At what velocity will a bullet puncture flesh? A Helmet?

Yes, there are numerous studies but all of them that I've read about did their testing fairly close to the muzzle, not extremely far off as the original poster first asked his question.

As far as falling bullets go, as they come straight down they will accelerate at the standard 32ft per second squared. Air resistance will provide an upper limit to this velocity. Thus if a bullet tumbles, it is slowed more by air resistance than if it remains point on. This latter bullet will be the most dangerous. I would suspect that even a rifle caliber bullet, falling from say 20,000ft, even if tumbling, could cause significant trauma to an unprotected head.

However, a bullet fired from the ground at a 45 degree angle on relatively flat terrain will be coming close to straight down as it reaches earth, but the top of its trajectory wouldn't be nearly as high as above. It probably wouldn't even go as high as 1000ft. Thus, it would have much less velocity as the one dropping from 20,000 ft.

 

Wow! No wonder you had to have your helmet on! I think these would be 40mm or above? Certainly not fired straight up either...so many rounds may have had some "ballistic energy" still...Ive often wondered about the casing AND bullets that are fired above London in the dog fights....imagine 6-8 .303 machine guns pumping out bullets and dumping casing above London...dont know if it would have been dangerous (certainly if the fighter was facing even a little downward - plenty of ballistic energy still there)...

 

Well - no; by definition, trauma medicine is more interested in the resultant damage to the body, not how far the bullet travelled to get there!

O god no! There was everything being hosed off! There was a lot of .303 from Brens on their odd AA mounts, Lewis guns etc in the hands of the Home Guard and Army as well as the guns of AA Command....and yes, obviously a lot of spent lead (and brass) courtesy of the RAF....as well as various German calibres!

Mostly that was what the lighter stamped-steel ARP and other emergency services helmets were really issued for - to be semi-protected in that environment. In a lot of books too, there's a suprising incidence of pics of cars and other vehicles with matresses etc. tied to their roofs!

 

Man...as if the bombs werent enough...you couldnt pay me to be behind a Lewis...bring a bottle (to keep me warm of course) and settle in ....wait for the hum and lights to go on...and settle in behind the Lewis...ahhh thats what dreams are made of...Doubt id hit anything, but id be a MUCH calmer person afterwards...

 

The International Wound Ballistics Association has done lots of study on this issue. Google Dr. Martin Fackler and see what you find. In general, it has been shown that at a velocity of about 250 ft/s (76 m/s), bullets can penetrate skin. And as regards bullets fired into the air not having the ability to wound when they return to earth, I call BS! Deaths occur every year around the world from bullets which were fired into the air. Google "celebratory fire" and you will find lots of them. Doc

 

Just to through a ball of yarn into this carefully knit cloth..............my dad always mocked an officer of higher rank that once chewed him out for doing something he was told not to do.....as many others did not having regular hot meals. They let go with temptation and yes used their helmets to heat water to have hot coffee or soup from time to time while in the Pacific. The quote he would yell out in command style as it was said to him, "Now you have done it, you heated the helmet and now the bullets will go right through! (referring to having removed the temper from the helmet, having used it as a pot over the fire). Yeah....how many foot pounds of force would it take to go through that? I have learned that several pellets of artillery powder for cannons was sometimes used even in Vietnam for a very available heat source for heating your coffee, easy to light as well.

 

No. Another quote from the link I posted...

"For larger calibers the bullet terminal velocity is higher since the bullet weight is greater in relation to the diameter. Major Julian Hatcher in his book Hatcher’s Notebook estimates that a 12 inch shell weighing 1000 pounds and fired straight up would return with a speed of 1,300 to 1,400 feet per second and over 28 million foot pounds of striking energy."

I really recommend that folks read the article at the link & google Julian Hatcher. Also see... Celebratory gunfire - Wikipedia, the free encyclopedia
Not all of these case are a result of falling bullets but they do illustrate what indirect MG fire could do.

 

How high can a machine gun actually elevate for indirect fire? Obviously it varies with the mountings, but I can't imagine the highest is anything like say a howitzer. As I understand it the machine gun has to be locked in elevation and azimuth in order to deliver reasonably accurate indirect fire in full auto. Anyway, the angle at which the bullet comes down will be bit steeper than the elevation, due to air resistance. Say it's fired at 20 degrees and comes down at 30, I expect most of the energy at that point is the remainder of muzzle velocity.

 

Our MG3 has a danger zone out to 3.600meters and i believe that the poodleshooter MG´s (.223) have around 1.200 to 1.300 but i may be wrong. So with the correct angle it creates a really huge aera of danger.

 

Huh? weight isnt a factor when determining a "falling" terminal velocity...if it has no "extra" energy, then its using "stored" energy (stored as it went up) - gravity...the only factor that effects this is shape...or in other words drag...if you are talking horizontal terminal velocity - doesnt exist. if that shell is fired straight up and loses all its ballistic energy then it will simply fall back to earth at a standard speed, its shape all that effects whether it slows...it certainly wont fall back at 1300-1400 fps! wheres the energy for that??

 

I'm merely quoting Hatcher. My understanding is that the greater an objects ratio of density to surface area the greater it's resistance to the effects of drag. A .50 cal. bullet is twice the diameter of a .25 cal. bullet yet it's weight is more than 4 times greater.

 

Assuming the bullets are of similar design, the .50 has eight times the mass of the .25 and four times the surface area. The ratio of mass to surface area/drag for the .50 is therefore twice that of the .25.