Thread: Suppressors - Am I missing something

Originally Posted by Cordite

@gundoc,

With all respect for your conclusion which I can only agree with, you are harsh on other contributors, even arrogant... and in karmic fashion immediately plunge neck-deep into the bog of your version of Munchausen's pigtail self-lift.

To paraphrase your first bit, when a car passenger kicks the dashboard the car pulls forward. We all know this is false. The explanation is that the passenger supports his back against his seat, so the effect of his forward blow against the dashboard is entirely cancelled by his rearward action against his seat as both objects are fixed to the car. It must be understood that the gun and silencer are attached to each other. They are a single unit; the silencer is part of the gun. A blow from a gun against itself (in the form of impingement of its gases against its own baffles) will not pull it forwards.

Astronauts on a spacewalk similarly can not propel themselves through space by slapping their own butts.

Attachment 76413

100% correct. As stated it is a closed system.

You must look at it from an external point of view in order to make sense as I stated earlier. The reduction in recoil from a suppressor can only come from the reduced gas emission speed from the muzzle (which is now the end of the suppressor) and the extra mass added to the system. It is only when something leaves the system (the projectile and gases leave the muzzle) that the conservation of momentum is applied. This will give the initial speed and hence energy of the recoil. @gundoc, this is simple high school physics.

Yes the amount of energy in each direction is the same, but the impact on the shoulder is the speed of the rifle squared x the mass of the rifle. Adding a brake reduces the velocity by directling energy in a different direction. A suppressor slows the speed with which the gas can thrust the rifle back thus spreading the same amount of energy over a longer period of time (Reduces speed of the impact on the shoulder.) As the speed is squared in E=MC2 then reducing speed has a more significant effect on the impact on the shoulder. Total force (work done) remains the same but not as sudden or as violent.

Originally Posted by 300CALMAN

Attachment 76248
That"s one hell of an impact on your shoulder @timattalon

But yes K.E. = 1/2 m v2 indicates that like a bullet, reducing the velocity will make a big difference to force felt.

Yes. Poorly worded on my part. Put it this way, the energy of the projectile (velocity squared x mass) equals the energy of the rifle going in the other direction. Because the mass of the rifle is greater than the projectile then the velocity squared is reduced to get the same total. (Eg a 7lb rifle is approximately 891 times heavier than a 55 gr projectile. ) Your shoulder provides resistance to further increase the mass. This is why pulling the gun INTO the shoulder hurts less than pushing it away. If I assume the shooter is 100kg, then this makes the mass subject to recoil forces 28941 times heavier than the projectile thus reducing the velocity of you going the other way. Holding a rifle away form you means the rifle accelerates into an ompact with your shoulder, but holding it into the shoulder makes your should er part of the same object and you and the rifle accelerate slower due to the increased total mass.

What suppressor (ad the "brake" within the suppressor) seems to do is slow the escaping gasses by capturing them thus reducing noise and delaying the direct transfer of energy by making the explosion take longer. The also slows the transfer of energy so while the energy transferred is the same a further reduction in speed makes the rifle travel slower thus "reducing" recoil. More importantly, by reducing the noise, they body is subconciously less afraid of the recoil and more likely to hold the rifle properly thus reducing FELT recoil rather than the total overall force.

Does that make sense?

Put more briefly, A muzzle brake by itself actively provides a physical forwards push to counteract the recoil. But my understanding of a suppressor is that rather that reduce the amount of energy, is slows the energy transfer to take longer reducing the time that the impact takes place. Same amount of energy transferred (or very similar) but by taking longer the speed / force of the impact is reduced.
To use the car analogy, think of a muzzle brake as an anchor attached to a chain thrown out the back that grabs the ground and applies a pull to the rear that slows the car. Where a suppressor is the act of apply a foot brake that is part of the car. (Not quite the same but I think close enough to get my point.

For all those that are telling us that suppressors cannot reduce recoil forces, please explain why most shooters find suppressed rifles are more pleasant to shoot with what certainly feels like significantly reduced recoil.......

My 7.62x54R boots like a bastard without a suppressor and leaves bruises on my (slightly built) hunting mate after a few shots, (and has flames you can almost spotlight with) but add a suppressor and he can put a couple packets through with no problems or bruising. (And I know this to be true as I have seen it and experienced the difference myself.) If suppressors do not have any effect on recoil, please explain this for us as this is very close to what the OP asked.

Originally Posted by Cordite

@gundoc,



To paraphrase your first bit, when a car passenger kicks the dashboard the car pulls forward. We all know this is false. The explanation is that the passenger supports his back against his seat, so the effect of his forward blow against the dashboard is entirely cancelled by his rearward action against his seat as both objects are fixed to the car. It must be understood that the gun and silencer are attached to each other. They are a single unit; the silencer is part of the gun. A blow from a gun against itself (in the form of impingement of its gases against its own baffles) will not pull it forwards.


Attachment 76413

Two points, 1) there is an effect with the energy transfer in your example- the seat resists the rearwards force at the same rate with that the dashboard resists the forwards force. A better example the person bouncing between the seat and the dashboard hitting them at different times thus producing a rocking motion. Yes the silencer and gun are attached but the gas that hits the brake portion and are forced rearwards are given moments to cool and slow thus the speed with which they hit the rear of the suppressor tube is reduced. If a gas hits the front with a high speed and is forced rearwards within the can then hits the rear of the can with a reduced speed due to the cooling and turbulence encountered, then both ends are not subjected to equal countering forces.

And as a final note, the air thrust forward in your cartoon has been shown to actually work. Poorly but with some gain in forward momentum. Mainly due to the same aerodynamic principle that means an anemometer works. The dome shape at the front resists the air less than the shape behind it.

Originally Posted by timattalon

As the speed is squared in E=MC2 then reducing speed has a more significant effect on the impact on the shoulder. Total force (work done) remains the same but not as sudden or as violent.

You cannot change the speed in that in that equation as c is the constant speed of light and that is the equation that started the whole theory of relativity.

Yes. Poorly worded on my part. Put it this way, the energy of the projectile (velocity squared x mass) equals the energy of the rifle going in the other direction. Because the mass of the rifle is greater than the projectile then the velocity squared is reduced to get the same total. (Eg a 7lb rifle is approximately 891 times heavier than a 55 gr projectile. ) Your shoulder provides resistance to further increase the mass. This is why pulling the gun INTO the shoulder hurts less than pushing it away. If I assume the shooter is 100kg, then this makes the mass subject to recoil forces 28941 times heavier than the projectile thus reducing the velocity of you going the other way. Holding a rifle away form you means the rifle accelerates into an ompact with your shoulder, but holding it into the shoulder makes your should er part of the same object and you and the rifle accelerate slower due to the increased total mass.

You use the conservation of momentum equation m₁v₁ = m₂v₂ to work out the initial velocity of recoil. m₁ is the projectile mass, v₁ is the projectile velocity, m₂ is the rifle mass, v₂ is the rifle velocity.

The energy of the recoil is then calculated from E₂ = 1/2 * m₂ * v₂²

What suppressor (ad the "brake" within the suppressor) seems to do is slow the escaping gasses by capturing them thus reducing noise and delaying the direct transfer of energy by making the explosion take longer. The also slows the transfer of energy so while the energy transferred is the same a further reduction in speed makes the rifle travel slower thus "reducing" recoil. More importantly, by reducing the noise, they body is subconciously less afraid of the recoil and more likely to hold the rifle properly thus reducing FELT recoil rather than the total overall force.

Does that make sense?

@timattalon E=mc2 is Energy = mass x (speed of light)squared and is not relevant to this discussion.

The post above by gadgetman has the relevant equations.

Originally Posted by Cordite

@gundoc,

With all respect for your conclusion which I can only agree with, you are harsh on other contributors, even arrogant... and in karmic fashion immediately plunge neck-deep into the bog of your version of Munchausen's pigtail self-lift.

To paraphrase your first bit, when a car passenger kicks the dashboard the car pulls forward. We all know this is false. The explanation is that the passenger supports his back against his seat, so the effect of his forward blow against the dashboard is entirely cancelled by his rearward action against his seat as both objects are fixed to the car. It must be understood that the gun and silencer are attached to each other. They are a single unit; the silencer is part of the gun. A blow from a gun against itself (in the form of impingement of its gases against its own baffles) will not pull it forwards.

Astronauts on a spacewalk similarly can not propel themselves through space by slapping their own butts.

Attachment 76413

I am well aware that you cannot stand in a bucket and pick it up by the handle, however my comments are backed up by years of experimentation and manufacture (probably more than any current manufacturer). Suppressors are not a 'closed system' and, despite the efficiency of any baffle system, a decent percentage of the gases exit the muzzle in front of, and behind, the bullet. I guess I will just have to set up an experimental pendulum (friction free as opposed to a slide) and publish the results of the recoil dampening effect of various suppressors and muzzle brakes.

I don't intend to be harsh on individual opinions but I have heard too much garbage and pseudo-scientific rambling on the subject of suppressors over the years, and it irritates me!

Energy is energy, work is energy expended over time, force felt (work) is affected by the total energy expended and the time/pattern it is released over..... suppressors alter the pattern of energy expended over time which changes the perception of felt force. They do not alter the total amount of energy released.. and they have no effect on converting energy in felt recoil into a different direction.

The best example I can think of would be a compressor storage tank. Dumping the contents over a short time increases the felt force.... the same amount of energy is released with a smaller valve over a longer time...

Muzzle brakes on the other hand convert some of the total energy released into forwards force by redirecting some of that energy in the opposite direction.... different process....

Originally Posted by Sidney

Energy is energy, work is energy expended over time, force felt (work) is affected by the total energy expended and the time/pattern it is released over..... suppressors alter the pattern of energy expended over time which changes the perception of felt force. They do not alter the total amount of energy released.. and they have no effect on converting energy in felt recoil into a different direction.

The best example I can think of would be a compressor storage tank. Dumping the contents over a short time increases the felt force.... the same amount of energy is released with a smaller valve over a longer time...

Muzzle brakes on the other hand convert some of the total energy released into forwards force by redirecting some of that energy in the opposite direction.... different process....

Though, because the gases cool in the suppressor, some of the kinetic energy is turned into heat energy and dissipated. This is why an attached suppressor is not an entirely closed system.

Originally Posted by gadgetman

Though, because the gases cool in the suppressor, some of the kinetic energy is turned into heat energy and dissipated. This is why an attached suppressor is not an entirely closed system.

That would alter with the latent heat inside the suppressor which is quite a bit especially after a few shots with a suppressor cover on.

Also on how fast the heat is transferred, a titanium one I fired a shot through on a 338 LM nearly burnt my hand after only one shot

Work is energy transferred. Force x distance. Power is energy transferred over time.

You are quite correct Stug.. apologies... Power is the correct variable..

I wonder how much the conversion of kinetic energy into heat would actually reduce percieved recoil? Cooling the gases would reduce volume as well?

If you run the numbers on a recoil calculator with the mass of the rifle and projectile and velocity of projectile, but only 1gr of powder, you get a very low recoil, about 1/3 compared with full amount of powder.





The extra mass of the suppressor only removes about 2-3ft/lbs of recoil energy.

Originally Posted by Sidney

I wonder how much the conversion of kinetic energy into heat would actually reduce percieved recoil? Cooling the gases would reduce volume as well?

No, the volume is constant (the container) but the pressure would reduce. PV = nRT. That is why the gases limp out of the suppressor. I would say the pressure would drop a lot. Compare the mass of the gases (roughly the charge) to that of the suppressor.