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/sci/ - Science & Math

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Can someone here please explain the physics of the AK-107s counter balance "recoil reduction" system? Seems to me that a weight moving forward would actually increase recoil, but I've read it somehow smoothes out the recoil impulse and reduces muzzle rise.
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>>>/k/
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>>10716573
It's a physics question, that's probably where he came from
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>>10716559
First off Recoil and 'muzzle rise' or perhaps better named 'muzzle flip' isn't the same thing.
When you fire a cartridge it generates a certain amount of energy, it drives the bullet and gases out the barrel and the rest goes into the gun.

If you can keep parts of the mass of the gun moving for a longer duration of time you can smooth out the felt recoil by delivering less force per unit time into the shooter.
if you can make part of the mass of the firearm move in a direction other than backwards towards the shooter you essentially cancel out portion of the 'felt' recoil by keeping the forces inside of the gun.
You can also control how the muzzle behaves by directing the ejected gases so it presses the barrel in such a way it counteracts the direction the center of mass of the firearm wants to pivot.
FN P90, Barret M82 or Kriss Vector are weapon systems that famously uses recoil reduction systems you can prob find lots of information on rather than the AK-107 that's more exotic among the guntubers.

I'd recommend the channel 'forgotten weapons' if you're interested in learning about the mechanics of guns.
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The weight or "shuttle" exchanges momentum with gas in a pressurized chamber, in the opposite direction to that of the exchange between the bullet and the gas formed by the ignition of the gunpowder charge. Because the shuttle is moving in the same direction as the bullet, it is natural that your intuition would tell you that it increases the kick, rather than decreasing it. However, it is the exchange of momentum between the pressurized gas and the weight that is opposite. The muzzle rise is reduced because the barrel is more massive at the end where the shuttle is exchanging momentum with pressurized gas. It effectively has greater inertia, and therefore resists being accelerated in any direction.
Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.
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>>10716559
Looks to me like what they're trying to do is cancel out the effects of the BCG going backwards. In a normal gun the BCG takes up a bunch of the recoil momentum initially and then delivers it all fairly abruptly when it reaches end of travel. This can cause things like "kick" and muzzle climb since the moving mass is off-axis to the shoulder. By using a counterweight you can cancel this out and be left with just the original recoil impulse that's smoothed out by the significant mass difference between the gun and the bullet as well as being right on the bore-stock axis.
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>>10716559
The jerk generated by the bolt is dampened by the forward sliding piston, as it absorbs some of the force. So the energy from the bullet exploding is soaked by both the bolt and the forward sliding piston. Also, the Piston is moving in the opposite direction which reduces the retrograde acceleration of the rifle as it fires. Sort of like shocks on a car
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>>10716614
>if you can make part of the mass of the firearm move in a direction other than backwards towards the shooter you essentially cancel out portion of the 'felt' recoil by keeping the forces inside of the gun.
Then why do blow forward guns have more recoil than blowbacks?
>>10716655
>However, it is the exchange of momentum between the pressurized gas and the weight that is opposite. The muzzle rise is reduced because the barrel is more massive at the end where the shuttle is exchanging momentum with pressurized gas. It effectively has greater inertia, and therefore resists being accelerated in any direction.
>>10716729
>and be left with just the original recoil impulse that's smoothed out by the significant mass difference between the gun and the bullet
>>10716768
>Also, the Piston is moving in the opposite direction which reduces the retrograde acceleration of the rifle as it fires.
Could I get these in layman's terms? Sounds pretty simple but I never took physics in school.
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>>10716573
>Go ask a bunch of right wing nut jobs and nignogs how the gun actually works
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>>10717043
was hoping that was gif/webm
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>>10716573
I think he wants a scientific answer and not a schizo essay about jews and liberals
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>>10716559
I can't find any graphs of semiauto rifle recoil force but based on the mechanism I would wager this dampens the impulse when the bolt hits the end of travel.
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>>10717589
this, it dampens felt recoil
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>>10716559
the bolt carrier on AK's is so heavy that it increases the felt recoil
you know how there are some competition AR's with ultra light bolt carriers? that's basically the same thing here' just that they can't make the bolt lighter because of reliability.
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Without external force, the CoM of two object would stay constant.
As the white typical bolt carrier moves back and front, in order to keep the whole gun's center of mass still, the rest of the gun would move front and back, rocking the gun.
Now having the yellow counter weight moving front and back, so that the frame don't need to move. If perfectly balanced, it should just be 2 masses moving into and away from each other, no CoM change for the whole gun.
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>>10717043
Objects that are moving have more mass than identical objects that are stationary. The kinetic energy transferred between the shuttle and the pressurized gas at the business end of the barrel increases the mass and inertia of that region in the following way. The transference of momentum between the shuttle and the gas occurs rapidly at a point that is local to the end of the barrel, the gas is pushed in all directions against the inside of the shaft, again localized in a small area near the business end of the barrel. You can imagine that the shuttle is carrying the kinetic energy first, then it is transferred to gas through force of collision. Now the gas is carrying kinetic energy, which it transfers to the walls of the hydraulic shaft. The force exerted by the collision of the gas with the walls of the shaft accelerates or pushes the shaft up, down, left, right, forward and backward. The thrust experienced by the weapon, again, is localized near the business end of the weapon. You can think of mass and inertia as the net thrust or acceleration of an object towards its center of mass.
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>>10718569
yeah and bolt actions have no recoil at all am i right?
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>>10716559
>bull propels forward
>recoil pushes gunbackward
>weight moves forward

Fbullet - Frecoil + Fweight = 0
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>>10718569
but the bullet and propellant is already accelerating down the barrel, shifting the CoM anyway
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>>10718854
uhh what?
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>>10718854
>assuming satic condition of ΣF=0 when the system isnt static
yikes
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>>10717043

Blow forward guns have more recoil because instead of just having the equal and opposite force of the bullet moving out of the gun, you also have the force of the mass of the bolt going forward.

Presumably, the AK-107 is engineered so that so you get something moving forwards while the bolt is going backwards, and something going backwards while the bolt is going forwards.
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>>10719094
do you think that bolt actions have no recoil either?
they've also got equal number of parts moving forwards and backwards
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>>10719106

In a bolt action such as the Mosin Nagant, you don't have any parts moving backwards.

In a semiautomatic rifle like the M1 Garand, the bolt just moves backwards until it collides with the rifle at the end of its travel.

There isn't anything that uses expanding gasses to push it forward.
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>>10719274
>There isn't anything that uses expanding gasses to push it forward.
neither is there in the 107, what benefit would that have?
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>>10716559
Felt recoil in semiautomatic rifles is mostly from the bolt carrier impacting the back of the receiver. In other words after firing, the shooter only experiences recoil until the bolt has fully opened and hit the back of the receiver. Some guns try to mitigate felt recoil by using constant recoil systems where the bolt carrier and recoil spring(s) are finely tuned such that the bolt never touches the back of the receiver. The AK-107 uses a mass traveling the opposite direction to cancel out the momentum of the bolt carrier, thus mitigating some felt recoil
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>>10718879
Indeed, besides the accelerating bullet, the mechanism itself don't introduce more oscillation post shooting.
The only way to make sure there is no CoM change for the whole system is to employ recoilless system that shoot counter-weight or gas backward to counter.
The peak acceleration of that bullet happens before the gas is directed to the gas system, so you can't count on it to counter the reactive impulse bullet introduces.
Many cannons have recoil damper than allow the barrel to move backward to ease the recoil from launching the bullet, but fixed barrel is more suitable for small arms.
Assault rifle that undergas with rifle length gas system or use constant recoil system is much easier to handle recoil might suggest that the fact the oscillating bolt has more to do with the felt recoil than the bullet itself.
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>>10720031
recoilless tend to pull forward, don't they?
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>>10720032
Never fired one myself.
if the impulse from the gas is more than the impulse of the projectile, then yes.
I had only seen the video that someone fired law or AT4(I can't remember) without holding it firm and the casing just slide forward out of his hand.
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>>10717406
You're an intellectual dumbass.

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