Perrazi boring

[Jim Wheeler]

So which dorm were you in at Hogwarts?

whahaha,,!  oops ! no  offence,,but funny !

 

[timps]

Ok let me answer the Physics side of it to really put the cat among the pigeons.

Before anyone jumps down my throat I have gone on record on another forum answering a similar question stating that I don’t think the difference will be noticeable by a shooter regarding the pressures used in shotguns but the physics behind it stacks up.

Recoil is in 2 phases that feel like one to the shooter, the initial jolt propelling the projectile down the barrel and then from the release of pressure once the wad leaves the barrel.  Now before anyone discounts this second pulse it is well documented and why muzzle brakes are used on guns when the pressure is very high. The projectile has left the gun so the only force they can be dissipating is pressure release.

Therefore, regarding shotguns if you create more friction by a tighter bore, abrupt forcing cone or tighter choke the pressure build up has to increase, this is an increase in potential energy plain and simple.

This potential energy has to go somewhere as energy cannot be destroyed only transferred due to the conservation of energy.  Releasing this greater stored potential energy  as the wad leaves the gun will push back on the shoulder with more force  Mr Newton again.

NASA use solid state rockets, nothing more than a tube burning a solid propellant with hot gases leaving this tube. The release of the escaping gasses is a measurable force and because of Newton’s law it will push in the direction of the shooters shoulder.

Now this is just an academic post so I am not saying it is going to knock your teeth out or you would even feel it, but it still can be measured and the sudden release of a greater pressure must equal greater force on the shoulder, whether this can be felt is a whole other subject.

So the physics isn’t wrong, just in my opinion the pressure increase is not significant enough to be felt by the shooter regarding the pressures we use with shotguns.  As I have no proof that it cant be felt I wont argue the point just proffer an opinion on that bit.

Now before I get accused of going to Hogwarts I do believe the moon landings were real so rockets work and muzzle brakes work on high pressure guns so I know the physics is sound.

 

[jwpzx9r]

Not that I am any great physics buff but I actually don't think so. The pressure is going to be a maximum at some point before the wad leaves the gun there after it is reducing so the maximum recoil will be evident when the pressure is at it highest value... that is going to happen before the wad leaves the barrel of the gun not after. I would have thought that the maximum recoil is due to the pressure of the charge over coming the inertia of the load. The actual expansion of the powder burning and becoming a gas has very often done all its expanding before the total volume of the barrel is filled in many weapons, don't know about a shotgun to be honest, but it has already been accelerated the load to huge velocity over a very short distance.

I actually don't think a solid propellant rocket motor can in anyway be compared to what happens in a shotgun barrel really other than that a solid is turned into a gas.

edit

This may or may not be pertinent to the analogy you are using but take this scenario. Take to identical cartridges in terms of propellant load but one has no load or wad  the other a 28g load skirt wad fire both gun back to back with the cartridges chosen at random...which of the two will exhibit the most recoil? I would say the cartridge with the 28g skirt wad would be the one the other would be greatly rudced by comparison so my inclination is that you won't feel the recoil by gases leaving that barrel of the gun after the wad has left  because as a component of the total recoil it is very small .

 

[Jim Wheeler]

So the physics isn’t wrong, just in my opinion the pressure increase is not significant enough to be felt by the shooter regarding the pressures we use with shotguns.  As I have no proof that it cant be felt I wont argue the point just proffer an opinion on that bit.

thats about right,, no one can eel the diffs im sure,,

I would have thought that the maximum recoil is due to the pressure of the charge over coming the inertia of the load.

also , about right, 

you can tell the difference between 19 and 36 gram lads,, fair enough,, but certainly not easy with a 28gm shotgun load,, having said that, there are variables, in wad, powder burn rate etc,, i have reloaded umpteen thousands of shells, 27gm, and as you increase speed from 1100 ft ps,to around 1450 or more,, the recoil will sharpen up, its a very complicated thing to share, but it is a factor ,, 

the other part of this is there is no need to suffer excessive recoil,, the quest for `speed` is not an essential,, the difference out on a 35 yard or 60 yard is negligable  as far as it goes, shot speed drops very quickly,, which is why you `think` the lead has increased,,but your allowing for speed dropoff,,, not the distance to target,,, unless trap shooting,,,

where you need to point at the target,, 

 

[timps]

Not that I am any great physics buff but I actually don't think so. The pressure is going to be a maximum at some point before the wad leaves the gun there after it is reducing so the maximum recoil will be evident when the pressure is at it highest value... that is going to happen before the wad leaves the barrel of the gun not after. I would have thought that the maximum recoil is due to the pressure of the charge over coming the inertia of the load. The actual expansion of the powder burning and becoming a gas has very often done all its expanding before the total volume of the barrel is filled in many weapons, don't know about a shotgun to be honest, but it has already been accelerated the load to huge velocity over a very short distance.

I actually don't think a solid propellant rocket motor can in anyway be compared to what happens in a shotgun barrel really other than that a solid is turned into a gas.

edit

This may or may not be pertinent to the analogy you are using but take this scenario. Take to identical cartridges in terms of propellant load but one has no load or wad  the other a 28g load skirt wad fire both gun back to back with the cartridges chosen at random...which of the two will exhibit the most recoil? I would say the cartridge with the 28g skirt wad would be the one the other would be greatly rudced by comparison so my inclination is that you won't feel the recoil by gases leaving that barrel of the gun after the wad has left  because as a component of the total recoil it is very small .

The maximum peak pressure is irrelevant for the 2nd recoil  it’s the pressure increase at the muzzle just as the gas is about to leave.  If the expanding is all done, then it would become a vacuum as the shot tries to travel down the barrel, the wad would then be travelling slower than the shot as its sucked back. What actually happens is the expanding is at a lot slower rate so the pressure drops but it is still exerting a force. People think it’s done and dusted because in the terms of added velocity to the shot down the barrel it is. In the terms of creating pressure due to the wad slowing or a blockage it’s not always.

It’s the change in momentum as the propulsion gasses suddenly accelerate a lot faster in the forward direction as the wad clears the barrel that causes the force at this 2nd recoil.

The greater the change in momentum the greater the force.

Force = (change in momentum) over (time taken).  

Slow the wad down and you slow down the escaping gas down, as the wad clears the change in momentum of the gas is greater as its starting from a slower speed than if the wad hadn’t slowed and the pressure would have increased thus creating more recoil force in the rearward direction. 

It is exactly the same as a rocket, it cannot be any different, accelerating gas leaving a tube is a rocket simple fact.  The gas has to accelerate once the wad clears the barrel, it doesn’t decelerate or stay the same so by Newton’s laws of motion it has to create force. Look up muzzle brakes and secondary recoil if you don’t believe me, but honestly it's exactly the same as a rocket there are enough articles on it. Change in momentum creates force this is the principle of a rocket.

Your analogy is correct but it bears no resemblance to what I am saying, having no load or wad would mean you don’t have the first recoil.

The first recoil is the change in momentum of 28g from rest to the required velocity in the time taken.

F=ma.

The second recoil is the change in moment of propulsion gasses from the speed they were going hindered by the wad to the speed they can now go not hindered by the wad in the time taken.

Force = (change in momentum) over (time taken)

Both forces are felt by the shooter as one, the gas is light but its acceleration (change in momentum / time) is high so the force is noticeable to the shooter, but not as noticeable as the first recoil.

In high powered rifles or artillery, they use muzzle brakes to deal with the 2nd recoil.

It’s explained like this; the first recoil exerts a force but the second recoil happens so quickly the shooter is still feeling the force of the first recoil when it kicks in.

First recoil is  10N the 2nd recoil is 5N total felt by the shooter as a perceived single pulse 15N.

Cause the escaping gasses to have a greater change in momentum the equation would be.

First recoil is  10N the 2nd recoil is 8N total felt by the shooter as a perceived single pulse 18N.

Shoot a high powered rifle with, then without a muzzle brake you would notice the difference; we don’t use muzzle breaks on shotguns as we shoot with a lower pressure but the physics is still the same.

 

[Oldblaster]

So which dorm were you in at Hogwarts?

Try not to ridicule things you don't understand, find someone to explain "over boring" for you! 

 

[ips]

my head hurts ....... a lot.

ps

I do not believe the moon landings actually happened, the whole idea is just silly. Just saying.

 

[timps]

my head hurts ....... a lot.

ps

I do not believe the moon landings actually happened, the whole idea is just silly. Just saying.

To prove my point on this you don’t even need to believe in the moon landings. Just buy a couple of bottle rockets on bonfire night then ignite the gunpowder contained in the cardboard tube of the rocket.

If the rocket leaves the ground then what I am saying is right, if they don’t move you have either bought crap fireworks or I am talking rubbish you decide.  

 

[ips]

I do not dispute anything you say, I have no idea.

merely saying as an aside that man did not land on the moon in the 60s when computers were the size of a small housing estate, colour tv was a dream and even captain beefheart (Don Van Vleit) could not have penned such a thing on an acid trip.

modern cars electronic wizadry is far from reliable and yet a couple of highly educated blokes chose to trust there lives in a rocket thing presumably cunningly fashioned from redundant Chrysler oldsmobile parts by a soon to be blue peter presenter.

one small step for man ..... one giant con for mankind.

anyway perazzi boring. ???

 

[Geordieboy]

 I've clearly stirred up a Hornets nest here 

I'm off to shoot the 2nd course of the worlds now.  After getting stuck yesterday for 4 hours in traffic and shooting really late and not getting back until midnight.........I'm off to do it all again!!!   :blink:

I'm Barmy!  :lol:

 

[ips]

barmy ..... Yes. You could have got into Glastonbury mud pit quicker than that. Twelve hour queue to camp in a mud pit listening to have been's and trying to be's making a god awfull din. What's that about ?

 

[Wonko the Sane]

Try not to ridicule things you don't understand, find someone to explain "over boring" for you! 

Tell ya what - you show me how 28ga, 20ga, 16ga, and 12ga recoil effects are measured as different for the same MV and same shot load in similar weight guns and I'll readily admit that Newton's Laws of Motion do not apply to guns.

and, TIMPS  you are presenting the classic example of a false analogy.  Not to mention some misunderstanding of fluid dynamics.

But all y'all have a great time believing what you like if it makes ya happy.

Slowing down the wad???  That's really an oldie but it never quits being funny

 

[timps]

Wonko please enlighten me where I am wrong I am happy to debate, if I completely misunderstand fluid dynamics then it shouldn't be hard to prove.

Not to sure why slowing down the wad is funny as trying to push a wad through a tighter constriction must ether slow the wad down or cause an increase in force needed to keep it at the same velocity due to the increase in frictional force resisting its momentum. Unless you feel a tighter bore or choke doesn't increase friction?

I believe what I feel I have proved, if someone tells me I am wrong they have to explain why for me to listen, just saying 'because it is' never worked when I was 6 so it isn't going to work now. Its not me being belligerent it's just how most in the scientific field are.

As I said in my earlier post I am not stating  a shooter would feel any difference at all, just the difference can exist even if it's tiny and can only be measured by really sensitive laboratory testing.  The last bit is enough for the marketing men if nothing else.

But as you say believe what makes you happy and I will believe what I think I proved.

 

[Wonko the Sane]

To tell the truth I don't even know where to start.  Nothing "slows" may be the best start.  Your assumptions are intuitive and counter to the usually applicable F=MA, not to mention contrary to the fluid dynamics of an expanding gas.

I just don't have the time for this and you can use yours to search the web for pressure testing info and researchers who have no vested interest in the gathered data.  That would be REAL data not some imagined conjecture or selected to support a beloved hypothesis.  Shouldn't take more than a few months for you to do that.  

have an nice day

Charlie

 

[timps]

Of course it slows Newton explicitly states this in his first law of motion.

"When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a net force."

In modern language.

Newton’s first law of motion states that a body will stay at rest or move with constant velocity unless a resultant external force acts on it.

Friction is an external force, push a bronze cleaning brush down your bore with no choke then do the same with full choke inserted. Applying the same force the brush will stop at the choke, you either apply more force or it slows to a stop. Force acts in both directions, just the friction when shooting is less than the force applied by the expanding gas but it has to be taken into consideration due to the conservation of energy. 

This is the fundamental bases of Newton's first law of motion, it's high school stuff.

I am fully aware of how an expanding gas behaves as I studied physics at college then later on in university. It expands as I have stated, we can debate that further if you like once we have got the laws of motion out of the way.

Pressure testing already done has no input on this unless it is taken at the exact time the wad clears the barrel with equipment sensitive enough and calibrated specifically to do that job. Something I doubt has ever been done. Peak pressure has nothing to do with this as the potential energy of the gas is still contained behind the wad and not been released.

How do I know what I say is true, it's simple,  as you rightly pointed out F=ma which when extrapolated also means  f=delta p over delta t  or as I put in plain language Force =(change in momentum) over (time taken)

If the gas accelerates it has to create a force  so when the wad clears the barrel it has to exert a force. 

You need to go back and understand newtons laws of motion a bit more than just F=ma you also need to read up on the conservation of energy. The potential energy of the gas released has to go somewhere and act upon something in an equal and opposite reaction it cannot be destroyed or just disappear.

I base this all from a pure physics standpoint ,if what I say is not true then Newtons law of motion is wrong and so is the conservation of energy.

As I have continually pointed out I don't think a shotgun shooter would ever feel the difference this was just an academic post. But my point still stands the physics stands up.

 

[Jim Wheeler]

oh, so what i said earlier is correct, it makes no difference to the recoil that you can tell.

which is why when i fart on the crapper, i dont go thorough the roof,,,so to speak,,,,

 

[timps]

The problem with all of this is when people claim Newton’s  laws and conservation of energy mean it cannot happen without understanding them.

Even the head-space argument has proof in physics with the impulse-momentum theorem. The time taken is the important bit in this little gem. It takes time for the cartridge case to move back but zero time for it to stop, seeing as the firing pin will push the casing forward it does hold water.

Impulse = Ft = mv – mu

I posted this on anther forum so excuse the figures but the point made is extending or decreasing the time of the collision will extend or decrease the impact force by the same factor.

In essence 0.1s to move the casing back but 0.01s to stop the casing dead as it hits the breach increases the force by a factor of 10. Time is a factor of Newton’s laws of motion and an increase or decrease time means you have to change the force accordingly. The energy is the same but the force different between the acceleration and the impact.

Force(N)     time(s)        impulse (N*s)          momentum change     mass kg  velocity change (M/s)

4000n          0.010            -40                           -40 kg*m/s                  10kg                        -4

400n            0.100            -40                           -40 kg*m/s                  10kg                        -4

As a scientist I have to accept the principle even though I might not feel the force for the simple reason in the analogy as follows.

Put a grain of rice on my outstretched hand, it applies a force due to its mass and gravitational pull. I cannot feel its force as its too weak but saying the force doesn’t exist or meaningless is wholly wrong. The reason being put a million grains on my hand and I will feel it, so if you say one grain is zero then a million grains must also be zero so to speak.

In the real world marketing men sell you sh*t that is one grain of rice by pretending that it’s a million.

But you have to accept the principle is sound in physics even though it may or may not be meaningless in real world situations.

 

[Hamster]

Regarding the head space argument I had my gun come off the face enough to see daylight between action and barrels but I hadn't noticed it myself because any extra actual recoil forces at play were easily cancelled out by the various factors used to reduce recoil in the first place such as the heavy gun weight, PFS stock, good pad, etc. After having the gun brought back to face using new discs (1 only as 2 made gun impossible to open) the gun felt no different to fire but was a pain to open and bugged me for ages until it wore in again.

Side by side guns where the head space issue was originally discovered are a different kettle of fish because they have so little recoil protection in the first place that anything added would have been noticeable, bear in mind the actions were never built to withstand volume shooting in the first place and most certainly much harder to re-build to new state. The guns were essentially too light for their common 30g loads, they usually had either poor or no recoil pads at all, the grip shapes being straight would have played no part in absorbing any rearward forces, short barrels would have accentuate flip, the stocks themselves were too thin on the face compared to modern OU standards, no recoil devices, etc, etc, so it's easy to see why people noticed recoil more when these came off the face.  

 

[Mutley]

The bore size and recoil has literally no effect, Krieghoff did lots of testing on this a number of years ago. What they did find was that the pattern efficency fell away sharply especially with 24g once above 18.7.

the testing was done, because a number of US shooters were using 10g barrels on a 12g chamber for American trap with huge success, after a lot of testing with european loads they binned the idea, it worked with 32g 1100 - 1200fps loads, faster and lighter loads just didnt pattern.

They also had some type of pendulum the gun attached to, to measure the recoil, it decreased with the really large bore tubes but the pattern was crap, so somerwhere in the depths of the vaults at Ulm, will be a load of odd barrels and something that lookes like a sextant...  

 

[ips]

my head really hurts now....