Topic: Right hand rifling?

[labcoptr]

Hi,
All dear collegues,
I wonder that Is there any scientific back round; why does all of the infantry rifle riflings right hand twist?

with my best regards

[Teresa Rutherford]

Scientific basis of this? I guess Physics could explain this but as far as I know, most people are right handed that's why rifles are being made for right-handed people in general. Left-handed people take a lot of time adjusting and well-versing this right hand rifling.

[Aaron Brudenell]

To the best of my knowledge, most guns are right hand twist but there's no practical advantage for small arms on the direction of twist.  I suspect if you're working with very large bore guns that fire great distances there may be an observable difference but it's likely to be very subtle.

[Justine Kreso]

The individual who posted originally was referring to the twist of a firearm--not the external design in reference to being right or left handed.  A

[Bob Hart]

Explanation #1 (traditional):

In a revolver with the cylinder swinging out to the left, the torque of the bullet engaging the right hand rifling forces the frame toward the cylinder, reducing the likelyhood of the cylinder opening unintentionally.  Colt, on the other hand, claimed that their left hand twist torqued the gun into the hand of a right handed shooter.  

Explanation #2 (alternate):

At the time rifling was introduced, existing lathes were usually set up to cut right hand screw threads.

Explanation #3 (my observation):

British Enfield rifles had left hand twist rifling.  Brits drive on the opposite side of the road.  Coincidence?

Bob

        

[Scott Doyle]

Can we make Bob's post a poll? 

I'll vote for number 2 and agree with number 3 in principle.

[Bob Shem]

I'd say #2 because if you want twist it has to go one way or the other.  Since "righty tighty" is pretty standard for screws and bolts etc it makes sense that someone followed that theme when they first starting cutting rifling.

Once started, why change?

As for #1, single-shot firearms with rifling certainly preceded swing-out revolvers, so that explanation doesn't make sense.  And, frankly I have never been able to discern the direction of rifling twist while shooting a firearm based on torque.

[Stojan Kostic]

My best guess is...
When the projectile travels through the barrel by moving in a clockwise direction (from left to right), the barrel rotates in the same manner (from left to right) viewed from the opposite direction of bullets motion. Since most of the barrel on the soldiers' rifles traditionally had right threaded connection with receiver, this prevents unscrew of barrel after a large number of shots fired.

[Nelson Welch]

me thinks some clarification is needed.   I do not use clockwise or counter-clockwise in talking about the rifling twist or spin of a bullet for the following reasons.
  
If you are the shooter, the bullet is going away from you and spinning to the right in a clockwise manner.
If you are being shot at, the bullet is coming towards you and spinning to the right in a counter-clockwise manner.

Also the speed of the the shot going away from you may be the same as the speed of the shot coming towards you but their VELOCITIES are sure different!  I would still like to see this difference between speed and velocity make it into our glossary.

I also think of looking at a clock from the front and from the back side.  From the front, the hands move clockwise and it may be 15 minutes before lunch time.  From the rear, the hands move counter-clockwise and it would be 15 minutes after lunch time.  The clock would keep perfect time with the hands moving either clockwise or counter-clockwise.  You just have to know which side of the clock you are on to be able to tell the correct time.

In button rifling the following would apply:
If the button is pulled from the muzzle end towards the breech, the rod attached to the button and the button would rotate counter-clockwise to produce a right hand twist. If the button is pulled from the breech end towards the muzzle, the rod attached to the button and the button would rotate counter-clockwise to produce a right hand twist.  When viewing the produced rifling from either the muzzle or breech, the lands and grooves would twist to the right clockwise.
 
take care.
nelson
And also some mornings I get up on the wrong side of the bed on purpose.

[Stojan Kostic]

I hope that this picture will clarify my opinion. Best regards Stojan

[Mike Barnes]

Here is a nice discussion on speed vs. velocity:
http://www.physicsclassroom.com/class/1dkin/u1l1d.cfm

[Nelson Welch]

Very good correct diagram Stojan Kostic!

However, make sure that the bullet spin and barrel rotation representations are to be used only for direction and not magnitude.  Because of Newton's third law the magnitudes would be equal.
Now lets put some numbers into the torque equation to see how big these things are.
Lets take a 280 grain bullet in .458 caliber.   280 grain is nice because 25 of em will make a pound.

So the torque equation is that torque = the cross product of r X F.  where r is the length of the lever arm or moment and F is the force. So r = .229 inches or 0.019083333 feet and if the entire 280 grain force were applied on the tangent of the bullet perpendicular to the longitudinal axis 280 grains = 0.04 lbs.  so  0.01908333 feet times 0.04 lbs. = 0.00076333 ft. lbs. of torque.  
No wonder Bob Shem can't feel this torque!!!!  

I have used a torque wrench in the past but never seen one that would measure something this small.

Now on this same .458 bullet, if the rate of twist is 1 revolution in 12 inches...  Then the rifling land edges would make an angle relative to the longitudinal axis of the bullet of 6.837352073 degrees.  
Now with this angle,,, we have to multiply the sine of this angle to the above calculated torque to get a more accurate idea of the true magnitude .. so 0.00076333 ft. lbs. times sine of 6.837352073 =  0.000090875 ft. lbs. of torque.  I am not sure that this torque on the barrel would keep it tight!!

take care..   nelson.

[Stojan Kostic]

Finally I managed to find spare time and made my own calculation. I’ve got different result. So let’s start…
More appropriate formula to calculate torque or moment of force M for solid body in revolution is:
M=I*dω /dt where I is bullet’s moment inertia, ω angular velocity, and t is time.   (1)
The value of I depends on geometric properties and mass distribution of bullet so it is not easy to calculate it. To do this anyway, we can approximate bullet with solid cylinder with exact diameter and mass. Moment inertia of solid cylinder is I=m*D^2/8 where m is mass and D is diameter of a bullet
Angular velocity ω=2*V*tan φ/D where V is speed of bullet into barrel, φ is constant rifling twist angle   (2)
Then dω/dt=2*tan φ/D*dV/dt   (3)
dV/dt=P/m*pi*D^2/4 where P is gas pressure into barrel   (4)
So from (1) to (4) and after some arrangement, we have for moment of force
M=pi*D^3*tan φ/16*P   (5)
And from (5) we have max M for max P so it will be Mmax=pi*D^3/16*tan φ*Pmax   (6)
Now it’s time to input all values into equation and we have:
D=0.458 in=0.0116 m
tan φ=pi*D/(12*0,0254)= 0,1196
Pmax=3700 bar=3700*10^5 Pa for 458 Win Mag
Mmax= pi*0.0116 m^3/16*0.1196*3700*10^5 Pa=13.5624 Nm=10 ft lbf   (7)
Well, my conclusion is, if my result is good, the torque on barrel produced by bullet spin cannot be neglected, although its value isn’t large.

Best regards, Stojan

[Nelson Welch]

Very nice Stojan!
The difference is that the posting I did on Jan.16 was for a static situation using weight and would only work on earth.
The explanations done by Stojan is for a dynamic situation using mass and would work not only on earth but mars, the moon or outer space.

Now, this brings up something I was taught early by my trainer when he said any expert in any field should never forget the three most important words that sometimes have to be used when testifing.  Most of you do not know Mike Kelty, but I consider it an honor to having trained under him and wish I had some of his knowledge.

Now back to the three most important words to be used in testifing and I have used them many times!
They are.. "I DON'T KNOW".

So thanks Mike Kelty , Stojan Kostic, Mike Barnes, Bob Shem, Scott Doyle and all others that share information on this forum!!

 take care.
nelson.
ps.. I know I can put a bullet between my thumb and finger, snap my finger and cause the bullet to spin faster than any spin caused by rifling from a barrel!

[Todd Garrison]

Resurrected this discussion thread after reading:
"RIGHT-HAND TWIST" comment in the Reader Blowback section of G&A Oct. 2014
submitted by a Physical Engineer
- Garrison