Any Testing of Extreme Twist Rate Handguns/Ammo

[Middletown]

I am putting this in general Handgun because I am mostly asking about testing of viability and effectiveness for defensive uses with handguns. Both, semi and revolver handguns and maybe concealable or nightstand gun.

Everything I have read only addressed bullet stability and accuracy during flight and accuracy was the objective. “ABC’s of Reloading” devoted a section on the history in the 1800’s and the formulas developed that I think are at least somewhat in use today. ABC’s also divided ballistics into internal, external and terminal for its definitions.

As a re-loader using quality components and good firearms, making ammo more accurate than I am is something I can do. I have always been very interested in internal ballistics. Matching powder, bullet and firearm for desired velocity has always given the terminal ballistics I want for hunting and practice/target shooting.


Has there been any known research of increased or extreme twist rates and terminal ballistics? Any of this research results available?

I searched a couple times and never found what I was looking for.

To keep the math easy a bullet fired from a 1:16 twist rate and barrel exit velocity of 1000 fps the bullet is turning 45,000 rpm’s when it leaves the barrel. That sounds like a lot and maybe it is. More than once I have fired both handguns and rifles concentrating of if the torque was something I could notice and it wasn’t. The torque has to be there but mass of firearm, recoil and other things must overcome the perception.

 

[Riomouse911]

There are soooo many variables to your question it would take volumes to answer it all.

IMHO the biggest variables surround bullet construction, since handgun velocities (Outside of the rifle-rounds fired in 14" Contender/bolt guns and the .460 S&W ) are fairly slow compared to what most rifles can do. A few simple examples may be:

Too fast a twist + light bullet construction = bullet goes "poof" in flight. (Try a traditional 50 gr .220 Swift through a 1/8" twist and see if anything you shoot even makes it 100 yards)
Too long a bullet + too slow a twist = unstable bullet. (I believe Marlin sped up the twist in the .444 rifles to allow heavier .430 diameter bullets..but I may be wrong on that.)
Too fast a velocity + too hard or too soft a jacket or material (if mono-metal) + fast twist means the bullet won't get grabbed by the rifling and it'll strip out of the grooves and wont spin properly (The rationale behind "gain-twist rifling" in the .460 XVR I believe).

I think the bullet companies do a pretty good job optimizing the recommended twist rates for their bullets, and the gun makers do a good job finding a twist rate that works in the most applicable scenarios. This is especially true in the last few years in the rifle world where ELD bullets have become so popular.

But, one can always experiment if you have spare frames for handguns and the coin to buy custom barrels with custom twist rates to mount on them.

Stay safe.

 

[Middletown]

Rio, Appreciate your response and don't disagree. My question is has there been any testing and if the results are available.

Edit to add: Self Defense also is part of my question.

 

[Rod47]

I'm thinking military ordenance probably spent time investigating this years ago

 

[CapnMac]

Well, if we isolate the various vector maths, we can see some things.

The bullet is a fraction, in the range of a thousandth the mass of the barrel. And the barrel is what is imputing the rotation upon the bullet. Newton's Third must still be satisfied, physics cannot be denied. But, it will be through each "de-coupling" of the linkage. Which reduces the vectors.

So, let's give the barrel a mass of 1000 (imaginary) units. Let's assign the bullet a mas of 1 unit. To satisfy Newton the rotation of the bullet must be answered, but the ratio will be 1/1000 in our example (and we have not dealt with friction losses and non-contact losses, each of which reduce the imputed torque.) While we are at this mental exercise, the barrel is still obeying Newton's First, and will "resist" the torque, and at a ratio near 1000/1.

*The bullet, by way of it's windage and frictional coefficients, is busy resolving its 'debt' to Newton's Second by trying to maintain equilibrium.

Now, in reality, all this is happening while the much larger vector equation of recoil is going on, which is what keeps rotational torque an insignificant factor in felt recoil.

As, as already cogently pointed out above, materials science does set upper limits on how much rotation can be imputed upon a projectile. (There's some interesting laminar flow things where the airflow gets close to a state change as a combination of both velocity and rotation, but those are way beyond our discussion here--and my pitiful math skills.)

 

[Varminterror]

Math evolves in time - but as new understandings of systems not previously understood. However, simple math remains simple math. For all of time and until the end of time, 2 + 2 will equal 4. The math involved with determining the rate of spin (rpm) of a bullet traveling at a speed (fps) down a barrel with a given rifling twist (inches per rev) won’t change. The physics involved with determining spin stabilization and moment of inertia are known. Not much to evolve there. We might remain to evolve new solutions, numerical models, for external trajectory and internal combustion simulations with ever increasing accuracy to real-world behavior, but figuring out twist stabilization is pretty straight forward.

Of note, while you calculated 45,000rpm for the slow flying, slow twist revolver cartridge, many bottleneck rifle cartridges will be spinning 250-300,000 rpm. The correlation between moment and spin for stabilization is out there, and it works.

 

[Jim Watson]

Has there been any known research of increased or extreme twist rates and terminal ballistics? Any of this research results available?

Any? Yes, but it may not satisfy in the computer age.
The NRA found that the 14" twist Colt .38 Special would expand a hollowpoint measurably more than the 18.75" twist S&W. Enough to matter? They didn't say.

Most pistol twist rate work has gone toward accuracy, though.
Frex SIG would sell you a dedicated lead bullet barrel for your P210.
Stock barrel has Ol' Georg's Euro standard 10" twist. The lead bullet barrel is 20".
Slow twist for soft swaged bullets, maybe.
But then Jerry Keefer piloted and Clark is making a 10" twist barrel for the S&W M52 wadcutter gun.

 

[Middletown]

Any? Yes, but it may not satisfy in the computer age.
The NRA found that the 14" twist Colt .38 Special would expand a hollowpoint measurably more than the 18.75" twist S&W. Enough to matter? They didn't say.

Thanks Jim That is kinda what I was looking for. Actually Thanks! for all the replies they have all been thoughtful.

I ask this question with self defense and terminal performance in mind. There may be a point where accuracy would suffer so much that that would also be considered but I don't know where that would be.

A bullet constructed for extreme twist, say 1 in 3 twist at 1000 FPS would be rotating at 240,000 RPM's. I wonder how it would perform for heavy clothing, penetration and still expand. Changing the direction of the bullet if it hit bone would possible also matter under those situations. Also maybe increase soft tissue damage.

I guess our discussion would be speculation unless there was actual development and testing. I would be surprised If none of this has been tried at some point but if done maybe the results are not available.

Thanks again for the replies.

 

[Jim Watson]

There have been some strange things tried with rifles but I don't know of much in pistols.
I have a .223 with a 6.5" twist for 90 grain bullets. If I overload a Sierra 90 gr SMK enough to get to 1000 yards supersonic or even go full power with a 75 gr Amax, they don't always get to the target. Berger and JLK bullets would stand the velocity necessary to make it to 1000 yards supersonic.
The numbers said it should shoot as close to the wind as a 175 gr .308, but it wouldn't. A very fine 600 yard rig, though.

 

[PapaG]

There are soooo many variables to your question it would take volumes to answer it all.

IMHO the biggest variables surround bullet construction, since handgun velocities (Outside of the rifle-rounds fired in 14" Contender/bolt guns and the .460 S&W ) are fairly slow compared to what most rifles can do. A few simple examples may be:

Too fast a twist + light bullet construction = bullet goes "poof" in flight. (Try a traditional 50 gr .220 Swift through a 1/8" twist and see if anything you shoot even makes it 100 yards)
Too long a bullet + too slow a twist = unstable bullet. (I believe Marlin sped up the twist in the .444 rifles to allow heavier .430 diameter bullets..but I may be wrong on that.)
Too fast a velocity + too hard or too soft a jacket or material (if mono-metal) + fast twist means the bullet won't get grabbed by the rifling and it'll strip out of the grooves and wont spin properly (The rationale behind "gain-twist rifling" in the .460 XVR I believe).

I think the bullet companies do a pretty good job optimizing the recommended twist rates for their bullets, and the gun makers do a good job finding a twist rate that works in the most applicable scenarios. This is especially true in the last few years in the rifle world where ELD bullets have become so popular.

But, one can always experiment if you have spare frames for handguns and the coin to buy custom barrels with custom twist rates to mount on them.

Stay safe.

Way back in the late fifties dad and I loaded some of my Sisk hornet bullets in his 220 Swift cases. Glad we only did ten. They all blew up.

 

[Riomouse911]

Way back in the late fifties dad and I loaded some of my Sisk hornet bullets in his 220 Swift cases. Glad we only did ten. They all blew up.

Almost like you had loaded .220 Swift blanks...I can imagine the groundhog hearing the report in the distance and wondering why there wasn’t an exploding ‘hog nearby.

Stay safe.

 

[PzGren]

Twist rate can have an influence on terminal ballistics if the bullet can be stabilized for accuracy but the center of gravity is located to let the projectile tumble upon impact. This leads to a larger than calibre sized wound, basically what a JHP bullet does, yet a long projectile is required for that and wind drag will change, with a negative impact on longer ranges. This has mostly an effect on FMJs for military applications that need to conform with the Geneva Conventions.

Twist rate is optimized for barrel length, velocity and hardness of the projectile, respectively its jacket. When a projectile is forced into a very steep twist rate the friction is increased and with it comes a loss of velocity. ARs are a good example for the twist rate being adapted to bullet weight and barrel length and the Swiss SIG P210-5 had a standard twist rate of 1 in 10 inches while the lead barrel had a twist rate of 1 in 20.

 

[PapaG]

Almost like you had loaded .220 Swift blanks...I can imagine the groundhog hearing the report in the distance and wondering why there wasn’t an exploding ‘hog nearby.

Stay safe.

Never shot them at a hog. Couldn't hit paper and found shredded grass about fifteen yards ahead of where dad was lying prone trying to sight his rifle in.