Twist Direction


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svtruth
May 11, 2011, 04:05 PM
Are there any reasons to have rifling twist one way or the other?

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rcmodel
May 11, 2011, 04:17 PM
Colt thought so.

They historically used left hand twist.
Just about everyone else used right hand twist.

One theory is that after the Colt factory burnt down, production was moved to England for a while and the English used left hand twist??

Another is that they used left hand twist to cause the recoiling gun to torque into the right handed shooters grip.

In actual fact, it makes no accuracy difference one way or the other on a rifle as far as I know.

rc

Standing Wolf
May 11, 2011, 04:44 PM
It's a secret. Even physicists and the president of the United States can't be trusted with it. Lee Harvey Oswald stumbled upon a small part of the truth, and you know what happened to him, right?

Trust me, please: you really don't want to know.

Cop Bob
May 11, 2011, 06:44 PM
It's a secret. Even physicists and the president of the United States can't be trusted with it. Lee Harvey Oswald stumbled upon a small part of the truth, and you know what happened to him, right?

Trust me, please: you really don't want to know.
That pretty much sums it up... and that's about all I have to say about that!

hirundo82
May 11, 2011, 07:51 PM
It's due to the Coriolis effect. Barrels made in the Northern Hemisphere have a right-hand twist, while those made in the Southern Hemisphere have a left-hand twist. Few people know that companies that make shotgun barrels have to locate their manufacturing facilities precisely on the equator to avoid having any twist to their barrels.

clancy12
May 11, 2011, 08:10 PM
Is this thread sarcasm central?

Manco
May 11, 2011, 08:40 PM
Is this thread sarcasm central?

No, not at all.

kingpin008
May 11, 2011, 08:46 PM
Well played, good sir. Well played. :D

JellyJar
May 11, 2011, 10:44 PM
Just to remember...If you can see what type of twist the rifling in a handgun's barrel has it is probably pointed right at you and you had better DUCK! :evil:

-eaux-
May 11, 2011, 11:50 PM
well i hate to be the one to step aside of the mickey mouse garbage and actually attempt to answer the OP's question, but...
the external ballistics of any handheld weapon that i know of could not possibly be measurably affected by whether the barrel is rifled RH or LH. i'm not standing upon any sort of scientific database here, but the external ballistics of a fired round, through a rifled barrel, can't possibly be altered that much by whether your toilet flushes clockwise or counterclockwise.

MachIVshooter
May 12, 2011, 09:16 AM
It's arbitrary, and has no effect on accuracy or recoil characteristics. The amount of torque generated by the rotating bullet is very miniscule, and spin drift occurs at range no matter which direction the bullet is rotating.

svtruth
May 12, 2011, 11:23 AM
Thanks all!
Very educational, as always.

NCsmitty
May 12, 2011, 01:49 PM
As http://en.wikipedia.org/wiki/External_ballistics indicates, RH twist barrels will spin drift (Gyroscopic drift) to the right, and LH twist will drift left.

Coriolis drift effect in the northern hemisphere makes the projectile appear to curve over to the right due to the earth's rotation.
So theoretically, a LH twist can offset the Coriolis effect in the northern hemisphere by some degree.

Long range artillery computations will take these effects into account, when plotting targets

Wikipedia doesn't always have it right, but can be a quick reference for many subjects, and usually understandable.



NCsmitty

Grey_Mana
May 12, 2011, 02:28 PM
A spinning ferromagentic object is going to create a magnetic field. Iron, cobalt, nickel, bismuth, ytrirrium, managanese, and a few heavy metals. Is there enough of any of these in your round to make a difference? If there is, the magnetic field will interact with the iron in your barrel. That interaction might have some infintesimal effect on trajectory.

Right hand twist = current in the direction the bullet is going.

KodiakBeer
May 12, 2011, 02:29 PM
If you're a reloader, you can just seat your bullets backwards if you have a gun with the wrong twist.

MachIVshooter
May 12, 2011, 05:06 PM
A spinning ferromagentic object is going to create a magnetic field

Most bullets do not contain ferrous metals.

Hypnogator
May 14, 2011, 01:10 PM
Early in my career in CID, agents were issued either a Colt Detective Special or a S&W Model 10 with 2" bbl. The Smith barrels were pinned in place, while the Colts weren't. Occasionally, some Colt users would experience shot groups that started to wander to the right, because the torque of the bullets being fired began unscrewing the barrels! :what::eek::uhoh:

The armorers were usually able to fix them handily, but I always preferred the slightly heftier Smiths. ;)

Zonie
May 14, 2011, 02:18 PM
It may have something to do with the machining capability of manufacturers. I don't know any specifics but it may be more convenient to machine a right hand twist than a left hand twist.

Interesting trivia- metric FAL flash hiders thread onto LH threads so that the force of the "spinning" gases behind the barrel force the flash hider on tighter, as opposed to loosen it.

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