76mm at 12,000 fps

[Last Hussar]

Ever wanted to track a Sherman round in slo-mo?

Of course you have.

https://www.youtube.com/watch?v=xpJ8EoGmLuE

Also don't lay any bets on the Soviet 152mm v watermelons challenge.

(Sorry - I couldn't embed it)

[Steve J]

That is so cool! Thanks for sharing .

[Ithoriel]

Great find, thanks!

So, is the lesson from this that the Wehrmacht should have added melons, perhaps instead of Zimmerit, to their tanks to deflect 152mm shot? 

[paulr]

When I saw the title I though 12,000 ft per second - that's way too high

[Last Hussar]

Great find, thanks!

So, is the lesson from this that the Wehrmacht should have added melons, perhaps instead of Zimmerit, to their tanks to deflect 152mm shot? 

Leon - can you get the Pz IVs remodelled with melons?

[Leon]

Leon - can you get the Pz IVs remodelled with melons?

All over or just two on the front...?

[paulr]

 

[Lord Kermit of Birkenhead]

Leon - can you get the Pz IVs remodelled with melons?

Make em a tad sticky once hit.

[steve_holmes_11]

Two lessons here:

* If you plan on hiding behind the watermelon display - ensure they're at least 12 deep.

* Never combine a lab-coat with shorts.

[O Dinas Powys]

Two lessons here:

* If you plan on hiding behind the watermelon display - ensure they're at least 12 deep.

* Never combine a lab-coat with shorts.

ALWAYS combine a lab-coat with shorts: adds a frisson if intrigue to the lab in the summer months

[Kiwidave]

What I found interesting was the 76mm round see-sawing in flight - what would cause that?

The bow and aft waves were pretty cool too.

[Lord Kermit of Birkenhead]

What I found interesting was the 76mm round see-sawing in flight - what would cause that?

The bow and aft waves were pretty cool too.

It should fly virtually flat. I can only think poor manufacture of the round..

[steve_holmes_11]

What I found interesting was the 76mm round see-sawing in flight - what would cause that?

The bow and aft waves were pretty cool too.

I think that's pretty standard for most rifle rounds.
Alas I cannot locate a reference now so this is a quick summary from memory.

Bullets / shells shot form a rifle have an early period of instability, then a length of stable flight, followed by a final wobbly stage.


The projectile goes down the barrel "gun barrel" straight (Your mileage may vary if you've gone a while without a barrel change).

As it leaves the barrel it get's a kick known as "Lateral Jump" - the interaction of a recoiling barrel, escaping gas and the shell hitting the atmosphere.
This may knock the projectile slightly off its axis, without significantly affecting the direction of flight.

After a while, the spin of the projectile will line it up, and provide a period of steady flight.
Explosive rounds (having greater mass distributed toward their outside) are likely to stabliise more quickly.

Finally, everything slows down, and the the round starts to flutter again.
Sometimes incorrectly described as "tumbling", a different thing which occurs after an impact.


That steady flight in the middle is efficient, contributing to range an accuracy.
Gunsmiths can control many design features that reduce the length of the initial unstable stage.
This often makes the difference between a great and a poor gun.
Explains why simply elongating the barrel, or increasing the propellant charge doesn't always upgrade the performance of an older piece.

You can also imagine why rounds like APDS suffered accuracy issues, and why worn aryillery barrely produce "shorts".


The same three element flight can be observed in a spin passed Rugby ball, american football, or even a swinging cricket ball.

[Kiwidave]

Thanks Steve; very informative

[fred.]

Some very cool videos - thanks for sharing.

On the video I think they mentioned that the yaw of the 76mm shell was in part due to the age of the gun 'virtually an antique' I think was the phrase  used.

The deflection of the 152mm shell off the water melons was astonishing - as was the amount of dust and smoke from firing it

[Ithoriel]

Yes, if anyone was in any doubt as to why "shoot and scoot" was a thing that should help clear it up

[Westmarcher]

You can also imagine why rounds like APDS suffered accuracy issues, and why worn aryillery barrely produce "shorts".

Shades of Stanley Unwin ......  

Sorry, Steve. Couldn't resist it.  
Here's some footage where you can actually hear the "tumbling."

[Orcs]

The deflection of the 152mm shell off the  water melons was astonishing

I am easily deflected by nice melons.

[Last Hussar]

Ignoring Orcs...

I went looking for a video of a arrow flight for comparison. Found the same guys recreating Japanese legend

https://youtu.be/kuOEpC4u6Tg

[Wulf]

I went looking for a video of a arrow flight for comparison. Found the same guys recreating Japanese legend

One of the ways of testing the 'balance' of a bow/arrow combination is by shooting through a piece of paper & seeing how close to circular the hole is... not very, usually... There's a thing called the 'archer's paradox' - the arrow doesn't fly through the middle of the bow (well, in modern bows it can) but along the side of it, but the string does push the back end toward the middle. Result, the arrow is pushed at an increasing angle off to the left (usually, if you're right handed & using a Western bow) side. This is compensated for by the weight & therefore inertia of the arrow head, and the 'spine' or stiffness of the arrow. It's fun getting that balance...  The arrow whips back & forth a few times, often visibly, then sorts itself out, hopefully before it reaches the target. Shooting at very close ranges can result in arrows at very unexpected angles in the target!