Author Topic: Question about Gun leathality  (Read 282 times)

Offline cajun

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Question about Gun leathality
« on: May 06, 2002, 01:07:26 PM »
I noticed that it seems to take like 100-200 7.7mm mg rounds in a plane to bring it down where a 12.7mm mg takes only about 10-20 rounds shouldnt 2x7.7 mm mg rounds be more powerfull than 1x12.7mm round? And it is the same with 20mm cannons, 2-3 hits will take most things down.

Offline Ghosth

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Question about Gun leathality
« Reply #1 on: May 06, 2002, 04:53:15 PM »
Just the way it should be actually.

Due to bullet weight and rate of fire two .50's actually put more bullet weight onto target than then 4 .303's.

7.7 mm roughly equivelent to the 303 british round btw while perhaps not quite as fast.
Same holds true for the 12 mm

If your shooting at a 4" wing strut at 100 yards would you use

A BB gun that would barely reach 100 yards? (0.177)
B .22 cal rifle that would reach it and hit it accurately, but not penetrate it. (0.22/ 5.5mm)
C .30 cal rifle bullet that will hit it and if you hit it enough times in the same spot MAY cause it to fail. (7.7 mm)
D .50 cal MG bullet that  can hit it and with
a few hits in the same area will cause it to fail every time.  (12 mm)
E a 20mm Explosive round that if it hits it will cause it to fail almost every time.

Many a pony pilot would disagree that it only takes 10 to 20 rounds to damage something vital.

Cannon yes, there 5 hits or so in "one" spot should kill what it hits.

The larger the diameter the more shock damage it delivers, the higher the chance for catastrophic failure = dead plane.

Thats why so many people in AH prefer cannons.
Heck thats why the F4U-1c was perked. 4x20mm hispano's with large ammo supply.
« Last Edit: May 06, 2002, 04:55:16 PM by Ghosth »

Offline humble

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Question about Gun leathality
« Reply #2 on: May 08, 2002, 05:35:59 PM »
I'm not a engineer but the weight of the bullet effects the amount of energy transfered. The hitting power of the round increases significantly as the weight increases (assuming equal velocity)

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Offline Pei

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Question about Gun leathality
« Reply #3 on: May 09, 2002, 08:10:02 PM »
Well basically (physics student mode on):
damage = energy transfered from the round to the target (more or less)

Now assuming if a hit occurs then the same proportion of the projectile's energy wiill be transfered for every type of bullet (which isn't of course the case in real life).

Damage  = Energy transfered = some fraction of total energy

and

Total energy = (Kinetic Energy + Explosive Energy)
 
(ignoring secondary effects like fire from incendiary rounds)

Only cannon shells have explosive energy (obviously)

so for machine guns
Damage is proportional to kinetic energy

and Newton will tell you

Kinetic energy = 1/2 * mass of bullet * velocity of impact squared

The first point to note is that aparently speed (or in fact velocity) has a much higher effect on damage than mass. .50 cal rounds have a much higher muzzle velocity than 7.7mm rounds and also
.50 cal rounds are much larger (greater volume) for a similar density (assume both bullets are mostly lead) and so have greater mass as well.  Therefore .50 cal rounds are likely do do a lot more damage.

Once you get to cannon you have to add in the explosive energy (though they tend to have lower muzzle velocities) and you also have to consider that they are  much less likely to overpenetrate (i.e. travel right through the airframe) and so are likely to transfer more of their energy and thus do more damage.

There will be a test later :)