Lee 356-120-TC revisited

[John Van Gelder]

I submitted a post about this bullet some time ago and never got any responses. My initial question was if anyone had done any testing to see if this bullet would tumble once it got into some sort of medium. It is pretty common knowledge that the FMJ round nose bullets will pretty predictably tumble.

I had a little time and the weather was co-operating, I devised a test to answer my own question. My "scientific" test consisted of two one gallon milk jugs full of water and one cardboard box.

I put one jug in front of the box, with about 6" of gap, the second jug went inside of the box with about 6" of space between the jug and front and rear of the box. One jug out side the box and one inside.

Upon the shot there was lots of water in the air, a nice neat round hole in the box behind the first jug, both jugs were severely damaged, When I pieced them together the first jug appeared to have neat round holes, front and back, the second jug appeared to also have a neat round hole in the front, the back hole was irregular, and the exit hole from the box as a rectangle and not a round hole.

I think it's safe to say that this bullet does tumble, for my applications, shooting the occasional predator, that is a good thing. A tumbling bullet does more damage than one that bores straight through.

[Cast10]

I load this bullet for my Glock 9’s. Functions and shoots well. It is not used as a defensive or killing round at this time.

I have never wanted to see if any bullet tumbled upon impact, as that is an inconsistent result of lots of factors. As long as it ain’t tumbling going in the paper, I’m good.

Lots of bullet tumble, and for me, if they tumble once they’ve penetrated, so be it.

[justindad]

Another way to evaluate tumbling could be to check for keyholes in targets at long range. Wadcutters keyhole past 50 yards, and someone here once shared a video of wadcutters keyholing in gel. Tumbling is probably a result of instability. I imagine the twist rate of your barrel will also affect tumbling.
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That is just me hypothesizing, so take it with a grain of salt.

[John Van Gelder]

There is a lot of empirical data that indicates that flat point bullets tend to tumble less than the more "pointed" designs.
the "chaps" over at Ammoland did some pretty extensive testing with various calibers and bullet shapes and that was their conclusion. I like the TC Lee bullet because it will reliably feed in almost anything, and are a joy to use with speed loaders in .38/.357s. As far as the tumbling goes medium density is also a determining factor. I had a batch I made up of a particularly hard alloy, to check the penetration I fired them into a dry fir log of approximately 5" in diameter, the bullet passed completely through the log and 6" of loose dirt and came to rest up against a large rock. These were loads I had chronographed out of my Ruger 9mm at 1150-1200 fps.

[Dusty Bannister]

If the projectile hits at point of aim. If the projectile penetrates without turning to fragments. Why is tumbling a concern?

[John Van Gelder]

As long as the bullet is flying "true" tumbling is not a concern, but as I stated early in the thread, I was curious if this bullet would tumble in a medium. And again a tumbling bullet in a medium, such as tissue will do more damage.

[BJung]

My pennies worth (and you know pennies are worth less today than before). I think you are curious whether a 9-122 TC bullet will tumble and make better HD bullet. I think there is a formula to make your own gel using gel packs in the supermarket. As for tumbling you, can try those TC bullets you had cast and some with grooves filed into them four ways like a Lehigh bullet. The grooves should make turbulence or tumble as you are looking for. I never did this but it's what I'd do if I did.

[MT Gianni]

If this is the one with tumble grooves IME, it keyholes long before it arrives at a target. No experience with the conventional lubed version.

[mnewcomb59]

Tumbling and keyholing are different things. Keyholing is where the bullet is not aerodynamically stabilized, either from too slow of a twist rate for gyroscopic stability, or if the bullet skids on the riflings and does not spin up to the expected RPM for the velocity and rifling twist rate.

Tumbling is where the bullet is not hydrodynamically stabilized, such as a torpedo from a submarine or a boat. The torpedo has a frontal area that creates a splash that is larger than the torpedo. When a torpedo hits water, the nose shoots water away from the torpedo and it actually travels in an air bubble. A wide flat nose 75% meplat bullet creates a wider wound than the bullet because the nose acts like a torpedo in water. This wide wound, for example a 40 cal air bubble from a 357 bullet, allows the bullet to travel in a straight line. There is a point where the splash from the flat nose is NOT larger than the bullet, and that is where yawing happens because of drag on the sides of the bullet. At around 60% meplat the bullets tend to act like a blunt round nose and gently yaw from side to side without ever flipping over and tumbling all the way. This gentle yaw creates a larger wound channel and shorter penetration than a WFN that penetrates pencil straight.

At around 50% meplat the bullets will tumble reliably within a few inches of penetration. The original German 9mm bullet was a 123 truncated cone with a roughly .18 cal meplat and it was a reliable tumbler.

[Kosh75287]

If that's the case, can anyone imagine what a 215 gr. SAECO #58 would do in tissue?

[Shiloh]

Mine drops at sub .357. .356 boolits in the 9mm have some keyholes

Shiloh

[John Van Gelder]

Shooting under sized bullets will cause tumbling. As far as any further testing goes, I think I found the answer I was looking for.

mnewcomb59 I might take exception to the torpedo analogy, in modern submarines the tube is flooded, then high pressure air is applied to a piston the forces the water and torpedo out of the tube, with wire guided "fish" the motor starts about the time the torpedo leaves the tube, or it can swim out.
Not really a good bullet analogy since the torpedo is self propelled... During the cold war I served on two missile boats and one fast attack.

[mnewcomb59]

https://navalpost.com/a-gamechanger-...ating-torpedo/

Talking about a 1977 Soviet torpedo "The manner makes it special was achieved by a specially designed flat nose cone, which deflects water outwards and initiates the supercavitaiton bubble."

[John Van Gelder]

A most interesting article. My takeaway is that the technology is still underdevelopment, the correlation here would be more direct if we were talking about the "Gyrojet" projectile, which was self propelled. Comparing torpedos to bullets completely neglects the rotational velocity of the bullet around 60K rpm for standard velocity 9mm ammunition. Back in the sisties there were a number of articles published about the early issued ammunition for the M16, that was reported to have tumbling issues. At the end of the day what determins if a bullet is going to tumble or not is bullet design and rate of twist in the barrel. Another point of interest is the rate of twist for the 9mm, 1 in 9 or 10, while most other hand guns of 35 caliber have a twist of 1 in 16-18. S&W offered ther early M&P 9mm with a 1in 16 but discontinued that option. The closest comparison is the .38 Super that uses the same weight bullets as the 9mm has a 1 in 16 twist.

Is a bullet going to tumble, the only way to tell is to see the test results.

My interest in marine technology waned after 1972 when I went off to Alaska to be a policeman.