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Posted: 1/3/2006 6:41:06 PM EDT
I read an article where the author touted a 1x12" twist barrel as being the most accurate he had ever shot? If this is true, why are most barrels 1x9"?
Link Posted: 1/3/2006 6:45:46 PM EDT
[Last Edit: 1/3/2006 6:48:06 PM EDT by theshootersden]
The rate of twist determines the optimum bullet weight/length for a given caliber and speed of the bullet by applying the proper spin on the bullet to prevent the bullet form yawing and pitching... Expressed in terms of the number of revolutions per inch of barrel length, this ratio is commonly expressed by designations such as 1:9, 1/9 or 1 in 9 twist, the 1 represents 1 twist, the 9 represents inches of barrel length... A good rule of thumb is that the heavier, or "longer" a bullet is, the faster the twist rate needs to be to stabilize it in flight, therefore a lighter "shorter" bullet needs a slower twist rate to give proper bullet spin for correct flight... Over stabilization of bullets can occur when larger heavier bullets in a given caliber are fired at very high velocities...

In general for the .224:
1/7 Good twist for the 50-100 grain bullets. Excellent accuracy with 60 grain bullets and up...
1/8 Good twist for the 50-80 grain bullets. Excellent accuracy with 55 grain bullets and up...
1/9 Good all around twist ratio. Will shoot well with bullets anywhere from 40-75 grains in weight...
1/10 Good twist for the 40-62 grain bullets, but favoring the lighter side a little more...
1/12 Good twist for the 40-55 grain bullets...
1/14 Good twist for the 40-45 grain bullets...

You can use the Greenhill formula to determine the proper bullet to twist ratio... It is based on the rule that the twist required in calibers equals 150 divided by the length of the bullet in calibers...

This can be simplified to:
Twist = 150 X D2/L (D2 = D squared)
Where:
D = bullet diameter in inches
L= bullet length in inches
150 = a constant

This formula had limitations, but worked well up to and in the vicinity of about 1,800 f.p.s. For higher velocities most ballistic experts suggest substituting 180 for 150 in the formula...
Link Posted: 1/3/2006 7:51:10 PM EDT
Now THAT has got to be the best explanation of barrel twist rates I have ever read
Link Posted: 1/3/2006 8:00:01 PM EDT
[Last Edit: 1/3/2006 8:01:40 PM EDT by MyakkaVice]
Without a doubt that is the most indepth answer I have ever gotten on this board. Thank You! I'm going to print that out for reference.
Link Posted: 1/3/2006 8:10:22 PM EDT

Originally Posted By theshootersden:

1/9 Good all around twist ratio. Will shoot well with bullets anywhere from 40-75 grains in weight...




HOLD ON THERE!


There are a few 1/9 barrels that will stabilize a 75 grain bullet but there are a LOT that won't and will end up key-holing the bullet.

There are even warnings on some boxes of that ammo saying to use 1/8 or faster twist.

1/8 or 1/7 is the best twist for 75 grain bullets.

IMO 1/7 is the best all around unless you plan on shooting 40 grain bullets, which are useless for defensive purposes.
Link Posted: 1/4/2006 8:54:50 AM EDT
[Last Edit: 1/4/2006 8:57:02 AM EDT by theshootersden]

Originally Posted By ALPHA9000:

HOLD ON THERE!

There are a few 1/9 barrels that will stabilize a 75 grain bullet but there are a LOT that won't and will end up key-holing the bullet.

There are even warnings on some boxes of that ammo saying to use 1/8 or faster twist.

1/8 or 1/7 is the best twist for 75 grain bullets.



You are correct about one thing, "1/8 or 1/7 is the best twist for 75 grain bullets."

I didn't say 1/9 twist was the best for the 75 grain .224 bullet, I said it would shoot well with the 1/9 twist barrel...

I have yet to see ANY true 1/9 twist barrel not handle ANY .224 caliber 75 grain bullet...

Check out the link below...

www.bushmaster.com/le/tests/hornady_tactical_ammunition.htm
Link Posted: 1/4/2006 9:31:52 AM EDT

Originally Posted By theshootersden:

Originally Posted By ALPHA9000:

HOLD ON THERE!

There are a few 1/9 barrels that will stabilize a 75 grain bullet but there are a LOT that won't and will end up key-holing the bullet.

There are even warnings on some boxes of that ammo saying to use 1/8 or faster twist.

1/8 or 1/7 is the best twist for 75 grain bullets.



You are correct about one thing, "1/8 or 1/7 is the best twist for 75 grain bullets."

I didn't say 1/9 twist was the best for the 75 grain .224 bullet, I said it would shoot well with the 1/9 twist barrel...

I have yet to see ANY true 1/9 twist barrel not handle ANY .224 caliber 75 grain bullet...

Check out the link below...

www.bushmaster.com/le/tests/hornady_tactical_ammunition.htm



That is one example, just one.

I even saw pics not too long ago posted around here where they were keyholing out of a person's 1/9" barrel.

There are so many damn threads that I can't find the pics, but it is common knowledge around here that 1/9" barrels are not reccomended for 75 grain bullets and it is to be taken on a case by case basis.

There is a reason why the 1/7" twist barrels are getting popular.
Link Posted: 1/4/2006 9:39:51 AM EDT
[Last Edit: 1/4/2006 9:49:30 AM EDT by theshootersden]

Originally Posted By ALPHA9000:

That is one example, just one.

I even saw pics not too long ago posted around here where they were keyholing out of a person's 1/9" barrel. That is one example, just one.

There are so many damn threads that I can't find the pics, but it is common knowledge around here that 1/9" barrels are not reccomended for 75 grain bullets and it is to be taken on a case by case basis.

There is a reason why the 1/7" twist barrels are getting popular.



"That is one example, just one." LOL...

To bad you dont live near me because I would be able to show you several examples...

And the "reason why the 1/7" twist barrels are getting popular" is because the worlds super power military is using them...
Link Posted: 1/4/2006 11:06:12 AM EDT

Originally Posted By sic_ness:
Now THAT has got to be the best explanation of barrel twist rates I have ever read



+1
Link Posted: 1/4/2006 2:03:48 PM EDT
I was just going to ask that same question.

Thanks for a great explanation..
Link Posted: 1/4/2006 2:36:42 PM EDT

Originally Posted By theshootersden:

Originally Posted By ALPHA9000:

That is one example, just one.

I even saw pics not too long ago posted around here where they were keyholing out of a person's 1/9" barrel. That is one example, just one.

There are so many damn threads that I can't find the pics, but it is common knowledge around here that 1/9" barrels are not reccomended for 75 grain bullets and it is to be taken on a case by case basis.

There is a reason why the 1/7" twist barrels are getting popular.



"That is one example, just one." LOL...

To bad you dont live near me because I would be able to show you several examples...

And the "reason why the 1/7" twist barrels are getting popular" is because the worlds super power military is using them...



Listen buddy, not everyone's 1/9 barrel will fire those 75 grain bullets without keyholing. This is the reason to go with the 1/7 barrels.

Your reason why people want the 1/7 barrels is an opinion, and in my opinion is wrong.
Link Posted: 1/4/2006 2:51:32 PM EDT
[Last Edit: 1/4/2006 3:14:00 PM EDT by theshootersden]

Originally Posted By ALPHA9000:

Listen buddy, not everyone's 1/9 barrel will fire those 75 grain bullets without keyholing. This is the reason to go with the 1/7 barrels.

Your reason why people want the 1/7 barrels is an opinion, and in my opinion is wrong.



I'm not wasting anymore of my time with your "I read, or I was told so" theories... I'm stating facts that I have myself done and others that Ive trained with have done...

Lastly, A true 1/9 twist, quality barrel, will be able to handle up to a 75 grain bullet without any significant problems... Believe it or not is your choice... Try it some time and you will see for your self...
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