Rotational velocity vs wound severity

[winmag]

What if you throw in a gain twist barrel.....? There's a monkey wrench

Looking forward to seeing a baseline, & results of your testing.

 

[elkaholic]

What if you throw in a gain twist barrel.....? There's a monkey wrench

Looking forward to seeing a baseline, & results of your testing.

That's a good one. Seriously though, the rotation is still whatever the velocity x twist is as the bullet leaves the barrel......Rich

 

[winmag]

That's a good one. Seriously though, the rotation is still whatever the velocity x twist is as the bullet leaves the barrel......Rich

Very true for rpm.

However "IF" a tight twist tends to grind up lighter/shorter bullets, & a gain twist can sometimes "Ease" or "Aleviate" the grinding effects but still have a faster rpm at exit, there may be some Merritt to the jacket stress vs twist ratio. Hmmmm sounds too scientific not to be a monkey wrench hahahaha

This is like rocket surgery... I love it

 

[elkaholic]

Very true for rpm.

However "IF" a tight twist tends to grind up lighter/shorter bullets, & a gain twist can sometimes "Ease" or "Aleviate" the grinding effects but still have a faster rpm at exit, there may be some Merritt to the jacket stress vs twist ratio. Hmmmm sounds too scientific not to be a monkey wrench hahahaha

This is like rocket surgery... I love it

But gain twist also makes larger grooves in the jacket by virtue of the fact that that the angle changes as the bulllet progresses, which causes GREATER loss of jacket integrity........Rich

 

[Joe King]

The modified Point mass trajectory calc. includes rpm. It's neither linear or constant but the rpm loss seems to be about 20% over a 100yrds for a 168gr 7mm

JBM - Calculations - Modified Point Mass Trajectory

click on the link and then hit calc at the bottom

 

[elkaholic]

The modified Point mass trajectory calc. includes rpm. It's neither linear or constant but the rpm loss seems to be about 20% over a 100yrds for a 168gr 7mm

JBM - Calculations - Modified Point Mass Trajectory

click on the link and then hit calc at the bottom

I'm only seeing about 2.3 % ??

 

[Joe King]

1000yrd rpm-166249
Muzzle rpm-212793

166249/212793=0.781

1 - 0.781=0.219

100%*0.219 =21.9%

 

[elkaholic]

1000yrd rpm-166249
Muzzle rpm-212793

166249/212793=0.781

1 - 0.781=0.219

100%*0.219 =21.9%

That I'll buy! Your first post said 100 yards

 

[Joe King]

That I'll buy! Your first post said 100 yards

the other zero was implied

 

[elkaholic]

the other zero was implied

I knew that Joe

 

[Pdvdh]

I just located the article written by Adam S. Gubar entitled (terminal ballistics- getting past the bs) It was under (hunting bullet terminal ballistics)

Rich,

Does this article speak to bullet twist rate effects on bullet expansion and wound channel?

 

[elkaholic]

Rich,

Does this article speak to bullet twist rate effects on bullet expansion and wound channel?

He only touches on it but it is a good article. I think he only made one small comment that "the rotation tends to tear the flesh", or something like that. The percentage of energy of rotation vs forward momentum is small, but it still seems to me that a couple hundred foot lbs. exerted on a torn jacket would still be enough to cause more expansion with the jagged edges encountering flesh. For example, my 17 HMR only has 300 ft. lbs. of energy (at the muzzle) but those jackets easily come apart at 200 yards. This of course isn't apples for apples, but I think is an indicator. I don't know when I'll get a chance to test this theory? It may be down the road a bit. I really wish that I could locate the old article (with pics) of the 16 twist 30 carbine vs the 10 twist '06 both with 110's.......Rich

 

[Pdvdh]

So I researched a bit using Google and came up with one interesting Thread with one particularly interesting post. It would appear that little documented research has been conducted on this topic. I suspect the military has done some research, but their research is probably done with non-expanding bullets, which has little application for the hunting of game animals.

Here's a link to the article: Has there ever been studys done on twist rate vrs bullet terminal damage ??? - The Firing Line Forums

And here's the Post within the article that seems to have the greatest potential for expressing some valid information, based on the references cited in the post, the number of posts from this forum member, and the quality of the presentation of the information:

June 24, 2010, 01:41 PM Post #14
Scorch
Senior Member

Join Date: February 13, 2006
Location: Washington state
Posts: 10,408

There are an awful lot of people's opinions, "thinking", and "reasoning" here, and very little actual data. Very little scientific research has been done on the subject, as far as I know.

As far as non-scientific research, I actually knew and spoke at great length with a man who did quite a bit of testing on this subject back in the 1950s. He was a wildcatter and gunsmith who worked very closely with the Juenke brothers of Saturn Guns fame, as well as PO Ackley, Frank Barnes (who wrote COTW), and other well-known gun gurus, and who mentored Wes Ugalde (of TCU fame). This data was gathered by shooting animals, not paper, and was based on shooting hundreds of animals, not just one or two. IIRC, he experimented with 30-06, 270, 308, 7mm-06, 243 Win, 230 Ackley (80 gr .228" bullet on an -06 case), 22-caliber wildcats, and a few 17 caliber wildcats, using Nosler Partitions and hand-swaged bullets. His experience indicated that a higher rate of twist gave deeper penetration and considerably higher damage than slower rates of twist, but required better built and heavier bullets than factory bullets to really shine. Higher rates of twist gave deeper penetration (which always seems better than less penetration), longer wound channels (which seems better than short wound channels), and a very high percentage of 1-shot kills.

This is consistent with a lot of folk knowledge, including Roy Weatherby's claims of outlandish performance for his rifles (257 Weatherby and 300 Weatherby in particular), PO Ackley's claims of terminal ballistics, Mashburn's cartridge development, and Warren Page's work. It also is supported by the killing abilities of seemingly underpowered rounds that killed out of proportion to their paper credentials, like 22 Savage High Power, 6.5X54mm MS, and 7X57, which had higher rates of twist than needed launching heavier bullets than we would normally use here in the USA.
__________________

 

[elkaholic]

So I researched a bit using Google and came up with one interesting Thread with one particularly interesting post. It would appear that little documented research has been conducted on this topic. I suspect the military has done some research, but their research is probably done with non-expanding bullets, which has little application for the hunting of game animals.

Here's a link to the article: Has there ever been studys done on twist rate vrs bullet terminal damage ??? - The Firing Line Forums

And here's the Post within the article that seems to have the greatest potential for expressing some valid information, based on the references cited in the post, the number of posts from this forum member, and the quality of the presentation of the information:

June 24, 2010, 01:41 PM Post #14
Scorch
Senior Member

Join Date: February 13, 2006
Location: Washington state
Posts: 10,408

There are an awful lot of people's opinions, "thinking", and "reasoning" here, and very little actual data. Very little scientific research has been done on the subject, as far as I know.

As far as non-scientific research, I actually knew and spoke at great length with a man who did quite a bit of testing on this subject back in the 1950s. He was a wildcatter and gunsmith who worked very closely with the Juenke brothers of Saturn Guns fame, as well as PO Ackley, Frank Barnes (who wrote COTW), and other well-known gun gurus, and who mentored Wes Ugalde (of TCU fame). This data was gathered by shooting animals, not paper, and was based on shooting hundreds of animals, not just one or two. IIRC, he experimented with 30-06, 270, 308, 7mm-06, 243 Win, 230 Ackley (80 gr .228" bullet on an -06 case), 22-caliber wildcats, and a few 17 caliber wildcats, using Nosler Partitions and hand-swaged bullets. His experience indicated that a higher rate of twist gave deeper penetration and considerably higher damage than slower rates of twist, but required better built and heavier bullets than factory bullets to really shine. Higher rates of twist gave deeper penetration (which always seems better than less penetration), longer wound channels (which seems better than short wound channels), and a very high percentage of 1-shot kills.

This is consistent with a lot of folk knowledge, including Roy Weatherby's claims of outlandish performance for his rifles (257 Weatherby and 300 Weatherby in particular), PO Ackley's claims of terminal ballistics, Mashburn's cartridge development, and Warren Page's work. It also is supported by the killing abilities of seemingly underpowered rounds that killed out of proportion to their paper credentials, like 22 Savage High Power, 6.5X54mm MS, and 7X57, which had higher rates of twist than needed launching heavier bullets than we would normally use here in the USA.
__________________

You could also throw the 6.5 Sweede in the mix. For years claims have been made that the 7 1/2 twist rifle did damage beyond its size.....Rich