Do suppressors function as a brake?

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Buck13
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Do suppressors function as a brake?

#1 Post by Buck13 » Mon Oct 29, 2018 2:40 pm

It seems that since the suppressor slows the jet of gas from the muzzle, it should greatly reduce the effect of that jet on recoil (which supposedly is modest but noticeable).

I don't seem to see a lot of talk about this, maybe because I don't read about suppressors much. Since the can adds weight and length which would presumably also reduce muzzle flip, do people just not realize there are other things happening?

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Re: Do suppressors function as a brake?

#2 Post by SubRosa » Mon Oct 29, 2018 3:13 pm

I have 3, .22, .30, .45.

Never noticed any reduction.

In the case of the .30cal, it goes on an HK91 and requires a different locking piece to slow down the action so as not to hammer you.

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Re: Do suppressors function as a brake?

#3 Post by AndyH » Mon Oct 29, 2018 3:59 pm

I use my 7.62 mm DIY can on my AR-10 and AR-15 (5.56). Mine feels like a regular barrel that's a couple of inches longer. I'm guessing that Newton's laws remain in force even if the gases are slowed by the muffler.
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Re: Do suppressors function as a brake?

#4 Post by max129 » Mon Oct 29, 2018 4:43 pm

AndyH said:

Newton's laws remain in force
And so they do. A suppressor should only lessen recoil if it changes the laminar flow vector of the gas (direction of the blast). Some people think porting works because it "releases gas" - but the effect would simply be that of a shorter barrel if the 'release' was all that was involved. Porting and 'brakes' work because they change the direction of some of the blast. So a suppressor could lower recoil if it redirected the blasts laterally. But that could actually increase the sound (as porting and brakes do). The increased noise is caused by the turbulence effect (Hagen-Poiseuille’s Law) the small size of the ports increase the turbulence and thus the sound.

One reason gas operated weapons have less perceived recoil is that some of the directional pressure goes backwards to operate the action. A suppressor is a sound baffle - as such, it must create a "random" buffer for the sound pressure - that randomness requires avoiding a specific directional vector.
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Re: Do suppressors function as a brake?

#5 Post by Bisbee » Mon Oct 29, 2018 5:17 pm

Not knowing the science behind it like what Max described, if you look at how some muzzle brakes redirect muzzle flash up and rearward to the sides, it is effectively creating a downward and/or forward force to help counteract muzzle rise and recoil. A can without such ports to redirect the muzzle flash would not creat such forces to help as a muzzle brake, IMHO.
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Re: Do suppressors function as a brake?

#6 Post by Marlene » Mon Oct 29, 2018 6:29 pm

The precision competition guys seem to think so.
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Re: Do suppressors function as a brake?

#7 Post by SubRosa » Mon Oct 29, 2018 6:33 pm

They do lengthen combustion pressure to some extent, especially in recoil or gas operated guns.

One perceives less recoil & jump due to the increased weight, as there is quite a bit of metal in one.

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Re: Do suppressors function as a brake?

#8 Post by max129 » Mon Oct 29, 2018 9:55 pm

SubRosa said:

recoil & jump due to the increased weight


This I believe 100% - if you put a heavy can on the end, you could increase mass enough to dampen F=M*A. And if it is long enough, it could change the torque.

But is it not the 'suppression' causing the effect, simply mass and leverage.
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Re: Do suppressors function as a brake?

#9 Post by SubRosa » Mon Oct 29, 2018 10:05 pm

Indeed, from personal experience.

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Re: Do suppressors function as a brake?

#10 Post by FlyGuy » Tue Oct 30, 2018 7:25 am

I have a SilencerCo Harvester on the end of a Savage Arms 30-06. I shoot from a bi-pod on a bench exclusively. My perception is that it definitely make a difference. I often get asked by my guests or people next to me to compare shooting with and without the can. Even they are surprised by the change of felt recoil. The best way I can describe it to people is that the gun "Bounces" more then kicks.

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Re: Do suppressors function as a brake?

#11 Post by max129 » Tue Oct 30, 2018 9:21 am

Well, one thing I am not is an expert on the internals of suppressors. If any are designed to divert the directional vector laterally, then you could get more of this effect. The few suppressors I have seen cut open (on the inter-webs) do not seem to be built in that fashion, but that does preclude some built to divert gases orthogonal to the direction of fire. There ARE spring/weight dampers - my ignorance may be showing here: I understood most "suppressors" were simply sound abatement devices. (See the end notes for more on these).

If you are bored by ballistics and simple equations, skip the rest of this post.

Early in the process of learning Physics, we are trained to listen for references to 'fictitious' or 'pseudo' forces - things that are not there. For example, when you swing a weight on a string if 'feels' like the weight is pulling back on the string. No such thing. The weight is simply trying to go in a straight line. (Albeit, while forced to travel in a curve.)

Similarly, one does not need to do any equations to line draw the directional forces in a rifle. The explosion can only exit in one direction, thus the force is in the opposite direction. Enter porting and this changes. Some of the gases are ejected laterally and that DOES change the force going backwards.
FlyGuy said:

The best way I can describe it to people is that the gun "Bounces" more then kicks.
And as can clearly be seen in the picture of the Silencer Co Harvester, this has lateral ports - none of the suppressors I see in LGS have these ports. I am ignorant regarding the popularity of ported suppressors and sound abatement only suppressors.
https://silencerco.com/silencers/harvester/

As I said, I can claim no expertise WRT suppressors, but again Physics comes into play. It seems that the primary design of most suppressor has nothing to do with escaping gases and everything to do with dampening the sound percussion (the effect of air being rapidly compressed by the explosion both within the chamber and as the projectile and hot gases exiting the barrel.) These compressions on the air around the exit cause a series of vibrations in a frequency we experience as sound. The intent of a suppressor is to dampen these oscillations and thus reduce the sound. But the sound being created by the explosion should be mostly omnidirectional - and thus the dampening should be omnidirectional.

The force from the sound itself is negligible - The process by which sound propagates in the air dampens the force as the inverse square of the distance. I have never seen anyone measure the sound of riles, but this chart looks basically correct:
https://www.thehighroad.org/index.php?t ... ns.646806/

According to these data, a .30-06 rifle normally creates 160 dB - and that seems about right. If you tried to capture the effect of that sound as air pressure pointed back towards the shooter, it would not move a toddler backwards. (Say by placing a light piece of plywood and measuring the instantaneous pressure caused by the sound itself.)

One reason good suppressors do not seem to cause directional errors in the bullet flight is that the sound is so much slower than the bullet. (Older suppressors relied upon gaskets, which touched the bullet - bad idea and they DID slow things down, as well as cause serious accuracy errors - new suppressors do not touch the bullet.)

The nominal speed of sound in dry air and sea level is 767 mph (I am doing this in miles and feet since most of our forum members seem to be Americans ;-)

(767 miles/hour * 5280 ft/mile) / 3600 seconds/hour = 1,125 feet/second = speed of sound.

A .30-06 bullet exits the barrel at between 2,700 f/s and 3,300 f/s. Even at 1000 yards, the bullet is traveling 75 f/s faster than sound.

Thus, inside a suppressor, the "sound" is being dampened after the bullet is gone, because the sound propagates at 1125 f/s and the bullet moves more than twice that fast on exit.

Again, YYMV, some clever designer may have found a suppressor enhancement that uses lateral gas direction as an agent to baffle the sound. In this case, I would expect some noticeable sideways gases discharging from the suppressor - I lack the experience to comment on this. All the suppressors I have handled in a gun store seemed heavy to me. I looked up a couple online and the weight seems to vary from 10oz (283 grams) and 14 oz (396 grams). In addition a 7 inch (18 cm) suppressor adds 1/3 the length of a 22 inch (56 cm) rifle barrel and we begin to see Archimedes' leverage ("Give me a lever long enough, and a place to rest it, and I will move the earth.")

Suppressors add mass and leverage at a critical point in the barrel geometry. Frankly, it would take a lot of work in a good lab to isolate all these forces, and I have not found any research of it having been done. People seem to buy a "net effect" in a suppressor, and the benefits, while possible to measure in isolation, seem to combine in subjective ways.

One thing I have found for certain in years of examining ballistics tables: bullets are pure Newtonian Physics. You can derive the air resistance directly from the velocity loss over time (gravity does not slow a bullet down, it just makes it fall). And you can exactly match the rate of fall with the gravity equation, modulated by the changing rate of bullet flight. The only ammunition that does not follow these rules is closely spaced shotgun pellets, which seem to create some interference amongst each other as they travel.

CAVEAT: There are people who have decades more experience with actual suppressors than I do. Some may have been engineered for exactly the effects noted above - but I cannot find them.

Here is an example of a 'recoil suppressor' that is based on increasing mass and length as well as adding a spring shock absorber:
http://www.mercuryrecoil.com/suppressors/index.htm Basically, these work because the fontal weight (mass - a chunk of metal) resists changing direction. This compresses the spring, which conforms to Hook's Law (f(x) = -Kx^2) - and the compression takes time, then it uncompresses and the mass returns to its origin point. This could account for the BOUNCE effect reported above - see if your suppressor has a spring in it (I don't think the Harvester has a spring.)

Important, these do not LOWER the recoil, they slow it down, which has the same subjective effect. You will still experience the same total recoil, just spread over more time.
(Side gas ports/brakes can actually reduce rearward recoil - springs cannot, but slowing down recoil feels like reduction.)

But any suppressor that is focused 100% on sound abatement should have the recoil reduction limited soley to the length+mass increase.

If you have a suppressor that combines both sound abatement and perceived recoil, my guess is that it has both springs and weights inside - or the porting devices. In order for the spring/weight combination to do any good, there is a technical term we would use for the mass: "a heavy sucker". A spring and a light damper weight would not change perceived recoil. So if you have an effective spring/weight recoil damper, I would venture it is heavy. If it is ports, they would have to be big to work on a rifle, and you can see the large ports on the Harvester.
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Re: Do suppressors function as a brake?

#12 Post by AndyH » Wed Oct 31, 2018 12:25 pm

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Re: Do suppressors function as a brake?

#13 Post by max129 » Wed Oct 31, 2018 2:01 pm

Great video - Loved it.

All these are 'baffle' designs. They contain all the force within the device. There is no lateralizing of the forces and no "spring" effect. So these should primarily make the rifle quieter. But if you draw a picture of where the forces go, there is nothing that would reduce the backward thrust, and I don't see how it would 'slow down' recoil.

So what we seem to have here is a semantics issue: "suppress" means to reduce or stop an action. It looks like I have now seen 3 kinds of devices (some combine of course):

1) Sound suppressors (silencers) - they baffle and dampen sound. If they are long and heavy, they should also reduce perceived recoil, but only with length x mass effect.

2) Ports/Brakes which lateralize gases and reshape the backward forces to sideways and backwards

3) Spring recoil reducers, which use internal mass to compress a spring (or move it through heavy fluid) - these do not 'reduce' recoil, but they slow it down enough that the perceived recoil is less.

Combinations: Silencer + gas ports (Harvester, Silencer Co)

Frankly, I have not seen most of these at either a gun range or in any gun store - perhaps it is all online? All I see in my LGS is "silencers" and "brakes" which are rather single purpose.

So some of the answer to the original question is "What did you buy?" If it has ports on the side, it could truly reduce reward force. If it has springs, it will slow down recoil enough to feel like it is reduced in toto. If it is heavy and long, you get the mass/leverage effect.

In effect, 100% of the 'force' of the explosion is directed out the barrel and therefore 100% of the recoil is in the rearward direction. You cannot change that (unless you divert it sideways - ports/brakes, or backwards with gas autoloaders). Some small amount of the energy of the explosion is emitted as heat and light. I think it would be hard to measure this effect. Brakes and ports do move some of the force to the side, which really reduces the rearward force. But anything that captures the pressure (for any reason) and does not redirect the direction, simply results in the same net rearward force.
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Re: Do suppressors function as a brake?

#14 Post by AndyH » Thu Nov 01, 2018 2:10 am

I'm not super expert on cans by any means, but did some homework before deciding on my DIY project. The only devices I've seen with springs are for pistols - the spring and pistol add some extra push on the slide to cycle the action - it uses gas to make up for the extra weight of the can on the barrel. I've not seen rifle cans with springs. I think the OP was about sound suppressors (AKA 'silencers').

My AR-10 project, though, definitely has a softer felt recoil when suppressed. As a sound suppressor uses baffles and volume to slow the release of gasses, I expect the 'softer' feeling is a result of the longer period of time it takes for gases to vent as you noted.
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Re: Do suppressors function as a brake?

#15 Post by max129 » Thu Nov 01, 2018 9:12 am

Andy said:

I expect the 'softer' feeling is a result of the longer period of time it takes for gases to vent as you noted.
So your saying that the gas entrapment and the baffles are acting like a 'spring' - the gases compress locally then exit at a slower enough rate to slow down the impact moment. That would account for a "bounce' effect.

I've got a buddy who is a laminar flow engineer. I'll ask him for some pointers to where I can look for how they model this kind of thing.

But your explanation makes perfect sense. Anything that increases the time over which there impact moment is delivered could seriously reduce the perceived impact.

And my personal experience is less than yours. I have fired a few sound suppressor firearms, but they were .22lr and the overall effect was not overwhelming.
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Re: Do suppressors function as a brake?

#16 Post by YankeeTarheel » Thu Nov 01, 2018 9:49 am

I haven't been following this thread but looking at the video, something seemed blatantly obvious to me:
An application of Newton's 3rd(?) Law: For every action there is an equal and opposite reaction.

I watched the gasses exit the muzzle race forward, then hit the wall of the front of the see-through suppressor.

Obviously gasses exiting the muzzle will push the rifle back, but when they hit the front of the suppressor wall, they must then pull the rifle forward again--Newton!
As this all happens in micro-seconds, the overall result MUST be less recoil, as the gasses slamming the front of the suppressor counter the forces it driving it backwards.

It was simpler and more powerful than what I had thought--that, say, an S shaped chamber to capture, redirect and dissipate the gasses causing the recoil (thinking about car and motorcycle mufflers and how they are tuned--2-stroke bikes especially depended on "tuning/timing" to set up a precise exhaust back-pressure that holds the incoming fresh gas/air charge from rushing out of the cylinder prematurely just long enough).
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Re: Do suppressors function as a brake?

#17 Post by max129 » Thu Nov 01, 2018 11:54 am

YankeeTarheel - clearly there are a lot of complex interactions going on, but the forces must "net out" - The only things that can reduce reward total recoil are:
- side ejection ports which change the directional vector flow
- conversion of some of the energy to forms that do not cause back pressure (heat, light) - sound, BTW, is a byproduct and not an energy leak like heat and light are.

All other effects seem to be caused by increased mass or a change in the timing of the energy that is delivered rearward.

BUT, it looks like one of the effects, larger than I would have guessed, is that by being trapped and moving forward/backward as you described, the gases "bounce" and this will do the exact same thing as a spring: lengthen the total energy recoil cycle. My friend who is a laminar flow expert said he is not the right person. He forwarded my questions to a propulsion engineer at JPL who deals with all these multiple effect issues. There is an impact equation they use which deals with the distribution of the forces over time, and slight variations in timing reduce the perceived force effect in some non-linear ways.

One of the issues with gases is they refuse to act like solids or liquids :-) So the "bouncing" is not exactly like a spring in that it is not simple harmonic motion (normal dampening). At some point in the "bouncing" back and forth, the gases bumping into one another at the molecular level dominates over the collection explosive path - randomness creates its own final dampening. That is why automobile shock absorbers are hooked to serious springs. The springs do all the real work, but they will bounce long after you want them to. The mass filled shock absorbers refuse to keep bouncing and dampen the oscillations much more quickly.

So apparently, just changing the timing of the rearward recoil a tiny bit (making the force get delivered over a few more milliseconds) changes the perception of the impact greatly.
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Re: Do suppressors function as a brake?

#18 Post by YankeeTarheel » Thu Nov 01, 2018 12:07 pm

Max, I certainly don't claim to know flow dynamics of gasses and forces work at the subtle, granular level, but I could clearly see those forward shooting gasses hit the front wall of the suppressor and MUST pull the rifle forward.

Of course, a brake re-directing the gasses sideways should mitigate a large part of the recoil--airliners create breaking forces by directing the exiting engine gasses forward.

A very large can, can, by sheer volume, allow energy to dissipate across more space, mitigating some recoil.

I'm interested in what your friend's friend has to say.

It's all academic for me because here, in NJ, brakes are allowed, but only if they are permanently attached. Suppressors and flash suppressors are simply illegal under our laws. I get why suppressors are illegal, although mitigating 115 to 120 decibels down to 85-90 decibels isn't silencing means I don't agree with the law--it's based on bad fact. But the flash suppressor ban makes even less sense than the reduction in June from 15 rounds to 10 rounds for semi-auto removable mags. I have NO idea why they ban that.
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Re: Do suppressors function as a brake?

#19 Post by max129 » Thu Nov 01, 2018 1:07 pm

YankeeTarheel - I do not disagree - and if enough of the gas is allowed to finally dissipate via side ports (any holes) then we are in agreement. In physics, there is the concept of a contained environment. One cannot create a box, stand in the box, throw a mass against the wall and move the box in a meaningful way. The reason is that all of the forces net out. The total motion of getting ready to throw the mass against the wall of the box, and then releasing the mass create a total of zero forward energy inside the box.

Any kid will tell you this is *BS* because you CAN sit in a box and move your weight in such a way that the box "scoots" across the floor. So the kid will tell you physics is wrong.

It's not. In order to get a box to skid across the floor, the kid is using a series of -quick- forward motions coupled with slower wind ups. So the quick forward motions break the friction of the box on the floor to move it forward, but the wind up and the recovery of the scoot are below the friction threshold (because they are slower) and the box does not move backwards. If the floor were frictionless, the kid would never move at all. (And Physics is often accused of modeling on weightless strings and frictionless surfaces.)

So the gases hitting the Front of the device already caused a Rearward force on the barrel, then they hit the front and created a Forward force, but THEN they should bounce back again and press the barrel and device backwards. If there were no friction or dampening, this would go on forever. But it goes to zero in a very small number of cycles. Still, it is a contained environment and unless the force is moved sideways the front the rear forces "equal out" - but the key is that all that extra forward/backward motion takes enough time that the impact moment (we usually use the letter "J" for impact) is now delivered over a longer time domain - and that is clearly a big issue in perceived recoil. (And even the bouncy behavior describe above.)

35 years ago, I exited a career I did not care for: I wrote code for White Sands (WSMR) - I went there after grad school - it was a good job, but in the end, modeling nuclear explosions in computer simulations was not my dream career. All of the actions and reactions happening inside a rifle or handgun are simply contained explosions that really do follow the basic laws of physics. The behaviors are made more complex by the gaseous nature of the explosive results (or I should say byproducts) - but remember that more than 90% of the total recoil is caused simply by the actual mass of the bullet leaving the device forward and the equal-and-opposite-reaction rules take over. The bullet moving forward leaves with energy that is E=1/2MV^2 (The Kinetic energy is one half of the mass times the square of the velocity - and unlike Hook's law, there is no constant - the units of the equation net out to energy.).

And that force is delivered equally forward and rearward to make a net energy change of zero.

So all of the above thread is dealing soley with the remaining forward energy of the gases escaping and how they are handled.

Granted, there are some really clever people making end of barrel devices, but they don't get to change the laws of physics and the requirement of a net energy result of zero.

Ports that go sideways DO change the rules because of the energy redirection.

In the code I wrote for White Sands, (and this is legal to say publicly, I assure you) much of the early events were modeled in a state most people now call Plasma (which is not solid, liquid or gas) - but then, over time, the states transition from plasma to gas - and we were using equations very similar to those invented by Maxwell Boltzmann - in essence, entropy starts to dominate quickly in gases. It looks to me like one of the design features of the devices we saw in the video is to give shaped surfaces for the gases to interact. No offense to the guys building the devices, but I am guessing they used progressive experimentation rather than finite element modeling to arrive at their designs. (Not a bad thing.) Because they are using large chamber baffling (as opposed to tiny pin hole channels for example) we know that they are depending upon the randomness of gases to give them a lot of benefit (gases hate to be herded). But their design as far as I can tell is intended to deal primarily with sound energy, not the gases and the forces in the gases.

I know very little about the mechanical details of firearms - I am not a machinist or metallurgist. But the basic physics modeling happening is well within my wheelhouse. (I am not arguing from 'authority' here - I learned a lot about suppressors just researching the various points in this thread - and I certainly learned there are more kinds of devices than I have seen in LGS and on the range. And while I have never experienced the 'bouncy' behavior noted above, I instantly got it and realized there must be more going on that I have thought. In the end, the interactions are quite complex and have some real subjective results.)

Let's return to the kid in the box. But now let's do this:
- Put her on a perfect skateboard on a glass smooth floor
- Hand her a rifle with no device on the barrel
- Have her fire the rifle
She will move backwards 'n' number of centimeters (and we do need a perfect skateboard and frictionless floor for this)

Then put a side ported device on the rifle - fire again.

She will move back less because some of the energy was diverted in another direction.

Give her a non-ported suppressor - fire again.

She will move backwards the same amount as the first time, but perhaps at a slower speed.

Give her a spring and mass device (I listed one above) - fire again.

She will move backwards the same amount, but now, you will see her actually move back - fore - back and all a bit slower.

My motivation for writing all this is that the original question was probably intended as a practical question, but to me, it is about 'truth'. The model I am describing, the kid in the box, the kid on the skateboard, etc., is the best way I can describe the truth of what is going on here. In the absence of side ports, the backward energy will always be the same and any recoil change will be either heavier mass absorbing some of the acceleration, or the many 'spring' and 'baffle' effects that would slow down the delivery of 'J' to the shooter.
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Re: Do suppressors function as a brake?

#20 Post by YankeeTarheel » Thu Nov 01, 2018 4:52 pm

That is GREAT stuff, Max! I really learned a lot! You make a great point.

But I would add two things, the first with a caveat that I may not know WTF I'm talking about:
The bullet and gasses are external to the box and their motion and energy are manufactured outside "the box" which may change stuff.
The second is, as you point out, is the baffling. As the gasses bounce off the front and move back, they hit the baffles which absorb energy by deforming, and redirect those gases also to the side walls, which also deform and absorb energy. So instead of sending that energy back after it hits the front wall, gets absorbed and redirected. We saw in one of the vids where the deformation was sufficient to blow away the acrylic shell.

But it IS fascinating, isn't it?
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Re: Do suppressors function as a brake?

#21 Post by Marlene » Thu Nov 01, 2018 7:42 pm

Nicely laid out, Max. Yep. there is no reduction in total rearward energy. There is, on the other hand, a meaningful redistribution of that rearward energy over time. That's why a can makes it easier to keep your scope on target to spot your hits. That's why many people think of cans as effective recoil reduction devices.

Even with a $200 tax stamp, physics stays physics.
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Re: Do suppressors function as a brake?

#22 Post by YankeeTarheel » Thu Nov 01, 2018 8:01 pm

Marlene wrote:
Thu Nov 01, 2018 7:42 pm
Nicely laid out, Max. Yep. there is no reduction in total rearward energy. There is, on the other hand, a meaningful redistribution of that rearward energy over time. That's why a can makes it easier to keep your scope on target to spot your hits. That's why many people think of cans as effective recoil reduction devices.

Even with a $200 tax stamp, physics stays physics.
Ah, but the Orange Shit-stain can issue an executive order negating the physics! :lol:
If you tell the truth you don't have to remember anything." -- Mark Twain
My son says: "Don't argue with an idiot. They'll only drag you down to their level and beat you with experience!" -- YT

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