Reverse bullet legend

[USMC-03]

Originally Posted by Teejay9

Tranter, would this be comparable to a "dum dum" bullet? I believe they were outlawed in WWI. Wouldn't that work just as well, if they flattened the front end? TJ

My assumption is that with the typical hollow point round it wouldn't work. In this case the bullet is designed to expand in the human body and would be constructed of materials that are much less dense than the average AP or even FMJ round and thus essentially just "splat" on the armor plate. A hollow point bullet design may work well for penetrating light armor but it would need to be coupled with specifically engineered material.

[RunningOnMT]

Originally Posted by delta13soultaker

Yeah the steel core bullets of post WW1 would usually shatter on armor plate.

The Polish answer was to make a long 7.9mm cartridge based on the Mauser, but fired at much higher velocity. The bullet, they designed to flatten on impact. It retained 100% of its mass. Inside 100m, it would spall a 1" armor plate; inside 300m it could still spall 1/2" armor plate. The bullet was effected not very much by the typical armor slope found in the beginning of WW2. (Slope back then was < 30 degrees, unlike today where 45+ degrees is common.) In the beginning of WW2, the Polish used the weapon a lot against light armored Nazi vehicles and could kill a Panzer in urban terrain at close distance. When the Nazis beat Poland, they actually captured enough of those weapons to use on the Eastern Front against the Soviets, then the Soviets were so impressed with the rifle design (not the bullet) that they adopted part of it for their own 14.5mm anti-armor rifle.

The proliferation of heavy metals harder than steel successfully used to make penetrators, and the success at portable weapons that fired HEAT rounds, eventually made the technique obsolete. It is still a cheap and viable principle of armor penetration today. With some ingenuity, you could refit a resistance with rifles capable of killing APC's in urban terrain and without addition resources than what they already have.

Would the same principle apply to body armor ? In other words all other factors being equal, would a wad cutter bullet penetrate personal body armor better than pointed or round FMJ ?

[delta13soultaker]

Originally Posted by RunningOnMT

Would the same principle apply to body armor ? In other words all other factors being equal, would a wad cutter bullet penetrate personal body armor better than pointed or round FMJ ?

No, for several reasons.

First, that principle uses kinetic energy transfer to spall the armor; that is, it fragments the other side into lethal fragments. (It is not a very efficient mechanism really, compared to others. The projectile does not really ever penetrate the armor. A penetrator actually does, and generates a great amount of heat, along with spall too, so it does much more damage with less effort and usually a larger effective range.) Soft body armor will not spall.

Second, the kinetic energy transferred by self-defense handguns, even .357 Mag, is not even close to being lethal or enough to stop a man. A boxer can punch nearly twice as hard as a .357 Mag will hit a vest.

Third, this principle does not use penetration, therefor it wouldn't defeat a vest.

Fourth, many modern armored vehicles defeat spall by having crew compartments lined with kevlar panels hardened by resin. That right there tells you busting a SAPI plate this way will only get the fragments stopped by the vest behind it anyway, which is easy to see how.

So no, it wouldn't be effective.

[17thfabn]

I wonder, at what range would the inefficient ballistics of the backwards projectile lose enough velocity / energy that it would not work?

Early in World War II the anti-tank gun projectiles were basically just solid shot. It was found that often this projectile would skip off or shatter. So a cap was added that would help prevent the round from shattering, and glancing off. This was called armor piercing capped or APC. The cap caused the round to be less aerodynamic so another "ballistic cap" was added. The ballistic cap was aerodynamically efficient, and would shatter on impact allowing the projectile to go on it's merry way through the armor. This was called armor piercing capped ballistic capped or APCBC.

[delta13soultaker]

The Polish overcame the aerodynamics by externally designing the bullet in conventional shape, but that it collapsed flat on impact via its internal design.

[308 at my gate]

Originally Posted by Suwannee Tim

Alright, I will give you an example you can see. Find a pane of glass that has been shot by a BB gun. The part that is knocked out, a cone shaped fragment on the far side of the pane is the result of spalling. It is a well known phenomenon induced when a high velocity projectile hits a brittle material resulting in a relatively inelastic collision and high and sudden transfer of momentum. The angle of incidence has to be nearly normal, i.e. 90 degrees. The armor has to be relatively brittle, it will not work on ductile materials. The analogy to the punch press is correct. This phenomenon was exploited by the High Explosive Squash Head or HESH projectile. It is defeated by a number of methods including properly tempering steel plate so it is more ductile or using multiple layers of armor or sloping the armor.

So why would the same bullet that is shot forward or backwards not have the same effect. I understand your explanation of spalling but I do not see the difference in a bullet hitting metal having a different effect if both hit at the same 90 degree angle.

[delta13soultaker]

Originally Posted by 308 at my gate

So why would the same bullet that is shot forward or backwards not have the same effect. I understand your explanation of spalling but I do not see the difference in a bullet hitting metal having a different effect if both hit at the same 90 degree angle.

From the front, the bullet splashes I guess. Backwards they don't.