can't be taught. But I will give you a hint. You might want to re-think this statement:

Originally Posted by JohnBurns
laminar flow does not happen in terminal bullet performance. EVER.

You're right, it might be better if we all kept to the real world. Perhaps it would be better for you to stick to acting like an ankle-biting troll, instead of acting like a pretend physicist. But as usual, you'll carry on with this instead of doing something useful and meaningful. It's not a good use of my time to continue, so enjoy.

LOL.

Word Salad.

Originally Posted by Jordan Smith
I haven't calculated the destabilization of the bullet due to the laminar drag of the tissue, but I suspect chaotic behaviour, so the effect of increased rotational speed isn't clear to me.
Originally Posted by Judman
Originally Posted by kingston
Burnsy's got a hard-on for Physicists. It's hilarious.


Your be waaaaaay better off taking notes than flipping your lip. šŸ‘

Setting aside any concerns for sounding too Burnsey, I'm one of those people who didn't have to take notes.

LOL
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