Case Shot?

Sorry Tony, I'm still not seeing it. Here look, at 25000rpm a piece of shot at the outside of a 105mm has a linear velocity (and therefore on release an effective radial velocity) of appox. 137m/s (alright it should be a bit less since the radius is less by the thickness of the case and half the diameter of the shot, or width if it's not cylindrical), another piece of shot situated halfway from the centre is still rotating at 25000rpm but is linear velocity is only 68m/s (unsurprisingly half that of the previous example), and as you said at the centre angular velocity is the same, it's still rotating at 25000rpm but it's linear/radial velocity is zero. So the radial velocity and therefore dispersion is proportional to the shot's placement within the case which is also linear, and so should result in an even spread of projectiles, not one with them all bunched up at the outside with only a few in the centre.

Yeah, I know, I've used rat shot from a .22. It's rubbish beyond 5m. 12 Gauge is much better.

Edit: sorry buggered the units. long day.

 

I think that in practice, probably none of the shot will be exactly on the centreline of the canister, meaning that they all get thrown sideways to varying degrees, leaving a hole in the middle...

Tony Williams: Military gun and ammunition website and discussion forum

 

Yes, probably in practice. But that there should still be a fairly even spread across the entire pattern was my main point, since I don't see why it wouldn't have a linear distribution. And if there is a hole in the centre it is unlikely to be larger than the gap between every other adjacent piece of shot.

 

I think you lost me.....


It would be a generaly even spread but the centrefugal (sp) force would prevent most if not all of the shot to go in a straight line in relation to the barrel axis. Newton Third(?) Law where an object, if in motion, will always traval in a straight line unless acted upon by the ever present external force (damn, I sound smart )

 

Here this might be a little clearer. Velocity based on 25,000 rpm. some rounding errors may apply.

The actual pattern should be determined by the way the shot is packed.

 

What your example seems to omit is the fact that there are vastly more shot in the outer layers, very few in the centre. The further out from the centreline of the canister, the more shot there are.

Tony Williams: Military gun and ammunition website and discussion forum

 

Well of course it's omitted, it's unimportant, would take a lot of time to calculate their proper location and draw them all, it would result in a very large image, and it wouldn't demonstrate what I'm getting at any better that this one does, and probably be hard to see. I will if it is really really really necessary, but you'll have to provide me with some information on how the canister is packed.

Yes, there is more shot in the outer layers because there is more space for them there. As they disperse, they disperse both vertically and horizontally and so the area that the outer shot covers increases proportionally and the spacing (proportionally) remains the same.

Still no doughnut.

 

Here, for one quadrant only, velocity lines are to scale.

As you can see there is some rotational distortion as each projectile is moving slightly differently. But there's no bunching up towards the outside, and the larger number in the outer shells have no effect wrt a doughnut pattern.

 

<shrug> then if your calculations are correct, the conventional wisdom must be wrong.

Tony Williams: Military gun and ammunition website and discussion forum

 

Ok, after getting me up out of bed last night to try and figure this out........

I've reached a conclusion that the shot pattern depends on two main factors
1. Wether the gun whihc fired the shell is a rifled barrel or a smoothbore
and
2. Where the explosive is placed in the shell (considering the shot can be kept in the shell for a time before impact)

Fired from a smoothbore:
Because there is little or no retation initiated by the barrel itself, the shell does not spin a whole lot (assuming they don't rifled the individual shells)
Thus: The spread of the shot does not form a dougnut shape

will be back

 

That ammo was used much b4 wwII,in old muzzle load canons.

 

As grape shot I'm guessing?

Anyway, bell went for class.....

Now, a rifled barrel spins the shell creating the centrifugal effect whach acts on every indivudual peice of shot (we already knew that)

And as Gryle mentioned above the further the shot is from the axis of rotation the more velicity it has as it spins away form the A of R.
But, since it is next to impossible for any one peice of shot to be entirely balanced around the A of R all the shot will be flung outward. This creates a 'void' along the A of R thus creating an doughnut shapeed spread.

As to the placement of the charge to break the shell, if it were in the middle it would increase the outward velocity of the shot when it explodes.
If it is the nose of the shell (thus using the drag on the shell fragmants to rip the rest of it apart) it would create a shockwave that would reduce the shot's penetration ability (something like that anyway)
If it's in the base of the shell it would move the shot foreward faster (don't ask, it was late)

so.....who wants to be the first to shred my excessively flawed logic? :lol:

 

Well just remember you did ask

Look at the second image I posted. Yes, chances are that there will be no shot at the exact centre of the bore of the gun and so when spinning will have some radial motion leaving a void at the centre. However this void does not change the overall outcome, the pattern is full of such voids and due to the different effective radial velocities the pattern scales. For example piece A at the edge may be moving at 100 m/s and piece B half way out will only be moving at 50 m/s, after 1 sec they are at 100m and 50m respectively, at 2 sec 200m and 100m, B is still half way between the point of release and the edge of the pattern.

There are some additional forces at work but I can't see that they would radically change the pattern (outer layer shot has a higher total velocity than the inner, each individual shot on release will continue spinning around it's own centre of gravity, etc.).

 

case and grape

for ML cannons they used to have both case shot and grape shot. grape was usually loaded on bags with a pusher plate and were often in the 1 to 2 inch size. case [ or canister] was musket balls loaded in a thin tin container with a wooden base. case was used at close range [ under a couple hunderd yards or so] for self defense from charging troops. grape was used at longer ranges and had a useful antimaterial ability as well. shells were used at longer range and were made both with and without musket balls as part of the load. shipboard caronades fired shells but were short ranged compared with guns.