Recoil


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DF357
November 8, 2003, 04:16 PM
I'm sitting here at work (?) on a Saturday and am really bored. I've covered just about all the posts on this site and several others that I visit regularly. All of a sudden a really dumb but intriging -to me - question came to my mind amidst all this boredom.

Why does the recoil of every gun I know about cause the gun to kick UP ?
Why not down, left, right, etc.

I took my share of physics course in high school and college - along time ago. My first thought is that the axis of the bore might have something to do with it BUT if you aim the weapon in a perfectly level plane with the ground, it still kicks up. Seems it should recoil perfectly backwards.

So call me dumb (I'm really just bored - or maybe I am dumb) but can anyone tell me why a gun always (?) seems to recoil upwards?

Thanks

D(umb)F357

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ChickenHawk
November 8, 2003, 04:27 PM
It's not the gun. It's the way you hold it, and the way your anatomy is designed.

How could the recoil be directed down without your elbows bending the wrong way?

Cheers,
ChickenHawk

Justin
November 8, 2003, 04:48 PM
Quite some time ago there were some free pistol designs that had the barrel mounted underneath the trigger, thereby putting the bore axis directly in line with the shooter's arm. I'd be curious to see how those recoiled.

ceetee
November 8, 2003, 05:00 PM
What they said!

Seriously, you hold almost every gun ever made below the axis of recoil. Your hand (or shoulder) becomes the fulcrum on with the lever (gun) rotates.

There was an obscure revolver made...I'm sure somebody else knows the name, but I've forgotten right now... The firing cylinder is on the botton, not the top, putting the thrust more directly in line with the grip, but the hand and arm is still the hinge point, so it still recoils up and out.

yorick
November 8, 2003, 05:18 PM
It's physics.

The rifle will recoil through (or around) it's center of gravity. The center of gravity is the point at which an object will balance if suspended from a string.

If you are hanging on to it at points BELOW the imaginary line that pases throught the center of mass it will recoil UP, if you were hanging on to it at points ABOVE the center of mass it would recoil DOWN.


Consider a simplidied case:

Muzzel <========|
| <----Center of mass
|=========| butt (and your shoulder)


If you apply a force at the muzzle, and the butt is against your shoulder, it will rotate UP around the center of mass.


If you built a rifle that loked like this:

|=========| Butt (and you shoulder)
| <---- Center of mass
Muzzle <========

it would recoil DOWN.

The vertical component of recoil is directly proportional to the vertical distance between three points, center of mass, the muzzle and the butt (on your shoulder).

That is one of the benifits of the AR-15 style rifle, the center of mass is almost directly in line with the muzzle and your shoulder so you get minimal upward forces exerted due to recoil.

And you all thought physics was boring!


:D :D

CB900F
November 8, 2003, 06:53 PM
Yorick & all;

OK, here we are on a flat frictionless plane in a hard vacuum. Our firearm consists of a breeched barrel, it's round, has rifleing, RH 1 in 10", & is laying on the plane. There is no taper to the breeched barrel. It fires. Normal muzzle velocity is halved of course, the bullet goes forward, the firearm slides back at the same velocity on this frictionless plane ( well, not quite, since there will be some parasitic drag of the bullet in the rifleing but that doesn't really count againt the point we are trying to get to here ). However, we gots da rifleing in da barrel & the friction involved there. The plane is frictionless remember, nobody, including me, said that anything else was frictionless.

So, the barrel torques, but is it going to rise from the plane or remain upon it? It's gonna slide & spin like a dervish, but we don't care. What's it gonna do? Rise or try to go down? Hmmm. This physics stuff means I'm gonna go get another beer.

900F

Kamicosmos
November 9, 2003, 12:07 AM
saw one of those ballistics/forensics shows once. The put a shot gun on a special table that had a little lever to activate the trigger. They were trying to figure out the actual recoil to determine if someone shot himself or not.

They tripped the trigger and that shotgun flew straight backwards off the table and skidded across the floor like twelve feet.

Reason why is for the above reasons....it recoiled along it's various balance points...

P95Carry
November 9, 2003, 12:20 AM
Hardly a need to add .. anything. But think this way ....... if the ''restraint'' ...... your grip on the gun .. the contact with your shoulder, whatever .. is BELOW the bore axis then ... the reaction from the shot being launched MUST, inevitably lead to a rotation about an axis, also below the bore axis. The muzzle lifts ... it cannot go any other way.

Of course, instance 9mm in say, a Hi Power ....... then some torque effect also probably noticeable .... as well as the muzzle lift.

280PLUS
November 9, 2003, 12:24 AM
"Of course, instance 9mm in say, a Hi Power ....... then some torque effect also probably noticeable .... as well as the muzzle lift."

yup, a 9mm hi power will twist as well as rise, thats what placing the weak hand on the bottom of the grip is suposed to do, control the twist

IIRC

m

James Bondrock
November 9, 2003, 02:16 AM
I can't imagine those antique lever-action rifles in heavier calibers, especialy those with crescent-shaped steel buttplates, being very pleasant to shoot. The drop of the stock is excessive, putting the barrel axis very high above your shoulder. (This is actually necessary to put the iron sights in line with your eyes.) This would result in an exaggerated upward flip or torque when fired.

DF357
November 9, 2003, 11:27 AM
However I was watching CONQUEST last night and they were shooting Thompsons and the instructor said that the gun would lift and go to the right when firing. He told the shooters to expect and compensate for that. ?????????????????????????

BTW they were shooting from straight mags not drums so drum internal motion wouldn't count.

Philisphical question:

If a gun were in a vaccuum and frictionless place and there was no one around, when it fired, would it make a noise and would it recoil ?????

:) :) :)

Art Eatman
November 9, 2003, 11:54 AM
DF, in that vacuum, there is no medium in which any soundwave could propagate. Ya gotta have something in which to set up vibrations in the frequencies we know as "sound".

Recoil? Always. That would be unchanged. The powder's burning creates the same amount of gas in a vacuum as elsewhere; the push is gonna be equal in all directions. The constraints imposed by the barrel mean that the force on the bullet equals the force on the bolt's face. F = MA. An absence of friction just lengthens the slide.

A gun twists because of its rifling. The direction will vary with the direction of the spiral. As the barrel imparts spin to the bullet, the torque reaction causes a slight twist to the gun.

:), Art

Mike Irwin
November 9, 2003, 04:49 PM
Starting around World War II, especially in Germany, there were several weapons systems designed, including the FG42 and the MGs 34 and 42, that put the bore axix in direct line with the where the gun would be held on the shoulder. The desire was to reduce the upward rise of the muzzle during firing.

Having fired an MG42, I'd have to say that it certainly helped.

Erik Jensen
November 9, 2003, 10:49 PM
which way does recoil force a handgun in the "gangsta" grip? to the left? or does it still go up? anybody here ever actually try it, just for kicks?:neener:

DF357
November 9, 2003, 11:03 PM
I've been thinking about holding my .45 upside down to see what happens.

Greybeard
November 9, 2003, 11:23 PM
One beer too many? ;) Even sober, please do it with only ONE round in gun. :D

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