The Science of Aerial Gunnery

Started by gcode, January 08, 2021, 05:51 AM

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gcode

January 08, 2021, 05:51 AM Last Edit: December 31, 1969, 04:00 PM by Guest
I never knew this..

https://gunsmagazine.com/our-experts/guns-and-rotors/">https://gunsmagazine.com/our-experts/guns-and-rotors/


QuoteThe practical physics governing aerial gunnery out of a moving aircraft is absolutely fascinating. Our M60 machineguns sported barrels rifled with a 1:12" clockwise twist. If my math is correct it means each M80 147-grain FMJ bullet travelling around 2,800 feet per second is spinning at 168,000 rpm. Any object freely subject to gravity accelerates toward the center of the earth at 32.17 feet per second squared. This is why when we shoot our weapons the bullets invariably arc downward until they eventually strike the earth. Factor in a 160-knot (184 mph) crosswind, however, and some of the most amazing things occur.

When firing bullets with a clockwise spin out the right side of a moving aircraft, the airflow across the spinning projectile creates a low-pressure area on the top of the bullet. Driven by the Magnus Effect, this causes each bullet to behave like its own miniature aircraft and fly upward. The practical result is a gunner trying to hit a target on the right side of a moving aircraft actually has to aim underneath it and let the bullets fly upward to impact where desired.

The same effect is manifest in the opposite direction on the left side of the aircraft. The low-pressure area is on the bottom of the bullet and causes the round to plunge precipitously toward the ground sooner than might be the case if fired from a stationary platform. The faster the aircraft the more pronounced the effect. In practice this makes a huge difference.

RobertELee

#1
January 08, 2021, 06:20 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Wonder why they wouldn't do opposite barrel riffling for each side of the aircraft?

YoDoug

#2
January 08, 2021, 07:50 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Quote from: RobertELee post_id=2473 time=1610115602 user_id=55Wonder why they wouldn't do opposite barrel riffling for each side of the aircraft?


It must be opposite riffling to make it behave differently on each side. I can't think of any other reason why a projectile fired from either side of a symmetrical plane would behave differently.

YoDoug

#3
January 08, 2021, 07:53 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Take that back, I just noticed it is referring to helicopter mounted weapons. That makes sense.

RobertELee

#4
January 08, 2021, 08:33 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Quote from: YoDoug post_id=2483 time=1610121233 user_id=58Take that back, I just noticed it is referring to helicopter mounted weapons. That makes sense.


I would think it would be any moving aircraft. (However, are there still airplanes with side mounted gunners?) The faster it is traveling the more pronounced the effect to be.

But all I was saying in my first post was if they had mounted guns with the proper/opposite rifling for each side of the aircraft it would allow the bullets to act the same.

Maybe I'm just overthinking it and there really is no aiming as a sidegunner, just pull the trigger and move the bullet trail where needed.

Sounds like a really cool effect that I would love to experience in person.

Matthew Hajicek

#5
January 08, 2021, 08:52 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Quote from: RobertELee post_id=2489 time=1610123581 user_id=55(However, are there still airplanes with side mounted gunners?)


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gcode

#6
January 08, 2021, 09:41 AM Last Edit: December 31, 1969, 04:00 PM by Guest
Quote from: RobertELee post_id=2489 time=1610123581 user_id=55
Quote from: YoDoug post_id=2483 time=1610121233 user_id=58Take that back, I just noticed it is referring to helicopter mounted weapons. That makes sense.


Maybe I'm just overthinking it and there really is no aiming as a sidegunner, just pull the trigger and move the bullet trail where needed.

Sounds like a really cool effect that I would love to experience in person.


The article said that modern side mount guns have sights that comp left/right mounting and aircraft speed
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