How exactly does the Schwarzlose feeds?

[RecoilRob]

[QUOTE="grampajack, post: 10666391, member: 239308". I've never seen any gun that even started to unlock before the bullet was out of the barrel.

.[/QUOTE]

Neither have I, but we aren't talking about a locked gun...it's a blowback or unlocked action. Let me ask a simple question: if a bullet weren't being propelled....would the barrel move forward? Consider a blank cartridge if it could be loaded with an enormous powder charge and then fired in both conventional and the blow-forward actions. Blowback could happen because of the jet effect and mass of powder ejecta creating the back thrust (or recoil) to move the slide back and the same goes for the normal Browning recoil operated action which could also theoretically function if enough gas could be generated and blown out of the muzzle.

Now the blow-forward action gets the same monster blank cartridge....and what is going to move the barrel? Friction of the gas going down the bore? This would be VERY difficult and certainly much, much less efficient than the other actions where the simple projection of mass was enough to generate the operating force. Here we need something else to grab a hold on the barrel to force it to move...and we conveniently have that in the bullet itself. So it stands to my reason that the friction of the bullet being propelled down the barrel is the motivating force that makes the blow-forward action work. It only imparts a small amount of actual movement while traversing the length of barrel due to the resting mass needing to be overcome, but it's enough to impart the inertia needed to then complete the operating cycle. Same as conventional recoil or blowback actions...some movement must happen before the propelling force is lost or the action won't cycle.

 

[grampajack]

Neither have I, but we aren't talking about a locked gun...it's a blowback or unlocked action. Let me ask a simple question: if a bullet weren't being propelled....would the barrel move forward? Consider a blank cartridge if it could be loaded with an enormous powder charge and then fired in both conventional and the blow-forward actions. Blowback could happen because of the jet effect and mass of powder ejecta creating the back thrust (or recoil) to move the slide back and the same goes for the normal Browning recoil operated action which could also theoretically function if enough gas could be generated and blown out of the muzzle.

Now the blow-forward action gets the same monster blank cartridge....and what is going to move the barrel? Friction of the gas going down the bore? This would be VERY difficult and certainly much, much less efficient than the other actions where the simple projection of mass was enough to generate the operating force. Here we need something else to grab a hold on the barrel to force it to move...and we conveniently have that in the bullet itself. So it stands to my reason that the friction of the bullet being propelled down the barrel is the motivating force that makes the blow-forward action work. It only imparts a small amount of actual movement while traversing the length of barrel due to the resting mass needing to be overcome, but it's enough to impart the inertia needed to then complete the operating cycle. Same as conventional recoil or blowback actions...some movement must happen before the propelling force is lost or the action won't cycle.

The inertia of the bolt/slide locks the breech in the case of direct blowback. I've not seen any firearm, whether it be simple blowback, short recoil, delayed blowback, etc; that even began to unlock before the bullet was out of the barrel.

Blanks would work just fine in the Schwarzlose, assuming you used a blank adapter. Again, the Schwarzlose is not fundamentally different than something like a PPK.

What you're suggesting is that the bullet gives the slide enough momentum to continue forward after it has left the barrel, but that's not what happens. The bullet leaves the barrel, then the slide moves. Momentum is mass times velocity, and at the time the bullet leaves the barrel there is zero velocity in the slide. Therefore there can be no momentum.

On a side note, short recoil is somewhat different from other systems. It's just Newton's third law. The barrel and slide are locked together and move backwards as one unit as a result of the bullet being launched off of the breech. It just uses the gun's recoil to move the barrel/slide unit a short distance, and then a cam unlocks the slide and it continues to move rearward. Note that this is all dependent upon the frame being fixed, which is why limp wristing will cause it to short stroke.

 

[lysanderxiii]

The inertia of the bolt/slide locks the breech in the case of direct blowback. I've not seen any firearm, whether it be simple blowback, short recoil, delayed blowback, etc; that even began to unlock before the bullet was out of the barrel.

With any blow-back (simple or delayed) the bolt/slide will begin to move before the bullet exits the barrel. In fact, the bolt/slide and bullet will begin to move in opposite directions at the same time (see Newton's Laws). It is just that the bolt/slide, being more massive (or delayed by a mechanical disadvantage), moves so much more slowly . . .

 

[grampajack]

With any blow-back (simple or delayed) the bolt/slide will begin to move before the bullet exits the barrel. In fact, the bolt/slide and bullet will begin to move in opposite directions at the same time (see Newton's Laws). It is just that the bolt/slide, being more massive (or delayed by a mechanical disadvantage), moves so much more slowly . . .

Like I said, millimeters. Maybe two at the most.

 

[RecoilRob]

What you're suggesting is that the bullet gives the slide enough momentum to continue forward after it has left the barrel, but that's not what happens. The bullet leaves the barrel, then the slide moves. Momentum is mass times velocity, and at the time the bullet leaves the barrel there is zero velocity in the slide. Therefore there can be no momentum.

.

OK.....if there is no momentum, just what mystical force causes the action to follow through with the cycle? There MUST be some momentum or kinetic energy imparted or it'll just sit there. The Laws of Physics don't allow for things to happen after the motivating force has ceased to exert its influence. Therefore if the action cycles....it had to begin movement while the bullet was acting upon it. (unless some external mechanism is employed such as a gas piston or the like)

Without a bullet being forced down the barrel, the Blow-Forward action will not function...so the bullet seals the barrel and then acts like a piston forcing it forward with the gas pressure within the case. Whatever force is required to engrave then push the bullet down the barrel also contributes to moving it forward....how can it not?

To say everything just sits there motionless until after the motivating force has left...just what Newtonian Law permits the action to cycle? What you propose violates all physical principals. And 'like I said...millimeters. Maybe two at most' per your last post is admitting that things DO move before the bullet leaves the barrel...which is what several of us have been trying to argue over the last few posts. You can't have it both ways....saying nothing moves but then hedging by saying 'two at most'. It either moves or it doesn't...and it does move.

 

[grampajack]

OK.....if there is no momentum, just what mystical force causes the action to follow through with the cycle? There MUST be some momentum or kinetic energy imparted or it'll just sit there. The Laws of Physics don't allow for things to happen after the motivating force has ceased to exert its influence. Therefore if the action cycles....it had to begin movement while the bullet was acting upon it. (unless some external mechanism is employed such as a gas piston or the like)

Without a bullet being forced down the barrel, the Blow-Forward action will not function...so the bullet seals the barrel and then acts like a piston forcing it forward with the gas pressure within the case. Whatever force is required to engrave then push the bullet down the barrel also contributes to moving it forward....how can it not?

To say everything just sits there motionless until after the motivating force has left...just what Newtonian Law permits the action to cycle? What you propose violates all physical principals. And 'like I said...millimeters. Maybe two at most' per your last post is admitting that things DO move before the bullet leaves the barrel...which is what several of us have been trying to argue over the last few posts. You can't have it both ways....saying nothing moves but then hedging by saying 'two at most'. It either moves or it doesn't...and it does move.

It works just like direct blowback. I don't know how else to explain it. With a blank adapter installed in the barrel, blow forward pistols would run blanks just like any other action. In essence, all semi autos are gas operated. It's just a matter of the empty case acting as the piston in simple blowback. Short recoil is slightly different, because the action is initiated by Newton's third law, being that the gas pressure is contained by the lockup between the barrel and slide. Once the cam unlocks the barrel from the slide, however, short recoil becomes direct blowback.

As for the effect of the bullet on the forward thrust of the barrel, it just doesn't play a part in the basic function of the action. The inertia of the barrel is greater than the force applied to it by the bullet at the moment it overcomes the static friction. If it weren't, then the barrel would immediately be thrust forward as soon as the bullet hits the lands.

 

[RecoilRob]

It works just like direct blowback. I don't know how else to explain it. .

Correct....it works just like a normal blowback action where the slide begins movement before the bullet leaves the barrel. You don't know how else to explain the unexplainable because it cannot be explained because it doesn't happen! There MUST be movement for there to be momentum and without momentum the action cannot follow through with the rest of the cycle. For some reason you are stubbornly refusing to concede this obvious point...so I'm done with this. Anyone who actually did have a question about how the blow-forward action works should have the answer by now.

 

[lysanderxiii]

Correct....it works just like a normal blowback action where the slide begins movement before the bullet leaves the barrel. You don't know how else to explain the unexplainable because it cannot be explained because it doesn't happen! There MUST be movement for there to be momentum and without momentum the action cannot follow through with the rest of the cycle. For some reason you are stubbornly refusing to concede this obvious point...so I'm done with this. Anyone who actually did have a question about how the blow-forward action works should have the answer by now.

Go back to your basic physics - draw a free body diagram of the frame (slide) and the barrel.

Gas pressure pushes the bullet forward and the case backward. The case will push the slide back as well. The barrel, because of inertia, will try to stay stationary, so there will be some relative motion between the barrel and slide. In addition, there will be drag between the bullet and the barrel, so the barrel will get forward motion from that as well, increasing the relative motion between the barrel and slide...

 

[grampajack]

Correct....it works just like a normal blowback action where the slide begins movement before the bullet leaves the barrel. You don't know how else to explain the unexplainable because it cannot be explained because it doesn't happen! There MUST be movement for there to be momentum and without momentum the action cannot follow through with the rest of the cycle. For some reason you are stubbornly refusing to concede this obvious point...so I'm done with this. Anyone who actually did have a question about how the blow-forward action works should have the answer by now.

There's nothing unexplainable about it. I've explained it backwards and forwards and from the side. I don't have any analogies left.

There are two things you don't understand. First of all, the action doesn't rely on any forward thrust generated by the bullet engaging the rifling. In fact, additional mass may have to be added to the barrel to counteract it, and/or the spring might need to be stiffer. The barrel is thrust forward simply by the gas pressure pushing against the empty case, which is held stationary by the breech. With the breech stationary, the barrel must move.

The second thing is that once the initial friction is overcome, the force needed to keep the bullet moving down the barrel is minimal. Imagine pulling a heavy sled. Once you get it moving, keeping it moving is relatively easy. That's the difference between static and kinetic friction. And the faster you pull the sled, the easier it is to pull.

The best illustration is imagining a barrel inside a pipe that is clamped in a vise, so that the barrel can slide freely inside the pipe. Now imagine there's a bullet stuck in the barrel, and you have to get it out without moving the barrel. If you simply push on it with the ramrod, you will push the barrel out of the pipe without moving the bullet. But if you whack it with a mallet, the bullet will move and the barrel will remain stationary, because the inertia of the barrel was greater than the force applied to it by the friction of the bullet moving in the barrel. So you can imagine what putting 20k psi behind it will do. That sucker will slide through there like greased lightning.

 

[lysanderxiii]

There's nothing unexplainable about it. I've explained it backwards and forwards and from the side. I don't have any analogies left.

There are two things you don't understand. First of all, the action doesn't rely on any forward thrust generated by the bullet engaging the rifling. In fact, additional mass may have to be added to the barrel to counteract it, and/or the spring might need to be stiffer. The barrel is thrust forward simply by the gas pressure pushing against the empty case, which is held stationary by the breech. With the breech stationary, the barrel must move.

The second thing is that once the initial friction is overcome, the force needed to keep the bullet moving down the barrel is minimal. Imagine pulling a heavy sled. Once you get it moving, keeping it moving is relatively easy. That's the difference between static and kinetic friction. And the faster you pull the sled, the easier it is to pull.

The best illustration is imagining a barrel inside a pipe that is clamped in a vise, so that the barrel can slide freely inside the pipe. Now imagine there's a bullet stuck in the barrel, and you have to get it out without moving the barrel. If you simply push on it with the ramrod, you will push the barrel out of the pipe without moving the bullet. But if you whack it with a mallet, the bullet will move and the barrel will remain stationary, because the inertia of the barrel was greater than the force applied to it by the friction of the bullet moving in the barrel. So you can imagine what putting 20k psi behind it will do. That sucker will slide through there like greased lightning.

One - the engraving pressure is substantial, up to 1500 psi, the amounts to a hundred pounds-force or more. Once the barrel starts moving forward inertia wants to keep it moving forward. Two - while the coefficient of sliding friction is lower, it is not zero. All it has to do is keep the force above the spring force, which is less than ten pounds.

 

[grampajack]

One - the engraving pressure is substantial, up to 1500 psi, the amounts to a hundred pounds-force or more. Once the barrel starts moving forward inertia wants to keep it moving forward. Two - while the coefficient of sliding friction is lower, it is not zero. All it has to do is keep the force above the spring force, which is less than ten pounds.

You're not taking into account the duration of the force. A greater force in a smaller time interval is what makes it work. It's like pulling a tablecloth without disturbing the dishes. You need massive acceleration.

Think about short recoil. If the engraving pressure were enough to play a major part in blow forward actions, then there's no way short recoil would ever work.

 

[tark]

The inertia of the bolt/slide locks the breech in the case of direct blowback. I've not seen any firearm, whether it be simple blowback, short recoil, delayed blowback, etc; that even began to unlock before the bullet was out of the barrel.

If that's the case why bother with the locked breeches at all?

The barrel is thrust forward simply by the gas pressure pushing against the empty case, which is held stationary by the breech.

OK, put a steel rod down the bore, with an empty case chambered, and push on the rod. Use all the force you want. Hit it as hard as you can with a hammer. The barrel wont move. The gas pressure isn't pushing on the barrel, it's pushing on the bullet.

Think about short recoil. If the engraving pressure were enough to play a major part in blow forward actions, then there's no way short recoil would ever work.

Something I had not thought about before. Food for much thought!

In fact, the bolt/slide and bullet will begin to move in opposite directions at the same time (see Newton's Laws).

When I first got on this forum, I maintained that I had never seen any auto pistol where the slide moved while the bullet was still in the barrel. Several links were quickly posted proving me wrong. I especially remember one of a 1911. It was a close up of the front of the gun and the slide began to move immediately. It moved less than a tenth of an inch before you saw the bullet emerge from the barrel, but it moved! I know by seeing with my own eyes that SOME auto's slides begin to move while the bullet is still in the barrel.

The best illustration is imagining a barrel inside a pipe that is clamped in a vise, so that the barrel can slide freely inside the pipe. Now imagine there's a bullet stuck in the barrel, and you have to get it out without moving the barrel. If you simply push on it with the ramrod, you will push the barrel out of the pipe without moving the bullet. But if you whack it with a mallet, the bullet will move and the barrel will remain stationary, because the inertia of the barrel was greater than the force applied to it by the friction of the bullet moving in the barrel. So you can imagine what putting 20k psi behind it will do. That sucker will slide through there like greased lightning.

This sounds to me like you just disproved your own theory. the mallet is equivalent to the powder's combustion and you just said the barrel won't move!! How does it move on the Schwarzlose? The pressures pushing the case against an immovable breech block are the same ones pushing on the bullet. There is no equivalent to the pipe, on the pistol.

If it weren't, then the barrel would immediately be thrust forward as soon as the bullet hits the lands.

Uhhhh....no. Because it weighs many times what the bullet weighs, it has enough inertia of rest to overcome being pushed forward, at least immediately...

I think I might have an answer. Has anybody measured the bore diameter on one of these contraptions? It might be a thousandths or two UNDERSIZED. On purpose, with a long forcing cone in the leade. (hope I spelled that right) This might provide the necessary friction for the bullet to pull the barrel forward. Kinda sorta....maybe.. I give up....

 

[zaitcev]

Has anybody measured the bore diameter on one of these contraptions? It might be a thousandths or two UNDERSIZED.

I don't think it was necessary undersize rifled barrels on blow-forward guns, as poor Royal Nonesuch once found out. The force of friction of a .50 BMG bullet against a standard barrel was enough to strip 1/8" off locking bars in one of his classic videos.

 

[grampajack]

If that's the case why bother with the locked breeches at all?

Weight mostly. When you get past .380, the weight needed to make simple blowback work is prohibitive. Even smaller calibers require quite a bit of bulk. Compare an LCP to a P232. The moral of the story though is that all breeches are locked in some way. With simple blowback, they're just locked by the inertia of the bolt/slide. Simple blowback could be thought of as inertia delayed blowback. And mechanical delayed blowback could be thought of as artificial inertia.

OK, put a steel rod down the bore, with an empty case chambered, and push on the rod. Use all the force you want. Hit it as hard as you can with a hammer. The barrel wont move. The gas pressure isn't pushing on the barrel, it's pushing on the bullet.

Even after the bullet leaves the barrel, there are still high pressure expanding gasses inside the barrel, pushing in both directions. It wants to escape any way it can. Think of it like a rocket taking off.

This sounds to me like you just disproved your own theory. the mallet is equivalent to the powder's combustion and you just said the barrel won't move!! How does it move on the Schwarzlose? The pressures pushing the case against an immovable breech block are the same ones pushing on the bullet. There is no equivalent to the pipe, on the pistol.

The same way direct blowback works. The barrel and breech move relative to each other, and the gas pressure is going to drive them apart. It doesn't matter which one moves, or in which direction it moves.

The analogy of the barrel in the pipe is to illustrate how acceleration can negate the effect of friction.

Uhhhh....no. Because it weighs many times what the bullet weighs, it has enough inertia of rest to overcome being pushed forward, at least immediately...

I think I might have an answer. Has anybody measured the bore diameter on one of these contraptions? It might be a thousandths or two UNDERSIZED. On purpose, with a long forcing cone in the leade. (hope I spelled that right) This might provide the necessary friction for the bullet to pull the barrel forward. Kinda sorta....maybe.. I give up....

Totally not necessary. You could have a blow forward using an oversized bore and it wouldn't matter, except it would reduce velocity and accuracy.

 

[RecoilRob]

https://en.wikipedia.org/wiki/Blow_forward

 

[grampajack]

https://en.wikipedia.org/wiki/Blow_forward

I would take wikipedia with a grain of salt. If you look at sources specific to firearms, they say it's a combination of recoil energy and friction that drives the barrel forward. There's zero doubt that the force of engraving provides some forward thrust, but my opinion is that that force has to be counteracted rather than being taken advantage of. This being that the force will be at its peak when the bullet hits the rifling, after which it will drop off to almost nothing.

If you research the development of blow forward at the turn of the century, they actually thought that the barrel would have to be tapered to make it work, so that the friction would increase towards the end, right before the bullet leaves the barrel and the action unlocks. That would prevent the action from unlocking too early.

 

[tark]

Weight mostly. When you get past .380, the weight needed to make simple blowback work is prohibitive.

Tell that to my Astra 400, or my 600. . The slides on both guns weigh about the same as a 1911 slide. It's the monster recoil and hammer springs that make it possible.

Even after the bullet leaves the barrel, there are still high pressure expanding gasses inside the barrel, pushing in both directions. It wants to escape any way it can. Think of it like a rocket taking off.

When the bullet leaves the barrel, the gasses are only pushing in one direction, straight rearward. You are correct about the "rocket effect" but it isn't pushing anything forward.

If you research the development of blow forward at the turn of the century, they actually thought that the barrel would have to be tapered to make it work, so that the friction would increase towards the end, right before the bullet leaves the barrel and the action unlocks. That would prevent the action from unlocking too early.

Maybe it IS tapered. Like I asked, has anyone actually measured one of these things?

I would take wikipedia with a grain of salt

BINGO! We are in absolute agreement on this one! I have seen many mistakes on their site.

 

[grampajack]

Tell that to my Astra 400, or my 600. . The slides on both guns weigh about the same as a 1911 slide. It's the monster recoil and hammer springs that make it possible.

Springs effectively create inertia (initially), but the problem is that the resistance increases as the spring is compressed. Real inertia effectively decreases as it gains velocity, making it initially difficult to move, but once in motion it's easier to add velocity in that direction. Once the bolt is set in motion by the initially high impulse, it wants to stay in motion, so once it's moving in the right direction it negates the increase in force as the spring is compressed. There's a really neat symbiosis in the relationship between bolt mass and compression rate in automatics. So the bolt is "unlocked" by the initial impulse, gains velocity even though the pressure is dropping as the bullet leaves the barrel, then has its momentum counteracted by the fully compressed spring so it doesn't create excessive recoil.

I've tried to conjure ways around that with ARs, but if you mess with the natural balance then it always decreases reliability. Every gun has its own balance, driven by the caliber and barrel length. You can get away with it for competition, and it works, but the result will never be reliable enough to use for defense.

With that said, I don't know anything about the Astra, but I hear they're very heavy. Like Hi Point .40 cal heavy.

When the bullet leaves the barrel, the gasses are only pushing in one direction, straight rearward. You are correct about the "rocket effect" but it isn't pushing anything forward.

The gasses are pushing in all directions. Think of the breech like a launch pad. If the launch pad is movable and the rocket is fixed then the launch pad will move (simple blowback), but if the rocket is movable and the launch pad is fixed, then the rocket takes off (blow forward). Again, that's why pistols only work if you keep a stiff wrist. Your hands are the launch pad, and you have to keep them fixed in place.

Maybe it IS tapered. Like I asked, has anyone actually measured one of these things?

Everything I've read says no. The original drawings talk about it, but it looks like there wasn't even a prototype ever made that way. It seems it was completely abandoned before the first prototype was even made.

 

[Jim K]

Sorry, but that rocket analogy is wrong. The rocket leaves the pad because the energy of the high speed gas coming out its back causes an equal and opposite effect on the rocket, overcoming its inertia.. The pad need not be there, except to support the rocket before firing. (Think the same rocket in space; the astronaut "floors it" and the speed increases, yet the launch pad is many miles away.; or the rocket as a rifle and the gas as the "bullet", with the recoil causing the rifle to move.) The bullet friction in the barrel is not significant; a shotgun charge has very little friction in the barrel, but my shoulder tells me that a 12 gauge kicks when I fire a heavy load.

Jim

 

[grampajack]

Sorry, but that rocket analogy is wrong. The rocket leaves the pad because the energy of the high speed gas coming out its back causes an equal and opposite effect on the rocket, overcoming its inertia.. The pad need not be there, except to support the rocket before firing. (Think the same rocket in space; the astronaut "floors it" and the speed increases, yet the launch pad is many miles away.; or the rocket as a rifle and the gas as the "bullet", with the recoil causing the rifle to move.) The bullet friction in the barrel is not significant; a shotgun charge has very little friction in the barrel, but my shoulder tells me that a 12 gauge kicks when I fire a heavy load.

Jim

That's true, but it helps to visualize what's going on. The thing with the gun is it needs the spent case to keep things pressurized while the barrel or bolt is accelerating. A rocket has fuel to spare, so it doesn't need that. Just imagine if the rocket were to be launched out of a tube initially, against spring pressure. If the launch pad were movable, it would move instead of the rocket. If the launch pad is fixed, then the rocket would move.

 

[tark]

that's why pistols only work if you keep a stiff wrist.

A lot of auto pistols work just fine no matter how limp wristed you hold them, including my aforementioned Astras. A 1911 with standard springs and hardball ammo will cycle just fine no matter how you hold it.

I don't know anything about the Astra, but I hear they're very heavy. Like Hi Point .40 cal heavy.

Actually, they both weigh 36 ounces, about the same as a 1911.

The gasses are pushing in all directions.

I dispute this. They are only pushing in all directions when the bullet is in the bore! Once the bullet is clear, that barrel functions like a rocket, with the muzzle being the exhaust end....and the only direction it is trying to go is rearward. Now the barrel cannot travel very far before the bullet exits, for obvious reasons, and once that bullet exits, the barrel is going to want to reverse course in a big hurry.

I've tried to conjure ways around that with ARs, but if you mess with the natural balance then it always decreases reliability. Every gun has its own balance, driven by the caliber and barrel length.

You got that right.! I have seen a lot of 1911s in my years with Les, that were damaged when somebody thought it was a good idea to put in heavier recoil springs. It may cushion the rearward motion but the slide would slam into battery with too much force. Cracked barrel lugs were the usual result.

That's true, but it helps to visualize what's going on. The thing with the gun is it needs the spent case to keep things pressurized while the barrel or bolt is accelerating. A rocket has fuel to spare, so it doesn't need that. Just imagine if the rocket were to be launched out of a tube initially, against spring pressure. If the launch pad were movable, it would move instead of the rocket. If the launch pad is fixed, then the rocket would move.

I'm gonna try this. I have a few model rocket engines left and a tube to put them in. An easy slip fit but not loose. Not sure what "against spring pressure" means, but I assume the rocket motor will be restrained by the spring from moving, initially.

 

[grampajack]

I dispute this. They are only pushing in all directions when the bullet is in the bore! Once the bullet is clear, that barrel functions like a rocket, with the muzzle being the exhaust end....and the only direction it is trying to go is rearward. Now the barrel cannot travel very far before the bullet exits, for obvious reasons, and once that bullet exits, the barrel is going to want to reverse course in a big hurry.

Think about this. Take an old single shot breech block rifle and remove everything that holds the barrel in place. It's going to launch about ten feet forward. Even if it's a slightly undersized bullet with no friction. You could even add enough mass to the barrel to where it would delay its launch long enough to keep the case from rupturing.

 

[Jim K]

"Just imagine if the rocket were to be launched out of a tube initially, against spring pressure. If the launch pad were movable, it would move instead of the rocket. If the launch pad is fixed, then the rocket would move."

It wouldn't make any difference as the launch pad plays no role in launching and isn't even needed except to hold the rocket upright. The reaction involves rear-moving gas and forward-moving rocket. Most folks think the gas "pushes" against the lunch pad or against the ground or against the air. It doesn't, it simply moves back and the reaction causes the rocket to move forward. It doesn't "push" on anything. Think of a space station in near-earth orbit with the engines turned off (normal condition). When the engines are fired up, the station moves in reaction, even though there is nothing at all out there for the rocket thrust to "push against."

Jim

P.S. On a smaller scale, think an ordinary hand-held rocket launcher, like the WWII :"Bazooka" and its successors. The missile sits in the tube; when it is fired, it moves. There is no breech block, nothing at all in the tube either ahead or behind the projectile. Nothing for the rocket or its propellant gas to push against. So it won't work, you say, yet it does, as many tank crews have learned to their very short surprise.

JK

 

[grampajack]

"Just imagine if the rocket were to be launched out of a tube initially, against spring pressure. If the launch pad were movable, it would move instead of the rocket. If the launch pad is fixed, then the rocket would move."

It wouldn't make any difference as the launch pad plays no role in launching and isn't even needed except to hold the rocket upright. The reaction involves rear-moving gas and forward-moving rocket. Most folks think the gas "pushes" against the lunch pad or against the ground or against the air. It doesn't, it simply moves back and the reaction causes the rocket to move forward. It doesn't "push" on anything. Think of a space station in near-earth orbit with the engines turned off (normal condition). When the engines are fired up, the station moves in reaction, even though there is nothing at all out there for the rocket thrust to "push against."

Jim

P.S. On a smaller scale, think an ordinary hand-held rocket launcher, like the WWII :"Bazooka" and its successors. The missile sits in the tube; when it is fired, it moves. There is no breech block, nothing at all in the tube either ahead or behind the projectile. Nothing for the rocket or its propellant gas to push against. So it won't work, you say, yet it does, as many tank crews have learned to their very short surprise.

JK

Okay, that's the PERFECT analogy right there, a rocket launcher. Imagine if you plugged up the exhaust. The tube would go flying backwards. You're right about the rocket not needing the launch pad to "push off of," but that doesn't change the fact that it is indeed exerting a force on it.

Scrap all that, though. I remembered a video I saw once of an M4 that failed due to galvanic corrosion. As soon as the bolt unlocked, the barrel was launched forward about five feet, leaving the rest of the gun in the shooters hands.

 

[tark]

Think about this. Take an old single shot breech block rifle and remove everything that holds the barrel in place. It's going to launch about ten feet forward. Even if it's a slightly undersized bullet with no friction. You could even add enough mass to the barrel to where it would delay its launch long enough to keep the case from rupturing.

Good idea! I'm gonna try that right now. I have an old Stevens Favorite take down model. When I unscrew the takedown screw the barrel slips easily in and out. I may get a ruptured case, but that's not a big deal with a 22. I'll fire it remotely with a towel draped over the action. back at ya in a few.