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Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954421 11/10/17 05:48 PM
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Other factors are involved, such as shape (b.c.) and length of projectile, but it is still just basic physics. Think of throwing a ping-pong ball and a javelin. Both may leave at the same rate of speed, but distance traveled and maintained speed or rpm will vary. So many variables, grins. That is why there are twist calculators. Enter your b.c., velocity, and altitude and it will spit out an appropriate twist rate. Or just shot a Nosler Partition and kill stuff...grins. I would much rather have a "tough" bullet, than worry about impact RPM's and collateral damage.

Last edited by Texasteach; 11/10/17 05:49 PM.

You did what?
Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954424 11/10/17 05:51 PM
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No, I am grasping it quit capably.

You and most including myself until recently fail to grasp what the twist rate represents.

The twist rate literally measures the distance traveled per revolution of the bullet.

Again, the twist rate is a measurement of the distance it takes the bullet to make one complete revolution.

That measurement is independent of velocity, time, or rpm's which only measures revolutions in a minute.

RPM's measure revolutions per unit of time, independent of distance traveled.

A chainsaw can turn 10,000 rpm's without moving any distance at all.

The issue under discussion is how many revolutions of the bullet occur when the bullet travels through a deer. That can be answered knowing the twist rate of the bullet regardless of its velocity or rpm's. Changes in velocity will increase or decrease rpm's, but not the distance traveled by the bullet per revolution.

For the sake of discussion, please explain if a 308 175 grain bullet is going 3,000 fps fired from a 1:12" how many revolutions of the bullet occur in a distance of 12"?









Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954427 11/10/17 05:54 PM
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Jeff,

You are correct on the first. But your issue under discussion, there is no correlation. You fail to factor in resistance and the fact that the 1 in 9" is NOT a constant. I am out.

Last edited by Texasteach; 11/10/17 05:57 PM.

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Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954447 11/10/17 06:07 PM
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Jeff, everyone on this thread understands twist rates...we're trying to get you to understand (at your request) why a bullet fired from a barrel with a faster twist can cause more damage. Hell, I don't even hunt deer and I understand it! Out also. P_102.


Do not trifle in the affairs of dragons, for thou art crunchy and taste good with ketchup.
Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954503 11/10/17 06:53 PM
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P,

I “understood” it the same as all of comments until earlier this year, when I really focused on determining the specific question of how many revs actually occur inside the body of the deer. At first I was messing with velocity and rpm’s, then the answer was obvious and simple. It is very easy to conflate rpm’s into the actual number of revs, when they represent very different measurements in this context.

The factors that really matter for terminal performance are bullet design, velocity at impact, and what it hits. Some expand, some tumble, and some fragment, and some bullets do a combination of those performance factors. Impact velocity can make a major difference in terminal performance and bullet performance.

Twist rate influences bullet stability and may decrease or increase the likelihood of yaw and tumbling and fragmentation, so it potentially may matter with some designs and placements, but an extra 0.2 revs inside the cavity is not making a difference of significance.

Here is a slow twist, 1:12" 175 SMK at about 50 yards from earlier this week. This was a cull deer with a broken leg. The distance was about 40 - 50 yards walking almost straight away. He had a deformed antler I wanted to preserve for a euro mount, so a head shot was not an option. Since it was for the freezer, spine shots would have destroyed too much meat at this close distance. He was angled ever so slightly left, so put it down the left chest wall aiming to go behind the shoulder and hopefully not ruin the leg. He went about 15 - 20 yards. Any way, here is a slow twist with the 308 175 SMK's, which I keep reading "pencil through." The point of aim/intial impact is the back end of the rib cage and it plowed mostly straight forward and tumbled as the 175 tends to do.

Only a small portion of the leg meat was lost, the backstraps were untouched. wink






Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954510 11/10/17 07:12 PM
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Because you're still insisting on counting the number of revs inside the animal I have to believe that you still don't get it. Good hunting. P_102


Do not trifle in the affairs of dragons, for thou art crunchy and taste good with ketchup.
Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: P_102] #6954515 11/10/17 07:18 PM
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Originally Posted By: P_102
Because you're still insisting on counting the number of revs inside the animal I have to believe that you still don't get it. Good hunting. P_102


What the bullet is actually doing inside of the body is what matters for terminal performance.





Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6954537 11/10/17 07:38 PM
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All the faster twists are just to stabilize the longer heavier bullets. Jacket thickness and bullet construction is what determines the terminal effects. How many rpm's is meaningless.


One shot is all it should take.
Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: yotehater] #6954562 11/10/17 07:55 PM
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Originally Posted By: yotehater
All the faster twists are just to stabilize the longer heavier bullets. Jacket thickness and bullet construction is what determines the terminal effects. How many rpm's is meaningless.


Precisely. up

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: jeffbird] #6954591 11/10/17 08:32 PM
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Originally Posted By: jeffbird
Originally Posted By: yotehater
All the faster twists are just to stabilize the longer heavier bullets. Jacket thickness and bullet construction is what determines the terminal effects. How many rpm's is meaningless.


Precisely. up


I'm with these two^^^

Think about RPM, or revolutions per minute for a second. Even at 200,000 rpm that is only 3,333 revolutions per second. What is the flight time to a game animal? Assuming a muzzle velocity of 3000 fps (constant w/no decay) it only takes 0.1 second for the bullet to reach its target at 100 yards so that is only 333.3 revolutions. While 200,000+ rpm sounds like a lot there are no bullets that fly for anywhere near a minute therefore they achieve a much lower number. Maybe that makes sense to some maybe not, but I completely do not buy into faster twist rates causing a measurable amount of damage more than slower.


It's hell eatin em live
Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: ChadTRG42] #6954875 11/11/17 12:39 AM
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Originally Posted By: ChadTRG42
Since an AR already loses 100 fps compared to a bolt gun, I'd go faster twist than what you need. Most 140 grain will work fine in a 1:10" twist. But it wouldn't work well for the 162-168 grain bullets as good. It would handicap the rifle some. I would lean heavily to a 1:9" twist. Plus the faster twist helps with better terminal performance.

I went 1:11" twist on my 300 WM since it was "just enough". I now wish I had gone with a 1:10" to fully stabilize the heavy 30 cal bullets.


Not really interested in the larger weight bullets, so this sounds good so far. I know I'm losing some FPS, but I've been wanting an AR308 for years.

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: kmon11] #6954878 11/11/17 12:41 AM
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Originally Posted By: kmon1
First rifles Remington chambered in it were for 140gr bullets and had a 1:9.25 twist, have one in the safe. What barrel length are you planning on running?

If buying a barrel for one today I would go 1:9 or what ever the Berger twist rate calculator shows would run 162gr bullets. Just making sure to have other options in bullet weight.


Plan on 20-22". Not really going to be hauling this things around too much, so I would like the speed gain from a longer barrel.

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955595 11/11/17 05:19 PM
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(2) revolutions,inside a Deer?!?

Oh I'm CRYING...I'm laughing so hard!!!.............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955603 11/11/17 05:24 PM
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Originally Posted By: tenyearsgone
I'm getting back into this project, and need a barrel for my AR-308. It seems like splitting hairs with these twists though. I would like to use 140 grain bullets, and will reload.



My 22" Lilja 1-10" SALAMI 7-08,will stabilize 162A-Max at low tide,when freezing,if only as a matter of fact...mainly because it is a fact.

Throat,Twist and COAL determines what you can and can not shoot,as stability and housing same goes. A chambering can simply be no better than it's bullet and bullets matter wayyyyyyyyyyy more than head stamps. Now the only way bullets get better(BC increase),is to get longer,which requires more RPM and more COAL latitude.

I'd not build a 7-08 slower than 9",if only because I've got 'em in all twist rates cited. I also wouldn't build a 7-08 on a '10 Krunchenticker,due COAL latitude. I'd go Kreedmire all the way,because it'll shoot softer,jump to lands less and will outperform same. Doubly so,when talking an idea as poor as slummin' .284" 140's in a Self Shucker.

Hint...............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955876 11/11/17 08:57 PM
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Ok Larry, if a barrel has 1:9” twist how many revolutions will the bullet make in 18” of distance traveled?

Do agree 1:9” is the way to go for 7mm as been through five of them. They handle 140’s - 180’s and all in between.


Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955878 11/11/17 08:59 PM
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You are fixated on Fluff,which has no bearing,as to how gross RPM is both measured and interacts upon Victims.

I realize that you are doing your best however and that is the ONLY reason it is funny.

Hint..............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955898 11/11/17 09:08 PM
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No, the initial issue was argued by others that 1:9” is deadlier than 1:10” all else remaining the same. My point is that 1” faster twist is of no significance in terminal effect.

Since you were laughing and crying at the fact the bullet only makes 2 revs in 18”, please regale us with the calcs from the Coos Bay High math department.

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955902 11/11/17 09:10 PM
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Sweetheart...the barrel don't pass through a Critter and upon impact,the lineal velocity is MUCH different from it's gross RPM,so they do not track in sync.

Hint.

Who chews your food for you?..............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955905 11/11/17 09:13 PM
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You can’t calc an answer?



confused2

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955908 11/11/17 09:15 PM
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I assume your Mom?

Bless your heart............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955920 11/11/17 09:22 PM
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The bullet will conform to the rate of twist as long as it's in the barrel. As soon as it's in flight, it begins to shed velocity. Rotational velocity will decay also, but not nearly as fast as the bullet's forward displacement velocity decays. It won't work out to revolutions per distance traveled because of the velocity loss. It would work out to revolutions per time of flight, minus the rotational velocity loss...and ultimately is a waste of effort in the end.


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Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: Busheler] #6955921 11/11/17 09:23 PM
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Originally Posted By: Busheler
I assume your Mom?

Bless your heart............

Just one question.....do you spit or swallow....everyone can clearly see what you are......on you knees as much as kaepernick.... confused2

Just curious since you are clearly the smartest man in you own mind.....like to hear how the "expert" does it....I'm guessing you swallow....


Originally Posted by Sneaky
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Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: tenyearsgone] #6955925 11/11/17 09:25 PM
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Surely they taught math at Coos Bay High, right?

Still no answer?

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: RiverRider] #6955927 11/11/17 09:27 PM
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Originally Posted By: RiverRider
The bullet will conform to the rate of twist as long as it's in the barrel. As soon as it's in flight, it begins to shed velocity. Rotational velocity will decay also, but not nearly as fast as the bullet's forward displacement velocity decays. It won't work out to revolutions per distance traveled because of the velocity loss. It would work out to revolutions per time of flight, minus the rotational velocity loss...and ultimately is a waste of effort in the end.



Well looky there...someone shoots a bit.(grin)

By GOD,there's hope!..............

Re: 1:'9 1:9.5 or 1:10 twist for 7mm-08? [Re: SnakeWrangler] #6955930 11/11/17 09:28 PM
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Originally Posted By: SnakeWrangler
Originally Posted By: Busheler
I assume your Mom?

Bless your heart............

Just one question.....do you spit or swallow....everyone can clearly see what you are......on you knees as much as kaepernick.... confused2

Just curious since you are clearly the smartest man in you own mind.....like to hear how the "expert" does it....I'm guessing you swallow....




Weren't my intent to horn you up and there really wasn't a need to make a show outta coming out of the closet...it weren't no "secret". Hint.

No slighting your taste in men though. Pun be intended.

Hint.............

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