(post shortened)
Unless, of course, the bullet doesn’t clear the barrel before the rapidly increasing gas pressure causes a catastrophic failure of the barrel’s steel. It happens. :eek:
Centerfire rifle .308 M1A - http://www.thegunzone.com/m1akb.html
Side by side 12 gauge shotgun - ImageShack - Best place for all of your image hosting and image sharing needs
WWI artillary piece - http://thumbs2.ebaystatic.com/d/l225/m/mwm2nHCkvTDA6R5blToqkmw.jpg
It looks like the powder detonated, the bullet did not even engage the rifling, so friction was not a factor.
Blocked barrel, again friction wasn’t an issue. And shotgun pellets can’t get stuck in any case.
This looks very much like an obstruction in a barrel setting of an HE shell.
Interesting analysis.
The M14 was analyzed in 2001. The finding was that the steel used to make the after market barrel was not of the best quality. Several radial and horizontal cracks were found in the steel but the catastrophic failure began in the area adjacent to the bullets location (identified in Figure 4). The barrel split lengthwise and the barrel and receiver expanded left and right. The were no apparent defects in the receiver assembly but the receiver still blowed up real good.
The report makes for an interesting read.
http://www.thegunzone.com/m1akb/762r.html
The stage was set for the propellant’s gas pressure to destroy this rifle. Would this failure have occurred if the bullet had left the barrel, allowing the increasing gas pressure to safely exit the barrel?
The shotgun barrel failed because the expanding gas pressure exceeded the structural strength of the barrel’s steel. Was the barrel blocked? Was the wrong propellant used? Was the shot cup and pellets moving too slowly to clear the barrel before the steel failed? idk for sure.
The artillery piece may, indeed, have failed from an HE detonation inside the barrel. idk. (I thought the pic was too cool not to include it.)
Teardrop gives blunt rounded nose followed by taper to prevent flow separation, which causes turbulence and, thus, drag.
An interesting feature for arrows is the training effect. When firing the arrow, of course, the weight up front makes it “difficult” to fire because the push has to go through the center of mass or the arrow tumbles. However, after the push has ended, the arrow flies center of mass first. The tail is lighter and trails more easily, with the fins providing stabilization of the tail. This is the same way bottle rockets work - the tail trails the mass, and thus gives stabilization.
Like balancing a broomstick - trying to balance by supporting underneath requires a lot of effort and finetuning. “Balancing” the broomstick by holding the top only requires gravity.
Fin-stabilized projectiles are more like arrows or the aforementioned bottle rockets: Mass up front, long tail with fins to provide a trailing stabilizer.
I don’t follow. Are you saying the projectile mass can be longer?
Penetration, which is vital in defeating armor, is in part dependent on the momentum per cross section. A longer projectile concentrates more momentum per cross section, and thus aids penetration.
Are you thinking of Area Rule? That is specifically for winged bodies. It is done to compensate for increased cross section due to wings and is of no utility to a body without wings.
Not so much lengthening it for its own sake but for some reason. A boat tail reduces drag and cross-winds but you have to lengthen the slug to be effective. Gerry Bull’s primary breakthrough was finding a way to reduce the rear vacuum which significantly limited a projectile’s range. He made special “base bleed” projectiles with slow-burning powder at the rear to “fill” that tail vacuum. That way, he was able to extend the range of a 155mm field gun from 7 miles to 16 miles.
Right, but a large round lump vs a large round lump with a negligible tail is going to be about the same. I’m thinking a tail-finned sabot round looks like an RPG missile: big payload at front, thin tail with fins so they fit in the same cross sectional area. I would think the effect you are talking about would require a long mass, not a hollow tail.
googles boat tail, googles base bleed
The boat tail is the slight taper at the rear. This works the same way I discussed above about streamlining to reduce drag by reducing turbulence. As you point out, very low drag bullets are longer and thinner, with a boat tail.
Base bleed reduces the vacuum at the shell rear, which is a significant source of drag. It’s related to turbulence.
Think of it this way: as the airflow splits around the front of the bullet, you get drag from pushing air forwards/sideways. The forwards push pushes other air out of the way, etc. Then as the airflow streams along the bullet, it reaches the rear of the bullet. As it separates from the rear of the bullet, there is a pocket behind the bullet that has no air. Thus air has to move into that pocket. That pocket is the vacuum, and air trying to move into that pocket breaks the “laminar” flow coming across the bullet skin, creating turbulence.
Streamlining the tail curves the laminar flow along the surface, reducing the pocket behind the bullet and thus reducing the turbulence created in the bullet’s wake.
Base bleed is creating gasses at the rear of the bullet, filling that vacuum, so the streamlined laminar flow is less disturbed. However, there is then turbulence generated by the outflowing gases mixing with the laminar flow. The trade off appears to favor overall reduced drag, but it’s only useful for long range shells, because the improvement in performance is at the cost of payload mass to target.
I didn’t mean that the tail contributes significantly to the penetrator mass; I meant that it provides stabilization to a projectile too long and narrow to spin-stabilze. Most sabot cores (the projectile after the casing has been shed) look like long skinny darts. Here’s a typical example.
