Shooting Illustrated.

Q: While on a recent cleaning binge of my .45 ACP pistols, I noticed that some of the barrels had a right-hand twist, while the majority had a left-hand twist. This got me wondering why that was and what the difference between the two may be.

A: Related to rifles at distances of 300 yards or farther, spin drift can become a factor that will affect the impact of the bullet on the target. Long-range shooters correct for spin drift in right-twist barrels by making windage adjustments to the left as the distance increases. It is just the opposite for left-twist barrels that require a windage adjustment to the right to keep the bullet impact centered on the target.

Further in that vein, it can be proven mathematically that one twist direction is better when used in the Northern Hemisphere and the other is better for use in the Southern Hemisphere in addition to benefits to countering the Coriolis effect on long-range precision shooting.

This may be so, but I have never met or heard of a shooter who put all that into practical application. Also, note that all of the above examples involve rifles, and most of the scientific explanations involve shooting at extreme ranges—the Coriolis effect is not going to have any measurable influence on accuracy with a handgun shooting a standard handgun round at realistic handgun ranges.

In reference to the .45 ACP specifically, I am aware of tests conducted by some of the military teams regarding twist rates and direction, in an attempt to wring the absolute maximum performance from their match guns. This effort was put forth to give their national-level shooters an edge over their counterparts. I am unaware of any discernible game-changing difference that would favor one twist direction over another. If any irrefutable evidence had come from these tests, there would have been a wholesale effort for change across the board. This did not happen.

It is speculated that when John Browning invented the 1911, he designed it as a right-handed pistol for the Cavalry Soldier who could handle the reins with the left hand and shoot with the right. The left twist in the barrel was designed to torque the gun into the palm of the right hand, lessening the likelihood of the Soldier losing control of the pistol during firing. This makes a lot of sense, but is unsupported by any evidence as far as I know.

I had never heard this about JMB’s design of the 1911, and it may be apocryphal.  But Browning was so meticulous and detailed that the decision would actually make sense.

I confess that I have never closely observed the rifling twist direction in my 1911s before, but you can bet your bottom dollar I’ll pay close attention the next time I do a cleaning.  I’ll also pay close attention to rifles as well.

This is an interesting question.