Slow 30mm rounds from Apache

[Alan8325]

There are many videos online of the Apache's 30mm cannon in use, but I found this video showing it especially devastating and accurate. The 30mm rounds fired in this video look like they have very low velocity, more like 40mm grenades from a Mk19. Is this just an illusion? At least the cat got away!

http://shock.military.com/Shock/videos.do?displayContent=190518&page=1

[flamingknives]

Bear in mind that the Apache has high magnification on its sensors and the rounds are travelling almost directly in line with the cameras point of view.

Muzzle velocity of the M230 is about 800m/s, more than three times that of the Mk19, and maximum quoted effective range is 4000m (still more than 5 seconds flight time)

[MikeyD]

If you look at an Apache's 30mm cannon shell you'll notice they somewhat resemble oversize .45 bullets. A lot of projectile and not much shell casing. Apache rounds have considerably less muzzle velocity 'oomph' than a high-power 30mm Rarden round for instance (something you'll soon be able to compare).

Another thing to keep in mind, my own computer tends to *GASP* when an airborne gun run happens. The framerate just plummets. So you could be happily playing at 40fps then have it instantly drop to 9 fps in the two seconds that the shells rain down. Not only are the shells moving slow, so is everything else!

[Dietrich]

Reminds me of how in videos of tanks firing where the camera is more or less behind the tank, the shell seems to be travelling kinda slow, even though it's actually going 5,000 feet per second. But when you take into account the distance between the tank and its target -- an entire mile is well within effective range -- you can better appreciate the shell's extreme velocity, despite the distortion from the perspective.

[BlackMoria]

Based on the time from the sound of the cannon and sight shake to the rounds impacting, the range is between 3500 to 4000 meters, which is approaching the max range of the 30mm. At this range, the rounds are rapidly lossing steam and gravity is more a factor, which explains why the rounds seem to be coming in relatively slow (compared to the 805m / sec muzzle velocity as found for the apache 30mm cannon).

Edit: It is not a cat, it is a dog. You can see it wag its tail as the men approach and it relative size to the men makes it too large for the common cat. Nice to know the canine got clear.

[c3k]

The round-counter shows that each of the two bursts is 20 rounds (303 at start, to 283, then ending at 263).

Opening range seems to be 1450 meters; second burst starts at approximately 1200 meters.

Check the range icon on the left of the camera.

Regards,

Ken

[BlackMoria]

Odd that, as it doesn't square with what I am observing. The M230 chaingun has a published muzzle velocity of 805m/sec. From first sound of the gun and sight shake to the first impact is about 4.5 seconds. If the range on the HUD is correct, the impacts would be about 2 seconds to target.

[c3k]

Hmmm, 1300 ft. radar altitude (Height above ground), 80 knot airspeed, at beginning of engagement.

[c3k]

BlackMoria,

Your timing seems correct. The second burst, at 1200 down to 1100 meters, only takes roughly 3 seconds.

The issue would be the loss of velocity. If the muzzle velocity is 805m/s, what is the velocity at 1,000 meters?

At 1400 meters, I would say that the rounds fired had an AVERAGE velocity of 1400/4.5 = 311m/s

At, say, 1100 meters it is 1100/3=366m/s

Extrapolate the loss of 55m/s per 300 meters, round a bit, assume the loss in velocity is linear with regards to distance (I know, I know, but this is merely a rough, first order kind of calculation), and you get about 60m/s per 300 meters, or 20 m/s per 100 meters.

So, 11*20 ((1100 meters / 100 = 11) 20m/s per 100 meters range) is 220m/s increase as you reduce the range. 366+220=586m/s. Roughly on par with 805m/s. We're close.

Using the longer range number of 1400meters at 311m/s yields; 14*20=280 m/s increase.

311+280= 591 m/s.

Since we assumed a linear extrapolation from these two data points one would expect the two extrapolated values to correspond. They do.

Now, if we change the loss of velocity from a 1st order, linear, effect into a second order, squared effect, we should see some differences. It should result in a greater velocity as we get closer to the muzzle. Our data supports that.

I'll let someone else do the heavy lifting.

Regards,

Ken

[Sgt Joch]

Quite the fascinating video, both strangelly compelling and repellent since four lives are snuffed out in an instant. That 30 mm cannon is extremely effective...

They appear to have either not noticed or ignored the helicopter. Could it be so far away that they would not have heard it?

[Dietrich]

The body language of the now-late men in the video made me recall the almost stereotypical shot from pretty much any Western-military-glorifying movie in which the bad guys are striding along, oblivious to the Western über-technology taking aim at them, when said technology (be it tank, helo, or even just a plain ol' sniper rifle) opens fire and suddenly the bad guys all convulse dramatically and drop dead. But unlike in the movies -- where a single pistol-caliber round usually renders a bad guy dead before he hits the floor -- in this video the fire lays them all out (so to speak) and there's nothing unrealistic about it.

[JonS]

They appear to have either not noticed or ignored the helicopter. Could it be so far away that they would not have heard it?

Either that or helicopters buzzing about a km or more away are so common that nobody pays them any heed.

[McIvan]

Quite the fascinating video, both strangelly compelling and repellent since four lives are snuffed out in an instant. That 30 mm cannon is extremely effective...

You're only assuming their lives were snuffed out, as opposed to blown to the ground and maybe peppered with fragments. Obviously anyone who got a round directly is either dead or an amputee, but those not directly hit are not necessarily dead or even hit by anything.

It sure looks grim for them, but we've probably all read accounts of huge amounts of incoming that doesn't actually do much.....er, albeit that in that situation the people are usually under cover.

[Alan8325]

Quite the fascinating video, both strangelly compelling and repellent since four lives are snuffed out in an instant. That 30 mm cannon is extremely effective...

They appear to have either not noticed or ignored the helicopter. Could it be so far away that they would not have heard it?

Every time I see one of these videos the targets do not seem to be aware that they are being fired at until the first round impacts. Usually the spread of impacts is so wide that the enemy are able to scatter once the first round hits and the Apache gunner must then hunt them down one or two at a time. This video, however, shows some very accurate grouping that did not give anyone time to move an inch.