LATAM Airlines finds bullet hole in B767
at what point the projectile goes transonic (and starts to tumble)
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In ancient times, when I was in basic training in the German army, we learned the safety distance for a G3 (7.52x51) was 3000m, the effective combat range of the same gun when mounted was 900m.
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In ancient times, when I was in basic training in the German army, we learned the safety distance for a G3 (7.52x51) was 3000m, the effective combat range of the same gun when mounted was 900m.
I don't know at what point the projectile goes transonic (and starts to tumble), but I guess it's probably at 2000+ m.
I heard the AK47 has a somewhat shorter barrel, so the bullets should be a bit slower, but they still should reach up a few thousand feet.
I don't know at what point the projectile goes transonic (and starts to tumble), but I guess it's probably at 2000+ m.
I heard the AK47 has a somewhat shorter barrel, so the bullets should be a bit slower, but they still should reach up a few thousand feet.
In broad terms, the AK has both a lower muzzle velocity (approx 2350ish ft/s versus approx 2700ish ft/s) and less energy (approx 2000 ft-lb-ish versus approx 2500 ft-lb-ish.) than a typical 7.62 x 51 caliber firearm. The rate at which velocity and energy will degrade is significantly affected by the ballistic path.
It was generally assumed that at 1,500 you were safe from AK.
Well, that's the 'effective' range..... but you'd still want to keep your head down at double that.
Well, that's the 'effective' range..... but you'd still want to keep your head down at double that.
Photo is of a nav light flasher relay that took an AK round when we were either on the ground or low flying. Penetrated the outer skin of thin aluminium before impacting. Round came to rest in the relay with a mushroomed head. Range indeterminate, never even heard the shot.
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Gravity
Originally Posted by ritam
I'm guessing your training involved projectiles travelling in a mostly horizontal direction. In a vertical shot, gravity is acting directly against the direction of travel, which means the downward acceleration of gravity is 100% against the direction of the forward momentum.
The bullet leaves the barrel at about 700m/s. It gets slowed down by gravity by about 10m/s^2.
Assuming the bullet is travelling straight up and has no air resistance, it passes through 1500m (~4500ft) a bit over two seconds later, still doing slightly less than 680m/s.
Since the bullets usually don't reach much further up, I guess gravity effects can mostly be ignored.
Or did I miscalculate somewhere?
Assuming no air resistance isn't a very safe assumption. If you just consider gravity, the bullet would reach about 24,000 meters. . .
But I guess that in itself demonstrates that gravity plays a relatively small role in slowing a bullet fired vertically. In fact, if you assume that the bullet's velocity is zero at 1500m, and slows at a linear rate, gravity would act on it for 4 seconds instead of two, and account for the loss of 40 M/S instead of 20. Still pretty small potatoes.
But I guess that in itself demonstrates that gravity plays a relatively small role in slowing a bullet fired vertically. In fact, if you assume that the bullet's velocity is zero at 1500m, and slows at a linear rate, gravity would act on it for 4 seconds instead of two, and account for the loss of 40 M/S instead of 20. Still pretty small potatoes.
A typical 7.62 NATO projectile will drop sub-sonic at around 800 - 900 M after a time of flight of about 1.8 secs (say about 2700 ft after leaving the barrel) - this is affected very little by angle of firing.
At that velocity and range it is STILL imbued with more than 400 ft/lbs of energy and is a very dangerous item to have land in your lap.
It is quite capable of punching right through a refrigerator.
I would, arbitrarily, say that it would need to drop below 500 ft/sec before I would consider it to be relatively harmless to either human or aircraft skin.
Unfortunately, when fired vertically, it will still be traveling at more than 600 ft/sec at an altitude of 6000 ft.
And the maximum altitude reached is going to be somewhere in the vicinity of 9000 ft before it begins falling to earth.
Which pretty much fits in with ....
When leaving the barrel it would have been rotating at a rate approaching 200,000 RPM.
That is faster than most small vehicular turbochargers and not that far behind a dentists drill.
The ability to maintain stabilised flight is largely dependent on the ballistic characteristics of the projectile and the rifling pitch of the rifle from which it was dispatched.
If in doubt, please refer to standard ballistics calculators from any of the ammunition / projectile manufacturers.
I used Hornady, because they accommodate vertical firing, either up or down
At that velocity and range it is STILL imbued with more than 400 ft/lbs of energy and is a very dangerous item to have land in your lap.
It is quite capable of punching right through a refrigerator.
I would, arbitrarily, say that it would need to drop below 500 ft/sec before I would consider it to be relatively harmless to either human or aircraft skin.
Unfortunately, when fired vertically, it will still be traveling at more than 600 ft/sec at an altitude of 6000 ft.
And the maximum altitude reached is going to be somewhere in the vicinity of 9000 ft before it begins falling to earth.
Which pretty much fits in with ....
.....when I was in basic training in the German army, we learned the safety distance for a G3 (7.52x51) was 3000m
That is faster than most small vehicular turbochargers and not that far behind a dentists drill.
The ability to maintain stabilised flight is largely dependent on the ballistic characteristics of the projectile and the rifling pitch of the rifle from which it was dispatched.
If in doubt, please refer to standard ballistics calculators from any of the ammunition / projectile manufacturers.
I used Hornady, because they accommodate vertical firing, either up or down
Last edited by WingNut60; 28th Jan 2017 at 06:09.
If I remember well, on our military training (many, many years ago) we were warned that AK-47 projectile can be lethal up to 2400m distance – depending on type of bullet and cartridge.
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hen leaving the barrel it would have been rotating at a rate approaching 200,000 RPM.
That is faster than most small vehicular turbochargers and not that far behind a dentists drill.
That is faster than most small vehicular turbochargers and not that far behind a dentists drill.
I'd have to check my notes but to give you an idea, a modern artillery piece that fires out to 17km, only gives it's projectile a slow rotation speed.
AK's are renowned for their inaccuracy, (having been on the receiving end) anything over 500 meters and its hard to hit things accurately. This was mostly likely celebratory fire, or from a scoped weapon?
Not sure how relevant to the original post this is, but I think that you're wrong.
Spin rate is relative to velocity and rifling twist rate (pitch).
Standard calc is Bullet RPM = MV X 720/Twist Rate (in inches)
I was using typical numbers for a NATO round and that gives about 180,000 RPM when fired from a barrel with 10 inch pitch - again, very typical.
Are you sure you didn't mean 3,000 Revs / sec?
The rest of your post seems pretty right. For instance 8 inch pitch and high velocity can cause over-stabilisation; which is actually unstabilisation.
Spin rate is relative to velocity and rifling twist rate (pitch).
Standard calc is Bullet RPM = MV X 720/Twist Rate (in inches)
I was using typical numbers for a NATO round and that gives about 180,000 RPM when fired from a barrel with 10 inch pitch - again, very typical.
Are you sure you didn't mean 3,000 Revs / sec?
The rest of your post seems pretty right. For instance 8 inch pitch and high velocity can cause over-stabilisation; which is actually unstabilisation.
