Sorry Aliwa. Hate to do it to you, but in being right, you are also a bit wrong. Rocket thrust is nothing more than recoil. Generaly at quite a bit lower pressure than a freshly uncorked high powered rifle bore, but it's still an unbalanced reaction to pressure, and it's momentum is equal to the mass and velocity of the ejecta. And it is the same principle upon which muzzle brakes and thrust reversers work.
As I recall, the limiting velocity for the escaping gas from a rifle bore is in the neighborhood of 6000fps. For some reason I want to say that refered to a 30 cal, bore, but I'm not positive. The limit on bullet velocity seems to be in the 5000-5200fps range, so a bit faster than that would be normal.
We could take the following example and micro-engineer the dog squat out of it, but it'd get way too complex. So I'm going to address it in fairly large generalities.
Let's assume that we have a 200 grain bullet, in front of 50 grains of a powder that launches it at 3000 fps from a 26" barrel. (This is just to set up the math - the values can be changed later to fit any particular load you have)
Bullet data
200*3000= 600000 grain-ft/sec
Gas Data
50*6000=300000 grain-ft/sec
So a full 33.3% of the recoil is due to the ejected gas
(granted not all of that portion is felt at the exact same time, but we'll get to that - before the bullet leaves the barrel this portion is "only"
50*1500=75000 grain-ft/sec or 11% of the total recoil impulse)
We've been using the assumption that the average velocity in the barrel is the average between the intial velocity and the muzzle velocity, or
(3000-0)/2 = 1500fps
I know that this is way conservative on the slow side because the bullet is traveling much faster than that by the time it gets to the 13" mark. But that fact causes the "time in barrel" number to be a lot smaller and that causes a few things to show up that really scare some folks, so we'll stay with the conservative figure for now.
At the point where the 200gr bullet has gone 26", and the 50 gr or powder gas has gone 13" (some has gone 26" some hasn't moved, and there is uniform pressure through the bore) The rifle has generated some 670000 grain-ft/sec of...well data at this point.
The cumbersome problem of dealing in feet and inches here is the problem of getting grains and pounds into a unit of mass. The Imperial unit of mass is the Slug - and it is the unit ones need to use (unless you like flip-flopping to metric and back for the conversions - which is just as bad)
There are 7000grains/lb, and 32lbs/Slug, (224000 grains/slug)
and a Slug-ft/sec/sec is a pound force. (grains/224000)
* 32ft/sec/sec = pounds force
Some folks may notice that there aren't enough "seconds" factors to come up with pounds force yet...And we haven't. We need a figure for the acceleration that got us to 3000fps - which is where the "average velocity" come in.
If our "average velocity" was 1500fps, and our barrel is 26" long - our time in barrel was 0.001444 Seconds.
So our momentum is (670000 grain-ft/sec)/0.001444 seconds
(670000/224000)Slug-ft/sec/0.01444sec.
or 2086.26 (.259248 rounded) pounds of force - double checked.
Some will D A M N that's a lot...Yes it is. However look at how far that has moved our (let's say 9 pound) rifle in that time.
F=MA or A=2086.26/(9/32) (It's that mass thing again)
A=7417.8 Ft/sec/sec (232 Gs or there abouts - and you wondered why scopes slipped)
Distance=Velocity*time=1/2At^2
So 3708.9 *0.001444 *0.001444 =0.007738 feet
0r 0.093"
Up to this point it didn't make any difference if you had a brake or not, as the bullet has not uncorked the barrel.
Any questions?
You're doing it to yourself. I know. I'm discovering that I must be an absolute glutton for freaking punishment.Ohhh vibe, you're not "doing it to me" my man!
The duration of the pulse is really not relevant to the physics, other than it makes some of the resultant numbers a bit larger or smaller. But they are just numbers, and numbers do not change how your shoulder will look after 10 rounds of Earplittinloudenboomer.
For the most part a very efficient suppressor will follow the behavior of an inelastic collision, absorbing the forward momentum and energy of the gas it stops (or rather slows down drastically before releasing it as a much lower velocity).
Unless the cartridge is WAY overbore, a suppressor will not pull the gun forward with more force than the recoil, but it can reduce the recoil by a good 30% or better if properly designed and built. (too many factors here between device design and cartridge in question to be any more exact).
I did quite a bit of model rocketry as a kid. And I'm not going to claim to have read all of Heinlein or Asimov...But I used to have a sizable collection myself.
You're right rockets are slow. Because they are pretty low pressure...like your fireforming rounds. But have you ever seen any of the "shoulder fired" 20mm "Boys Rifles"? With the "Muzzle brake" exhaust pipe that extends to the rear of the shooter? Rocket arrest is about what that amounts to.A rifle is a mortar in pyro........ a rocket is, well, a rocket. Two entirely different ways to send a charge to altitude. Rockets is friggin' SLOWWWW dude...stopping a rifle with a rocket wouldn't feel so veryvery good.
al
And if you cup them enough so that they catch ALL of the water, and redirect it 180°, without splashing it...The scale will register TWICE as much as it will by simply stopping ALL of the water. Why?
Yes you can, and yes it has. But since this "exhaust" can be so damaging to the shooter when so directed, it had to be enclosed in an exhaust pipe that extended well to the rear of the shoulder stock pad. Makes for a very unwieldy assembly. But it apparently did as designed.
Unfortunately I have not been able to relocate any pictures or writeups on it now. It was years ago when I read about it. It was used on the (IIRC) the 20mm Anti Tank Rifles.
Thats because their design depends upon the gas impacting upon the plates as it passes through and they are attempting to redirect the "splash". If they would carve the gas away from the bullets path instead it would be much more effective. Something like the Reflex suppressors do.
Sound Level and Recoil
Even though the supersonic crack remains, the overall sound level is greatly diminished. The report sounds like a rapid hiss of compressed air as the slowed gasses issue from the muzzle of the suppressor. The suppressed .223 and .308 rifles become quite comfortable to shoot without hearing protection.
Since propellant gas is responsible for about half of a rifle's recoil, and since that gas is captured and released slowly, the recoil level will be about half that of an unsuppressed rifle. A .308 has a propellant charge weighing about 50 grains. This is of course converted to 50 grains of gas, and this gas only moves forward about 60 cm or 2 feet before the suppressor baffles intercept it. The fact that the gas doesn't leave the muzzle of the suppressor at high speed is responsible for much of the reduction in recoil. The interception of forward momentum (which results when that gas is captured in the can) is responsible for much of the remainder of the reduction in felt recoil. In addition, the weight of the heavy can on the rifle's muzzle acts as a pendulum, limiting muzzle rise and swing as the rifle recoils, and then pivots around the shooter's body mass.
MUZZLE BRAKES? RECOIL? All brands of Suppressor Project tested muzzle brakes increased the shooter's exposure by 5 to 10 dB. The increase in noise exposure is proportional to the recoil reducing effect of the muzzle brake. Replacing it by even a modest suppressor may thus produce a considerable 20 dB improvement at the shooter's position. This principle is valid for all weapons equipped with muzzle brake. Suppressors reduced recoil energy by 20 to 30 per cent, or about as much as muzzle brakes. They also prevented muzzle climb of assault rifles, firing full-auto bursts or continuous rapid fire. The page Suppressors and Shooting Range Structures page tells more about the topic.
We have said all of this about recoil only because many people have a hard time understanding how 50 grains of gas can he responsible for as much felt recoil as 168 grains of rapidly departing bullet. The answer of course is that the bullet, being heavy and inelastic, issues forth at a relatively slow speed when compared to the lighter and (we are told) perfectly elastic gas. Since energy is a product of mass times the square of velocity, it can be seen that the gas doesn't have to exit many times faster than the bullet to equal its energy. Empirically, we know that recoil from a suppressed rifle carrying a high powder charge is much gentler with a suppressor than without. All theoretical argument stops after that point. If a rifle hurts you to shoot it before suppression, it becomes quite comfortable to shoot after it's been suppressed.
What we have in the case of the act of reversing the gas flow is not so much a second impulse as it is a continuation of the same impulse. True the gas has already been accelerated, but it would continue upon the same line of motion if not acted upon by another force, which in this case is the fact that the muzzle brake vane causes it to change direction, the farther from it's original line it's forced to be diverted, the larger the force required to do it.
The problem here is that you are apparently picturing items of the same size, not the same mass. I say this because you could not be more wrong.
"Holy Cow!!! There's my answer!And transfering too much too quick is sometimes a very bad thing, which is why deadblow hammers are exactly what is called for in many situations. They do not impart the shock that the rapid high force application caused by a metal hammer would deliver. Our 50 grain stream of high velocity gas will not impart a shock either, anltough impingment erosion might become an issue.
Basicly I said a suppressor makes a fairly good muzzle brake.
But a reverse directing brake works better at reducing felt recoil.You should have stopped with "The beanbag simply transfers all of it's energy and momentum to the target and...."
al.
LOL. As do I my friend, and this IS the way it is.
) So far his thinking is basically his own. .... THEN he proved himself to be MY SON 