That last part is bullshit. If the force distributed across the plate were enough to break bones, then firing the rifle would dislocate the shoulder of the shooter.
The momentum is the same, the impulse (and therefore forces) are very different. The bullet is propelled down the barrel gradually - the force is spread through the entire time it takes the bullet to travel the length of the barrel, the reaction forces are applied to the stock gradually, and spread over the area of contact between the shooter and the gun.
A bullet stopped by a vest/plate has a much larger impulse. The bullet needs to be stopped essentially immediately, rather than gradually slowed down over a length equivalent to a rifle barrel, otherwise it kills you. The force is also more concentrated, occuring over the cross-sectional area of the bullet, rather than over the entire contact surface with the rifle.
Just because a plate stopped a bullet, doesn’t mean the plate then distributed that force evenly across it’s whole surface. The bulge on the back side of an impacted plate doesn’t form gently.
Backface soft armor also catches spall, which can be very dangerous itself. Even ceramic plates can have a danger of ceramic shards. I believe modern ESAPIs, XSAPIs, and such modern plates are designed stand alone, but original SAPIs carried a warning that their rating was only in conjunction with soft armor.
That last part is bullshit. If the force distributed across the plate were enough to break bones, then firing the rifle would dislocate the shoulder of the shooter.
Okay, neat. Fire a rifle with the stock held just in front of your floating ribs instead of welded to your shoulder and get back to us.
The momentum is the same, the impulse (and therefore forces) are very different. The bullet is propelled down the barrel gradually - the force is spread through the entire time it takes the bullet to travel the length of the barrel, the reaction forces are applied to the stock gradually, and spread over the area of contact between the shooter and the gun.
A bullet stopped by a vest/plate has a much larger impulse. The bullet needs to be stopped essentially immediately, rather than gradually slowed down over a length equivalent to a rifle barrel, otherwise it kills you. The force is also more concentrated, occuring over the cross-sectional area of the bullet, rather than over the entire contact surface with the rifle.
In modern body about it’s spread over the area of the entire 8lb plate, which is way, way more area then the butt of the rifle.
Just because a plate stopped a bullet, doesn’t mean the plate then distributed that force evenly across it’s whole surface. The bulge on the back side of an impacted plate doesn’t form gently.
To add to your point, trauma pads exist to help mitigate this. Blunt force trauma is no joke.
Backface soft armor also catches spall, which can be very dangerous itself. Even ceramic plates can have a danger of ceramic shards. I believe modern ESAPIs, XSAPIs, and such modern plates are designed stand alone, but original SAPIs carried a warning that their rating was only in conjunction with soft armor.
Maybe on a plate from 1965 that is just a sheet of steel inside cloth. Modern ceramic plates spread the energy of the impact.
Here’s a video of a Level IV plate taking a 30.06 AP round followed by like 6 5.56 AP rounds and a 7.62x54R AP round so powerful it jammed the rifle.
There’s no significant plate bulge even after all of that.
https://m.youtube.com/watch?v=D1qLZwBeMuM