Action type and physics

[1911Tuner]

I certainly can't tell from that video when the bullet exits and any perceptible slide recoil happens.

Brother...If ya can't see it, it's because you refuse to see it. In the very last one...before the snub revolver...slide movement is clearly seen even before the initial blowby gasses escape.

If the bullet is gone before the slide moves, the slide won't move...at least not very much. While the exiting gasses and burned particulate have mass...it's not much mass. It's equal to the mass of the unburned powder charge. In the typical .45 ACP cartridge...that's about 5 grains. Even at a theoretical 4,000 fps exit velocity...which I think is pretty fanciful...that would amount to about 1/5th the recoil impulse generated by a standard velocity .22 Short. Not nearly enough to move the slide with the force and at the speeds that occur during the cycle.

The theories that you offered are impressive...and I'm not being facetious when I say that. I'd have accepted it if I didn't already know better, but you're making this thing way more complicated than it is. Recoil...and recoil operated...is nothing more (complex) than Newton's 3rd Law.

If the forces imposed in an action/reaction system are great enough to set both sides of the system in motion...they'll both move at the same instant. They don't have a choice.

 

[Oyeboten]

Very interesting...

1911-wise...

The Breech/Slide, and Barrel, moving as-one, begin to move, prior to the Bullet leaving the Barrel.

 

[1911Tuner]

The Breech/Slide, and Barrel, moving as-one,

Yep. The bullet is driven forward by the force resulting from the expanding gas. The slide is driven rearward by the same force...and because the upper barrel lugs are meshed with the slide's...the slide pulls the barrel backward with it. This is the locked part of "Locked Breech."

And...because the bullet's passage thru the barrel is exerting a strong forward drag on the barrel...the slide is resisted by that forward drag on the barrel. Of all the mechanisms that are delaying the slide in this...essentially a delayed blowback function...the bullet's influence is the major player. It eclipses the effects of all the others combined.

Other delaying mechanisms:

Slide mass.
Barrel mass...for a brief instant.
Recoil spring.
Mainspring.
Slide/frame friction.
Slide/hammer friction.

 

[General Geoff]

Another example is a battleship firing a broadside. Even firing all guns at once, a WWII era battleship suffers no displacement laterally from it.

Yes it does, just not noticeably so.


And to take your marble example further, if you hit the cruise ship with your marble, the cruise ship DOES get pushed back; just not in any meaningful way or distance.

Of all the mechanisms that are delaying the slide in this...essentially a delayed blowback function...the bullet's influence is the major player. It eclipses the effects of all the others combined.

Slide mass is THE most important factor in delaying blowback until safe chamber pressures are achieved, at least in a straight-blowback pistol such as a Hi-Point. This is why their guns are so ugly, because the slide has to be huge and massive to retard blowback. The 1911 locked breech design retards cycling enough that the slide can be made significantly lighter while still delaying the action from going out of battery before chamber pressures reach atmospheric level.

 

[1911Tuner]

Another example is a battleship firing a broadside. Even firing all guns at once, a WWII era battleship suffers no displacement laterally from it.

Sorry again, Oro. Not a valid argument.

It's not a prerequisite for both sides of the action/reaction system to move. If one side doesn't move, it's because the force wasn't of a sufficient magnitude to overcome its inertial and frictional resistance. Build a .308 rifle that weighs 200 pounds, and you can fire it without feeling a bit of recoil.

Go push on a house. You move, but the house doesn't...because you couldn't generate enough force to move it and because your resistance...either your inertial mass or by planting your feet...wasn't sufficient to utilize the force even if you could. That doesn't mean that the house didn't feel an accelerative force. It felt one. It just wasn't enough.

Back to the battleship with all guns firing. The reason that it didn't displace was because the combined recoil impulse and momentum from all projectiles and their velocities combined weren't of a great enough magnitude to overcome the ship's inertial mass and set it into motion. The ship "felt" a kick. It just wasn't enough of a kick to make it move. Lighten the ship enough, or make the projectiles heavy enough at the same velocities...or increase their velocities to a level that will generate sufficient momentum...and he ship will move.

Force forward equals force backward. Whatever force is imposed on one side of the system, an equal level of of force will be imposed on the other side. This is the heart of Newton's 3rd Law.

Again...

If the force applied is great enough to set both sides into motion...they'll both move at the same instant. They don't have a choice.

 

[General Geoff]

1911Tuner, in regards to the pushing of the house...

This is where elasticity comes into play. Regardless of the construction of the house, it will not move in one solid piece (unless it was built from a solid steel billet ). The point you're pushing on, will move far more than the rest of the house. The rest of the house will feel the tension on it from that point, but will generally not move because it is anchored by its foundation, which is anchored by the earth. Since you are ostensibly also on the ground, you're effectively pushing against yourself. This is why bulldozers don't move houses, so much as destroy them in place.

Now, if you took a rocket motor, and strapped it to the side of your house, and lit it, the rocket motor would not only be pushing the house, it would also be pushing the entire earth. Due to the earth's high mass and inertia, the rocket will not appreciably change the earth's rotational rate. But it will change it, to some infinitesimal, probably immeasurable degree.

 

[1911Tuner]

I understand elasticity, Gen'l. Tryin' to keep this question from devolving into an argument over semantics. I know the house moves. It just doesn't move enough for the human eye to detect it.

On the battleship thing again...if I may.

Assuming that all 9 of the ship's 16-inch guns fire at exactly the same instant...and that each projectile weighs 2,000 pounds. That's 18 tons of mass being accelerated. The USS Missouri weighs 45,000 tons. Without even considering the resistance offered by the water that the ship is sitting in...18 tons is a small fraction of the ship's mass. Expecting the guns firing to move the ship any appreciable amount is rather like trying to stop a train with a baseball bat.

Ain't gonna happ'n Cap'n.

And, no...Firing the ship's 5-inch guns with the main guns ain't gonna add enough to make a difference, either..

 

[General Geoff]

Hell, each turret weighs 1,700 tons...

 

[Oro]

Brother...If ya can't see it, it's because you refuse to see it.

Er, I'm looking straight at it and I can't see it:

http://www.youtube.com/watch?v=tiHTZzE1NdA&feature=related

It's possible there are different load levels being photographed; it's possible they are guns with different springs. I also think in the video above the gun is not in a fixed rest; because I think I see rearward displacement of the whole assembly (gun) before and rearward movement of the slide begins to take place. But since neither of us actually performed the tests and can swear and affirm to all the test parameters in each, it's best to just say the visual evidence is what it is and not try to defend some unknown persons undocumented work.

But classical physics certainly does NOT preclude getting a bullet out of a barrel before a blowback feed system starts to work.

Sorry again, Oro. Not a valid argument.

It's not a prerequisite for both sides of the action/reaction system to move.

I think you are agreeing by disagreeing? That was exactly my point and what my examples were trying to point out. But critically as the spectrum of possible and plausible examples allow, one side of the equation can move FASTER than the other, based on relative mass and inertia. That was precisely my point and what the cruise ship/battle ship examples were trying to illustrate.

18 tons is a small fraction of the ship's mass. Expecting the guns firing to move the ship any appreciable amount is rather like trying to stop a train with a baseball bat.

and 185 (or 200, or 230) grains is a small fraction of a slide and barrel assembly's total weight - 3.5%, to be exact (using 200 grains vs. a 19.5 oz slide). This is still relatively less than the weight of a South Dakota-class battleship's main-gun broadside, but still, the point is the same. Factor in how the impulse is delivered over time, and it's exactly the same point.

Slide mass is THE most important factor in delaying blowback until safe chamber pressures are achieved,

Geoneral Geoff, I agree with most your reasoning, but in this case make a test: it's spring tension. Place a slide on an auto without the recoil spring. Try to push it back with your finger. Then assemble it correctly with the spring in place and try it with your finger. Now make a "finger tip gauge" guess about which offers more relative resistance. It's the spring.

You can run the equations of elastic/inelastic equations with the slide and the bullet, but without factoring in the spring tension you are wasting your time - that's what my first post was trying to explain. This case is neither; it's a combination of the two types of "collisions" as classical physics calls them.

It's entirely possible, given the relative inertia of the slide and tension of the spring, to get a bullet out of a blowback firearm before the impulse momentum of the cartridge's recoil overcomes the inertia of the slide and spring and displaces them both backward. It's theoretically possible, it's mathematically possible, and there is photographic evidence to show it.

 

[General Geoff]

Geoneral Geoff, I agree with most your reasoning, but in this case make a test: it's spring tension. Place a slide on an auto without the recoil spring. Try to push it back with your finger. Then assemble it correctly and try it with your finger. Now make a "finger tip gauge" guess about which offers more resistance. It's the spring.

You can run the equations of elastic/inelastic equations with the slide and the bullet, but without factoring in the spring tension you are wasting your time - that's what my first post was trying to explain. This case is neither; it's a combination of the two types of "collisions" as classical physics calls them.

The finger tip gauge isn't really a good indicator of the forces at work here; a better indicator would be using a rubber mallet, and tapping the front of the slide. Pushing with your finger provides low but steady force (which is all that's needed to move a slide without a spring). Tapping with the mallet provides high but momentary force, just like firing a round (which will easily overcome the spring force, but the momentum will slow down the slide movement just enough).

The spring is not there to retard the action from going out of battery; it is there to return the action to battery. In order for the spring to provide enough resistance to sufficiently retard the action on its own (or mostly on its own), it would have to be so strong that the blowback force couldn't push the slide all the way to the rear.

As is evident from the video footage, the bullet leaves the muzzle long before the slide moves very far. After the point where the bullet leaves the muzzle, the force being exerted by blowback is zero. Why does the slide keep moving back? Inertia. The blowback force has already acted on the slide, and has started pushing it back. The ONLY thing pushing it back after the bullet exits the barrel is inertia. That is what overcomes the spring strength, sheer inertial force; not blowback. If the spring strength alone could retard the blowback force, the slide wouldn't budge at all upon firing.

 

[1911Tuner]

You don't see it because you refuse to accept what you're seeing. Everybody else sees it.

Watch closer. Pay attention to the end of the slide in relation to the left edge of the photo. Watch it get closer before the bullet exits.

The slide's spring tunnel moves closer to the dust cover before the blowby gasses appear. Watch it close, now...and accept what your eyes are telling you.

Even in the first video of the compensated pistol. The slide moves just a tick before the fireball appears in the ports. Because the fireball follows the bullet...it only stands to reason that by the time you see the fire, the bullet is well ahead of it, and the slide is well on its way.

And no...I'm not agreeing by disagreeing. One more time...If the force within the system is large enough to overcome the object's inertial and frictional resistance to acceleration...both objects will move at the same instant. They have to.

On the other hand, if one side can be moved by the applied force, and the other can't...then only one side will move. Go push on a house, and then go push on an empty refirgerator box. See the difference?

When you push...you immediately get pushed. If the bullet is gone before the slide moves, there's nothing for the force to push off of...no resistance to work the reaction side. Like frog-kicking in mid-air. You ain't gonna move far.

 

[1911Tuner]

Hell, each turret weighs 1,700 tons...

Now that you mention it...If I'm not mistaken, the ship's weight...displacement...is figured before anything else is added to the structure except the engines and props. Correct me if I'm wrong.

 

[Oro]

You don't see it because you refuse to accept what you're seeing. Everybody else sees it.

http://www.youtube.com/watch?v=tiHTZzE1NdA&feature=related

Feel free to dissect this video, but where is the rearward displacement? I just don't see it or hear anyone else saying they see it...

If I'm not mistaken, the ship's weight...displacement...is figured before anything else is added to the structure, except the engines and props. Correct me if I'm wrong.

Nautical "displacement" is figured a number of different ways - both dry, loaded (typical load), and "full load" (design limit), so unless it's footnoted or qualified, you can't know what is meant. It's very directly equivalent to load ratings on a truck - the vehicle weight, registered weight, gross weight, etc. A typical WWII US battleship (the "fighting" ones - the South Dakota/North Carolina class) would weigh around (estimated) 45,000 tons fully loaded with fuel/munitions/stores/crew.

 

[General Geoff]

Oro, look at the bottom of the video, at the guide rod. Notice how it is NOT moving, but the barrel and slide are.



edit; also, that doesn't really look like a 1911 to me. The principles are the same though; judging from the barrel and slide moving as one initially, it looks like whatever the pistol is, it uses the same locked breech design as a 1911.

 

[1911Tuner]

Here ya go, Oro. This is a very old ordnance x-ray picture. Look at the bullet...and then look at the position of the barrel link. The link doesn't get in that position until the barrel has moved a 10th of an inch. Here, the barrel is almost at the beginning of the linkdown point.

Look at the lugs while you're at it. The slide is pulling on the barrel.

Yes. It's firing. You can see the outline of the bones in a human hand if you look carefully.

 

[General Geoff]

Heh, you can see some denser parts of the bones in the shooter's hand. Awesome picture, 1911Tuner.

 

[1911Tuner]

Geoff, you can even see the gasses and smoke in the barrel behind the bullet. Look at the difference in coloration of the barrel behind the bullet and in front of it.

If memory serves me...that picture dates back to 1916. Probably to settle an argument over whether the slide moves before the bullet exits. heh.

 

[General Geoff]

Also, going back to the battleship tangent: A technical essay answering: Do Battleships move sideways when they fire?

As an interesting side note, the Mark 7 50 caliber 16" naval guns used on the Iowa had NUCLEAR shells available, called the Mark 23; using a W23 warhead, the nominal yield was 15-20 kilotons. How crazy is that?? Makes that 280mm (11") nuclear artillery cannon look like a toy...

 

[1911Tuner]

Gen'rul...That was excellent! I didn't even factor in the guns' elevation. I assumed horizontal...and even that wouldn't move the ship laterally very far in water. I'd venture a guess that the distance would be measured in fractions of an inch.

Also interesting that an Iowa class ship is 57,000 long tons...seaworthy.

At any rate...I'm havin' me a large time with this one.

Carry on!

 

[jerkface11]

Do you guys even know what blowback means??? You're getting it confused with recoil operated. A 1911 is a locked breach gun. It can't be locked breach AND blowback. Haven't you ever wondered why the barrel tilts on a 1911? That's the locking mechanism.

 

[General Geoff]

The locking breech mechanism is just an interim step to help retard the recoil operation. There's no reason why it couldn't technically be considered "delayed blowback."

 

[Oro]

Here ya go, Oro. This is a very old ordnance x-ray picture.

That is the most interesting and unique picture of a 1911 I have ever seen. I've collected a few in the last few years but that takes the cake. I have some professional training in radiology (albeit with a very different subject) so let me state what I see :

1) I see the lower lug is indeed off the link.
2) I see what I *think* is vertical displacement of the slide from the barrel because of recoil - it is evident both at the bushing and in the lug spaces.
3) I see rearward displacement of the slide relative to the barrel, not so much apparent at the muzzle but clearly apparent at the hood/breech interface.
4) I don't see any evidence of rearward displacement at the muzzle (I should), but I clearly see it internally and at the barrel hood as noted above.
5) The shooter has an incident of hyper-mineralization of the distal bone of the second phalanges. More tests are in order.

Since that's a "true" 1911 based on the radiograph, I'm guessing this is circa 1910-1920, meaning 230gr. and 825fps, 16lb spring. Given those parameters, the bullet is not out of the barrel and the slide is recoiling. Case proved. And with style.

I will note I hedged my statement above about recoil spring weights and bullet weights. This clearly shows that with standard rounds and springs, you will get slide movement before the bullet exits the barrel. (But it's fun to talk about battleships, isn't it?

And by the way - the North Carolina or South Dakota class were more than a match for the Yamato and Musashi - looks like you all googled up Langdorff or some of the other experts' work on large caliber ballistics. If you are interested in it, pm me and I'll send some more interesting links and historical work.

In case you think I'm being non-topical, the wide-spread use of STS steel during WWII for naval vessels is directly linked to the major advancements in firearms that happened in the '50s and '60s. US battleships of WWII and the S&W Model 60 in your pocket are directly linked.

Seriously though, that guy needs to see his doctor.

 

[Oro]

The locking breech mechanism is just an interim step to help retard the recoil operation. There's no reason why it couldn't technically be considered "delayed blowback."

+1 - that is how I've always read it to be defined. "Blowback" means the cartridge recoils against the breech to actuate cycling. It's pretty simple - the cartridge is "blown back" and makes the gun work. Delayed, rotated, direct, toggle, - all still blowback.

 

[General Geoff]

If you want to get REALLY pure on definition, technically all blowback mechanisms are gas operated, with the empty cartridge case still in the chamber acting as a gas piston pushing directly against the bolt face..

 

[Oro]

If you want to get REALLY pure on definition, technically all blowback mechanisms are gas operated, with the empty cartridge case still in the chamber acting as a gas piston pushing directly against the bolt face..

Dammit, I wish I'd thought of that. You are clever, aren't you?

That's so frackin' obvious - the cartridge is indeed a gas piston. You get the "Mr. Watson" award for the year.