Physics of penetration on a steel target?

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Hoxviii

Hoxviii

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Allright, I've had some results lately that are counterintuitive to me.

I have a 5/8" steel pendulum target that sits in my backyard and gets anything and everything shot at it. Pistol, rifle, doesn't matter.

The other day a buddy and I were shooting at it with rifles from about 75 yards. He was using a 30-06 and a .308 and I was shooting 7.62x54R.

Shooting the target with x54R with LPS rounds (steel cored) were less than spectacular. it punched in the full 5/8", but left a bulge on the back of the target. I found a couple of the steel cores, they look like a 3/32 welding rod with a 3/16 ball bearing on the end from where they hit the target and mushroomed.

FMJ surplus rounds from the .308 had identical results.

However, Remington 30-06 180 grain soft points and my x54R "surplus duplicate" handloads with 150 grain soft points punched clean through the target.

Anyone have any idea what's going on with this?
 
interesting. a heavier, soft bullet goes through the plate, where a hard bullet bounces off. kind of not quite what you would expect is it? i would think that the soft bullet would just break apart. did it by chance hit the same spot where another bullet had already streached and weakend (crater) the plate steel?
 
Speed. Speed (velocity) is the most important factor by far in the penetration of thin, very hard targets such as steel plates. The faster the bullet is going, the more energy that is converted to heat when the bullet hits and essentially becomes a very hot molten metal fireball which burns its way through the target.
 
I agree with the Doctor. Compare the ballistics on the two rounds and you should find your answer. Maybe has to do with the harder rounds, jacketed and steel core, being more apt to bounce off the steel; while the lead bullet is softer by nature and heat and so has more of a tendency to bore through rather than deflect.
Just my .02 cents, physics is fun!
 
there is also another thing going on here, which i am not qualified to speak on; but you have a molten action that is going on, with the two soft bullets, that as they hit the target, they apply a molten action that continues to try and push, and push , and push on through, and this action also happens on the surface of the target, beginning to 'moltenize' the spot where the bullet is impacting.
Is therer still a bulge on the target as it goes on through? if so this is happening partially becuase of the molten type action that is occurring on the face of the target; stretching it, as it softens and gooeys up, until the bullet pushes on through.
 
I sincerely doubt that 180 grain bullets from the 30-06 were moving faster than 150 grain FMJ surplus from the 308.

If I were a betting man I would say that it has a lot more to do with bullet construction than velocity.

7.62x54R, 30-06 and 308 are so simliar in the ballistics department as to be the same in this example excluding bullet construction.


I find it a little surprising that the soft points exhibited better penetration, but the corollation evident in this test is that FMJ and steel core ammo doesn't go through, but soft points do.

Absent a chronograph, and some side by side testing of identical bullets at varying velocities, bullet construction is the logical conclusion.
 
Back not quite sixty years ago, my father, my uncle and I were messing around with '06s, shooting at a piece of 3/8" WW II armor plate.

M2 Ball GI loads would make a crater but not go through. My father's 150-grain Hornady Spire Points blew on through, as would my 150-grain Rem Bronze Point handloads.

Mostly, we figured it was a velocity thing.

As for 180s in the OP, I'd just figure that more mass equals more penetration...
 
The rounds that go through bulge the plate, but not nearly as much as the rounds that don't. And it's not like the bullets just fall out the other side- the metal is all petaled out on the other side.

Not having a chronograph is the issue- (that's the next thing on the list), my handloads should have been equivalent to or slower than the 147 grain steel cored rounds according to the loading data- however, the data didn't specify a barrel length. If the data was for a 20" carbine, i could be picking up an extra 250fps or so out of a 30" 91/30 making a WORLD of difference.

I guess the next thing to try is to take 5 of the surplus rounds and break them down into components and load the steel bullets over the same powder charge I'm using for the soft points- see if that does anything.
 
I've shot the same kind of plate . My results were similar .

7.62X39 steel core from an AK . Steel core stuck into plate ; no complete penetration .

.22.250 26" Bbl. Max Load of Varget with 55 gr. Winchester SP ;
Complete penetration , hole looked like I took a drill with a 1/2 inch drill bit
and drilled straight through .

Tried the 22.250 with 55Gr. FMJ Winchester boatail ; No penetration , bullet simply shattered , not even a dent . Same with 50 Gr. Ballistic Tip .

The only difference here is that the steel plate , that I shot , was mounted on some timbers , so there was no movement on it's part .
 
How about shaped charge effect.

FMJ rounds have the back end open to the lead whereas soft points are contained by a cup.

Just a thought.
 
Bullet velocity is a factor, but not the whole story. A moving bullet has a lot of kinetic energy. When it stops suddenly, that kinetic energy is transformed into heat. It is that heat that not only melts the bullet but also melts the steel plate itself.

If you look closely at the plate, you will see small globules of steel splashed up from the instant when the steel was actually liquid.

Since an ordinary bullet is also melted by the impact, it rarely penetrates enough to do any damage on the other side of the plate.

When an AP bullet strikes the steel, the heat again softens the steel, but the carbide core goes through the molten or softened steel and does damage on the other side.

The same transformation of kinetic energy into heat is what causes a rifle barrel to bulge or split when a bullet hits an obstruction in the barrel. The resulting heat softens the barrel steel enough for the powder pressure to swell the barrel at the point of impact.

Jim
 
the formula for Kinetic energy is KE = 1/2 M X VELOCITY SQUARED. slight change in velocity makes a bigger difference in KE than slight change in mass.
 
did it by chance hit the same spot where another bullet had already streached and weakend (crater) the plate steel?
Click to expand...

Cratering the steel actually increases its yield strength. It's called work hardening.
 
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