On another forum there is a discussion ongoing about bullet penetration in steel. A couple of guys say that high velocity and small caliber, their example is a .223, will out penetrate something like a .308 in steel plate. The argument is that the smaller caliber offers less resistance to the steel plate and the high velocity is more important than the greater momentum and energy of the .308. Also that the greater diameter of the .308 works against it in such a penetration test. I can sorta go along with that, except it seems to me that the military usually lays down the 5.56mm for the 7.62 when they want more penetration against light armor. Right now I'm thinking about insurgents in Iraq using car bombs at roadblocks. From what I gather the 5.56mm SAW failed to chop up oncoming vehicles and disable them, so the roadblocks went to 7.62 weapons systems at such stations. I guess the .50 BMG would be better yet!

Second part of the discussion centers on a statement made by one of the paticipants that bullet construction does not matter in steel plate penetration. In other words, a highly fragile 55 grain varmint designed hollowpoint, or plastic tip V-Max, Ballistic Tip, varmint bullet in a .223 will penetrate as well as a FMJ (not steel core) or a strongly constructed controlled expansion bullet such as a Barnes X. This I cannot get my head wrapped around. That doesn't seem likely to me. Can someone shed some light on the subject?

Velocity is the most important factor in pentrateing steel,but a FMJ and exspecialy an armor pierceing round of equal velocity will out penetrate an expanding bullet of the same speed. A 30 cal bullet of the same speed and construction as a 223 bullet will penetrate steel equaly well..........

On my steel gong my 22-250 AI leaves a deeper crater with 50 grain Vmax, than my 30-06 with 165 Interbonds. There is about 900 FPS difference in velocity though.

Ah, yes... Would explain why military ball ammo is useless for hunting...

I would go with the bullet construction does matter argument - as long as its a soft bullet. Example: I have steel plates of varying diameters on chains at my Dad's range. The plate is 3/8" thick. We rountinely shoot at them off hand for fun. There are only 2 holes through them, I put both of them there with the same gun - a 300 WM shooting 180 Sierra's under a max charge of RE 22. Muzzle velocity ~ 3100 ft/sec. It appears that the high impact velocity melted a hole through the steel. I've shot the steel gongs with everything from 22 rimfires to 416 Rigby using all the major cup and core bullets plus most of the premium's. The 180 Sierra's are the only one that has left a hole.

Velocity is the number one factor for a hunting bullet. You can drive a hot dog through a steel plate if its moving fast enough - pure physics you don't want me to explain.

Sectional density is just as important in steel as it is in flesh and bone. MD tests have shown that equal SD's penetrate equally, regardless of caliber.

Hardened inserts in a bullet have effect of keeping the momentum forces linear as opposed to deflected. A soft bullet needs to go faster than a hardened one to penetrate equally.

Caliber by itself inhibits penetration. It is easier to push a needle through something than a 1" punch. A 308 of less SD than a the 22 needs to go faster (relatively) to penetrate equally. A 22 with less SD than the 308 needs to go faster than like SD bullets to be equal.

A hardened target deflects forces from a soft bullet. This deflection can be overcome with "enough" velocity.

Making the assumption that penetration is proportional to stress (force divided by area of contact) and providing bullets are of more or less similar shape and construction, it turns out that penetration is proportional to the square of bullet velocity.

My experience with shooting steel is limited, but the armor plate I have doesn't even have a ding from 140BT's in a 7mmRM when shooting it at 150 yards. Knocks the paint off, but you can't feel any change in the smoothness of the surface. Lots of fun. I have not shot it with any X bullets yet and am curious to see how they treat the steel.

I do remember G&A having an article back in the 90's about the magic of 4,000fps. They showed a picture of a steel plate shot with a 25acp bullet fired from a 257wby; that thing cratered the steel when it hit at something like 4,300fps.

I'll preface this with a warning to all would be experimentors. When I was much younger, we decided to test steel penetration with a newly acquired 6.5x55 using 156gr. FMJ ball. We shot some hardened plate, (maybe grader blade?) at about 30'. The bullet or a fragment thereof, came back and hit my cohort, who was about 2' from my right, in the left elbow, ripping a fair chunk out of his heavy cotton duck parka. Stopped that nonsense right there!
Years later, we got hold of a flywheel from a skidder motor. IIRC, it was about 12"-14" dia. by 2" thick and quite heavy. We stood it on a stump about 50yds away and shot it with the following:
1. .220 Swift, 50gr. Speer with a hot load of 4064. The bullet penetrated 3/8"-1/2", but just tipped the flywheel over, almost gently.
2. .30-06, 173gr. Lake City Match with WW760, doing about 2850fps. This penetrated about 1/4" of the flywheel, but slapped it down with considerable authority.
3. .338 Win Mag, 275gr. Speer at about 2500fps. This penetrated only 1/8" or so, more like a dent, but it caused the flywheel to go spinning off the stump, landing 6'-8' away.
It seems to me that steel penetration has little to do with bullet performance on game, but as I'll freely admit, I'm still learning. We also shot some trees to test bullet penetration too.......

FWIW:

Brennecke hard cast 12 guage shotgun slugs penetrate through the fender of a 1968 Buick, through the power steering unit and well into the outler layer of the engine block at 12 feet.

This result was repeated and confirmed on a 53 ford pickup.

Don't ask. . . .

BMT

I remember reading about bullets punching through steel plate years ago, and it was the same thing, velocity counts. One thing the military has to consider that most hobbyists don't, is whats left of the bullet after it penetrates the armor. 4,000 fps varmint bullets may punch holes in armor, but they might not be good for much after they make it through.

If you want to see what AP bullets are really good for, try shooting sandstone blocks, but thats a different matter alltogether.

FWIW:

Winchester 12 gauge foster slugs will crack an engine block but just leave a lead smear on the surface. They also land with a thud somewhere behind you.

Tim

BMT...

I dunno much about hunting bullets versus steel, not sure there is much to know in any case. There's steel and then there's Steel. Not all created alike and I've yet to see a critter hide behind any of it. Armor plate is a different animal and stopping small arms AP has been commonplace for a long time. The ability to resist the penetration of metals or ceramic plate armor pretty much fades with the .50 BMG AP or larger rounds. Projectile construction is quite important. 5.56mm or 7.62mm caliber cannot be a serious contender for such purposes.

Those who don't think a 5.56 will swiss cheese- as in the vaunted complete pass through, a car or pick up are really deluded. the SS109 ammo penetrates as deep as M2 ball in -06 or standard 7.62 ball does at 100 yards, the 5.56 does lose depth faster than the .30's. Even 9mm will penetrate car doors, a .45ACP 2 of them for sure, the issue with windshields is the slant, the more slant the greater the effective thickness is.

My back stop is 2.0" boiler plate and even .50 BMG ball does NOT penetrate it, nor the brass 650 and 700 grainers. .270 WSM 140 TSX's and .257 Bob 100 TSX's actually leave deeper craters than military ball ammo does.

Having worked on a shooting range for a while and having some sample hardened plates myself, I have noticed a few things

Velocity seems to be the biggest single factor.
Bullet construction DOES has some effect not talking green tips here either]
The type of steel makes all the difference in the world. AR plate is a different animal than 1016 mild steel!!!

I had a 3/8" hardened plate that we were testing stuff on. My 7mm-08 would penetrate it as long as I was under 75 yds. I was using 110 TNTs [the only bullet I could get to penetrate it out of that rifle]

My 300 WBY would penetrate it at 350 yds with a 180 grain Fail safe. A 6.5x284 made a nice little hole at the same distance with a 129 Horny, but only a dent with a 140. Go figure??

17 Rem 25 gr HPs are "better" than 500 + gr cast bullets in 45-70!

I had a 12 inch disc of 1 inch mild steel, which we thought might be fun to shoot from 25 yds with the old 06. My 165 gr ballistic tips at 2800 fps MV were only leaving 3/16 inch craters on the surface.

I also had some military 30-06 AP rounds. The penetrator went to a depth of 7/8 inch and left a pimple on the back side of the one inch plate.

We got smart and found more enlightened pursuits when we realized the noises we were hearing behind us in the blackberry bushes and on the aluminum side of a trailer house was splash back.

I had a friend who set up a private range on his property.The range was 100 yds.Behind the targets were two large steel construction plates of the type used to cover excavation in roadways in order to allow traffic to pass over without refilling the excavations.The plates were leaning over the targets in a manner that would deflect all bullets down into the earth.
Literally dozens of different cartridges of all levels of power were fired into this set up over the years.The only time he would notice holes appearing in the steel was after firing fairly hot .243 loads.He and another friend and his wife were big .243 fans and experimented with a number of fairly hot loads over the years.These loads typically were above the maximum listed loads in the manuals and velocities were typically pretty high.These were not typically first shot penetrations but would appear after tight groups had been shot.
They did not observe the same phenomenon when firing various .25,.270 (including Weatherby) 7mm or .30 caliber cartridges,including various magnums.

Interesting thread, I've been practising alot at our range shooting the 200 metre chicken and our 300 metre pig off shooting sticks. I've been shooting my sons 30-06 loaded just under 2800 fps with 165 hornady's and my 300 win mag with 168 TSX at 3200. I was getting frustrated because I kept missing with my gun and hitting with the 06. So I decided to shoot the pig off the bench and I noticed it moving a bit so I walked down, it is riddled with copper stained holes and penetration marks fomr the 06 leadcore bullets.

So it would appear that both velocity and bullet construction matter vs steel plating.

I want to give a simplified explanation why velocity is so important.

Remember the joke, "it's not the fall that hurt, it was the sudden stop". Forces are applied at the point of sudden stop. It's the point that a bullets momentun converts to pure force. A deflected bullet doesn't stop (altogether) so it doesn't hit as hard. Velocity makes it harder for the target to deflect or slow down the bullet.

Theoretically, if a bullet was stopped instantaneously ... in 0 seconds, the force applied to the target is infinite. Look at the example of a yo-yo. I can work it up and down easily without breaking the string. I can also jerk it to a sudden reversal of direction (stop) and snap the string. The forces jump up proportionally.

When a bullet strikes steel, momentum (mass x velocity) is converted to force in pounds. As soon as the applied force reaches the threshold of the steel, the bullet is allowed to pass.

Because a solt steel will dimple sooner, the pocket has the effect of containing the bullet mass. It can't squirt out the sides like what happens on AR plate so it decelerates more - and more momemtum converts. You can say it actually hits harder. AR or the ceramic armor simply are able to deflect the direction of momentum. Steel also has toughness properties, mild steel is not tough, cannot absorb the energy as well.

I said simplified explanation, maybe not. A hard bullet hits steel harder (more force) than a soft one. Hunting bullets hit a soft steel target harder than hard steel. Any bullet hits harder if it's not splattered at right angles or deflected; hits harder as velocity increases and hits harder with higher sectional density.

As far as armor goes. You want hard to deflect or tough (kevlar) to slow the sudden stop. The best armor is a combination of the two.

My 30-378 Weatherby used to shoot through plate steel like a knife through hot butter.

$bob$

varmit bullets dont punch through steel plate as much as they melt their way through...........


question....how well do you guys think zinc plates will hold up to firing? ive got some of those around that are about perfet target sized.....not very thick though....maybe 1/8 inch maybe ill haul one out to the country this weekend for grins

lots of info here. Check out the 5.56 vs 7.62 section.
Ammo info

In passing through steel, bullets do indeed melt their way through. Ackley did a series of experiments, and some of his small caliber, very hot rounds penetrated quite well.

Given that, you can apply basic physics. You have to convert enough of the kinetic energy of the bullet into heat, in order to melt the hole. So bullet KE is very important. More KE provides more energy, and will melt more metal.

If the bullet is smaller, all other factors equal, then less metal has to be melted to make a hole.

The key is lots of KE in proportion to the diameter of hole you want to make.

I do agree with your statement, but I had this happen to me several years ago. A friend and I were shooting several different calibers at pepper poppers between 75-100 yards away. He shot several rounds of .308 and .223 at the poppers. We wedged the hings so the poppers would not fall. Both of the above rounds left small dents but we could not get them to penetrate the steel poppers. I then shot the same popper with a 45-70 using a 300JHP Remington bullet at 2,500fps. This round went right through the popper. I shot several rounds and each went through the popper. I also tried several hard cast bullets in .45-70 and I couldn't get any of them to pass through the steel popper. I'm not a physics major, but I decided that the 300grain bullet passed through because of velocity and weight, wich must have created a lot of heat upon impact.

Our Silhouette Range bans 22 Centerfires and Magnums. I've seen targets barely dented by a 7 mag but had holes in them from a 22-250. Anything with high enough velocity will get you to rewelding the holes in the targets. The big boomers won't knock holes in them like a 22 centerfire but they will bend them to where they won't stay on the target stands. Using either on the Silhouettes will get the match directors pretty testy.........................DJ

Had to prep a big pile of 14" x 14" baseplates, for a steel silo once. Plan was to bolt the imbeds to the plates, fit 'em into the Sonotubes, and than swim grout them for load bearing final spec. ( this is WAY easier that trying to get imbeds all square, and fit pre-prepped bases)

Bid against the local machine shop, and as I was already in as a welding and steelhangin' contractor, I got the job.

Smokin'....130Gr hunting bullets, .270 Win did the job hansomely, at probably too close a range.........but you talk about clean holes......opening then up with the "Blue Drill" ( oxy torch) afterwards was a cakewalk.....it's the pre-heat and initial piercing that's so time and fuel consuming......so actually made a buck,on that one, and had fun, so doin'.

so,........130grainers at smokin' 270 win. vel....woiks.

This was a common A-36 grade steel 1/2" plate, by the way....not armor.

GTC

A bullet does not need to melt through steel. Machine shops punch holes more efficiently. I'm not sure there is enough kinetic energy to convert to caloric heat via friction to melt a hole.

The observation of what looks like a burned hole is probably a heat burnished sheared edge. I have read however about anti-tank rounds that create so much heat that vaporized metal kills the tank occupants. Not sure, I'd like to see the math.

When I shot my 7mm-08 into the plate, I had it tied to a large pine tree. The rounds that went through were stopped by the bark and were easy to pick up off the ground beneath the plate. They were perfectly sheared plugs- that didn't fit the holes they came out of!!!

I forget the exact science of it but metal plates have plugs and basically when the bullet hits it the plug slips therefore actually not penetrating it, but causing the distinct hole. Esox357.

I remember reading that, but I think those rounds used depleted uranium, or something similar, for the cores.

Tim

Yeah, depleted uranium in a projectile with huge mass and ultra velocity going thru several inches of tough steel designed to resist penetration (shear).

I see heat as the waste product of a primary event or action - and when kinetic energy is converted there is always loss. It can't be converted completely to the heat form.

Sure, heat is present but I suspect it is a byproduct and not high enough to melt a caliber size hole. Remember, we're talking about bullet against relatively thin plate.

Say a bullet travels with 2000 ft-lbs kinetic. This can be converted to 100% caloric energy with a multiplier (too lazy to get my conversion table) I don't think it would be too hard to get an idea of how many calories it would take to melt a hole.

I'm thinking you find out first how much electrical energy it would take to melt a hole (virtually instantly) and convert that mathematically to ft-lbs. Intuitively my reaction is that rifle bullets don't have the energy equivalent. I could be wrong.

Heat was definitely a factor in the craters made in my one inch plate.

Does everyone remember the famous photo of the milk drop hitting the surface of a jug of milk. The stop motion photograph portrayed a perfect crown of droplets from the impact.

That is what the impact craters of my 165 BT's on one inch plate looked like. Little crowns of melted and resolidified steel.

The order of events when a bullet strikes metal is always swage, shear then heat. That�s the way a bullet attacks every time � and that is the ordered way the bullet responds to the collision - mushroom � break apart�..melt.

How far a bullet gets into that sequence depends on what both bullet and target are made of and how much energy is present. All of this is the reason for the different observations of the event. Every collision has its own unique dynamics and degrees of progress.

A bullet hits a metal plate. In the first nanosecond it�s swaging and being swaged � the bullet is just trying to push the metal out of its way. The waste of that dynamic is friction or heat. What you see is a dimple in the metal and if you run to the target you may feel warmth at the spot. The bullet had deflected or simply dropped to the ground exhausted.

If the metal can�t be pushed out of the way easily or fast enough and there is still kinetic energy left to dissipate, the impulse forces break the metal by pulling it apart and/or shearing it. Once again the byproduct (waste) is friction or heat.

If the metal can�t easily be swaged and sheared because it is too tough, thick or hard and there is still energy left to dissipate that can�t be deflected � you�ve dimpled and torn the steel but the bullet is still come�n cause you�ve loaded hot, plus the bullet is tough and hard itself. Then you finally get the meltdown but only because there was not other way for the energy to dissipate at such a high rate of exchange.

I tried to figure how much more energy it takes for a 308 to penetrate like a 22 all else being equal. But there are too many variables and conditions are never equal. Maybe 30% more energy � not velocity � energy.

Oh, I stayed at an engineering school once. IIRC there were some guys there that could melt steel with their minds.

Hey wait a minute, doesn't lead and copper melt before steel. And didn't we learn from Rosie that you can't melt steel.

What if the steel plate was moving at 2800 FPS and the bullet was stationary. I guess the steel melting theorists would opine that the kinetic energy of the steel would melt the bullet. I wonder if there would be a hole.

Dripping sarcasm, I note. How appropriate.

IF the bullet melted its way through the plate, it would start melting in the center of the hole where its meplat strikes first. The plugs that I picked up looked quite similar to those made by an ironworker when punching holes, albeit a little more mushroomed. Nope, It just has to overcome the strength of the steel, whether tensile/elastic or what have you.

If you happen to hit the same spot a few times in a reasonable space of time, you can work-harden the steel to the point where it will fail and allow and otherwise inadequate round to penetrate.

There was an article in PS one time where a guy used a hardened plate as a backer with great success until one day he happened to shoot a group that was virtually one hole- you guessed it, there was a perfect hole in the steel behind the target- my guess is the last bullet finally overcame the steel and punched right through.

Velocity indeed is important, but it is rather difficult to say it is the most important, since penetration is strongly dependant on the combination of factors (in ballistics), such as the material hardness, shape, heat-resistance, density and mass (besides velocity). For example, a pointed copper bullet will penetrate better than a pointed lead bullet, because of the copper's superior hardnesss & heat resistance compared to lead (assuming they both have the same mass & velocity). If they both have the same final output in energy (foot-pounds of force per E=(mV^2)/Constant), then one that will penetrate say a steel plate better will be the one with higher heat resistance, hardness and density. A good example, a good armor piercing round will have a tungsten-carbide core which is extremely hard and dense -- tungsten-carbide is rated 9.0 on the Moh's Hardness Scale, which is only exceeded by a diamond in terms of natural hardness. tungsten-carbide is also extremely heat resistant. It has the highest melting point among metals, which is why tungsten-core rounds are ideal for armor penetration.

A friend of mine has a couple of 3/4" (I think) plates on his range. Have made no conclusions, but i have noticed that TSXs leave a much deeper crater than any lead-core bullet I have tried.

John

This effect only occurs when the velocity of the projectile exceeds the speed of sound in both the projectile material and the target material, about 5000 fps with steel. The physics are then the same as liquid hitting liquid--at 5000 fps. The projectile does not go that fast, of course, but an internal "shaped charge" accelelerates a portion of the projectile to that speed upon impact. This effect has nothing to do with bullets penetrating steel.

True with a HEAT round, but not with a Sabot. The sabot rounds DO go approximately that fast, and will completely penetrate a T54/55 purely on kinetic energy alone. Seen it myself....

John

Hmmmmm. Let''s see. It is lethal enough for armed combat but not enough so for deer most of which are usually smaller than a man.

If it will kill a man humanely it will do the same for a deer at the same range.