On another forum that has nothing to do with reloading or guns for that matter, a poster told his story of shooting at one of those spinning steel reactive targets. It worked fine with 22 rimfire and even 9mm. But his 270Win put a hole clean through the target plate. He was surprised it happened and asked for comments. Here was one reply:

quote:

Its a really simple reason rifles do so bad on steel plate. Its the twist of the rifling and the velocity that does it. The bullet actually screws its energy through the plate. Same reason that makes bullet vests work. Spinning bullet hits vest and wraps many strands round itself and the vest catches the bullet...Ballistic data is my specialty.

I called BS. Am I right?

I too would call it BS! At one turn in say 10 in. a plate 1/2 in thick would only recieve 1/20h of a rev. I don't think that qualifies as screwing into a plate. I think that he's screwing with you!

He's half right. It's the velocity...

MKane160

quote:

Spinning bullet hits vest and wraps many strands round itself and the vest catches the bullet...Ballistic data is my specialty.

What a shitbird

quote:

Originally posted by onefunzr2:
...I called BS. Am I right?

quote:

The bullet actually screws its energy through the plate

I say shoot the "Ballsitic data" guy in the ass and see how "screwed" he gets

Sounds like a CSI wantabe

The "ex-spurt" (a drip under pressure?) is misled, but I wouldn't be too hasty to condemn him as a person.

With much of the trash which is published, posted on the internet, and shown on TV, there is so little technical knowledge and so much "sounds reasonable so it must be right" error-laden opinion relayed to those who actually want to learn, I am not surprised at his statement.

I have personally seen a special on ballistic vests on TV that came very close to saying what he did about them. It is still wrong, but who can blame a relative newby for believing?

It is always better for our sport to educate than to condemn.

I give the guy credit for both having tried to learn, and for trying to pass on what he thought was knowledge, even if it wasn't correct.

And I give you credit for telling him it was incorrect and providing a correct explanation.

Generally speaking it is the kenetic energy at the point of impact that puts a hole in a steel plate.

There have been a lot of .223 holes put in "pepper popper" targets meant for pistol and shotgun use.

I think there is some validity to the notion of "rotational velocity." If you shoot a high velocity bullet out of a 9" twist barrel you may be sending it down range at 250,000 rpm - that has to mean something.

quote:

I think there is some validity to the notion of "rotational velocity." If you shoot a high velocity bullet out of a 9" twist barrel you may be sending it down range at 250,000 rpm - that has to mean something.

It means it is turning once every 9" nothing more. Try a same wgt 223cal bullet at the same velocity in 1/7" and 1/12" barrels on ballistic gel and see if there is a difference in penitration.

quote:

The bullet actually screws its energy through the plate.

I'm no scientist, but I'll venture a comment - it's probably a combination of factors, not the least being velocity. I suspect that heat generated is not entirely innocent, either

Yes, you were right to call BS.

that belongs in the humor forum

quote:

Originally posted by Alberta Canuck:
And I give you credit for telling him it was incorrect and providing a correct explanation.

Don't be too hasty there, AC. I just raised the flag on the part where the bullet with threads screws itself through the steel plate or wraps onto the fabric. But I didn't have any data at hand to prove my contention, so I left it at that. Semi-wild-assed guesses are not my forte. I'd like to give empirical evidence if possible. His claims were so outlandish, none of my reference books covers such a thing. That's why I decided to ask here.

quote:

Spinning bullet hits vest and wraps many strands round itself and the vest catches the bullet...Ballistic data is my specialty.

Total BS from a mind that tends to wrap itself into tight knots from which it cannot escape!

I have blown quarter inch holes in half inch steel plate with a 22-250 many times. Bullet did it with impact alone, the entry crater shows that clearly. Certainly not by "screwing" itself through.

Going some 3500 fps at the muzzle, my bullets were maybe 3000 fps at the target. Meaning, it only took .3 thousants of a second to travel a foot. We may divide that by 24 and get the approximate time it took to pass through the 1/2" plate, and it only completed about 1/24th of a turn doing it. Not much time or chance for screwing around in that, is there?

You did right to question that "ballistics specialist."

Oh, I dunno, in my experience screwing does create a lot of energy, some of it additive.....

The screwing therory is a dud --PERIOD! About 20 years ago one of the guys at work made a statement about hiding behind a car door for protection. I stated it was better than standing in the open but if the gun being fired at you was a magnum hand gun or a large game capable rifle you were going to get a hole in you to. There was lots of unbelieving discusion aimed at me so I took home 1/4 - 3/8 and one inch mild steel plate. (I'm a welder) I fired 357 ,44 mag, 223 and 30-06 at the plates. I can't remember the exact details of what went how far but can say that --velocity--gross energy and bullet construction were the big factors in penetration. The 1/4" was prety much cheese for all rifle bullets. 223 fmj would almost squirt the 3/8" but light jacket varmit 223 would only do a dent. One inch would bulge the back side with FMJ 30-06 and Corelokts would do a healthy divot. 223 FMJ ony small divot. Divots resemble moon crater with displaced steel sticking up outside the crater. I hauled the plates back into work and realy put the fear of KABOOM in some of the unknowing people.
There is a difference of damage also between rigidly supported steel and spinners. The high velocity will have a penetration edge on spinners versus say a 45-70 500 grain. Even though the 45-70 bulldozer had the energy the time it had to apply that energy would impart movement in the target versus the light speed FMJ of 223 will do a better divot or squirt completly thru. I got my first education on this when I was 13. My Uncle who was also a welder had a 375 H&H that had legendary powers--if he could actualy hit with it! He bragged that it would crack out the back side of one inch plate. He brought home a chunk from work to prove its magic and the families were assembled to watch the show. I had fathers 30-06 and military surplus FMJ which we could get for a dime per round. Uncle let fly a blast and every one marveled at the damage the monster slayer imparted on steel then it was my turn. The FMJ bulged but did not crack out the backside of the plate. Uncles fire was some what diminished of his monster killers ablilities compared to my Fathers POP gun!

The "expert" got it all wrong. He's not a ballistics expert, he's a B.S.expert.
Bear in Fairbanks

I tried screwing my way thru college...almost made it too. Couldn't keep my velocity up.

On another note I am amazed at what even varmint type bullets can do to 1/2" steel plates. Some place on the net there is a slow mo video of the "pass thru", very cool.

There is no doubt that the primary influence on bullet penetration is probably the strength/integrity of the bullet (so it stays together long enough to penetrate...and which is why highly frangible bullets DON'T penetrate even at high velocity). Second, and almost as important, is velocity. Third I suspect is the angle at which the target is struck. Fourth but much less important to my thinking, is likely projectile shape.

Anyway, just as a matter of interest, when the .250-3000 Savage was first brought out, almost everyone confused penetration with power. So, to hype the "power" of the cartridge for hunting, sales reps used to set up demos where they would drive an axe into a chopping block. Then they would shoot at the head of the axe with the .250-3000 and an 87 gr. bullet. The bullet would fully penetrate the steel axe head on both sides of the "eye".

Hunters and prospective purchasers were duly impressed, and many then even took their new Savages to do things like shoot African lions, Alaskan brown bears, etc. Some soon learned the practical difference between velocity effects and sheer power.

onefunzr2,
You are absolutely correct. The bullet will be spinning no faster than the rate of twist in the barrel and in fact will be slowing down from the point where it leaves the muzzle.

A slug from a .270Win rifle has many times the energy from a .22lr or a 9mm parabellum. A .22lr runs 1100-1300fps and the 9mm has a muzzle velocity of 950-1150fps. Contrast that with the muzzle velocity of a 270Win that runs around 2800fps with a 140gr. bullet. At 2-3X the velocity of the other rounds, a swinging target simply does not have time to get out of the way of the .270 slug.

Go ahead and throw the flag!

it is the amount of energy being concentrated in a small area that causes the steel penetration
i have shot plates with military fmj stuff and then made holes through it with the 220 swift. and regular soft points.
whats up with that?
same thing with making a hole with a torch, you can concentrate the heat and cut steel but a weed burner ain't gonna do it.

ONEFUNZR2

You shoulda made the letters bigger and maybe used bright red flashing neon!

Other than that, I in my limited knowledge concur with your opinion.

TCLouis, do you think this conveyed my sense of BS?

Well, you gotta give the guy credit for imagination.

One thing I would point out to those who claim the rate of twist makes the bullet turn ("screw") too slowly to even make a full rotation in bulletproof vest material, remember, once the bullet hits the best its forward speed slows considerably immediately, but the rotational speed slows only slightly at first, enabling some of that "wrapping" and entangling. I imagine that people who have actually examined used vests have observed this and concluded this contributes to the vests' protection.

Remember, a kevlar best will stop a bullet, but not a knife.

Many thanks to Alberta Canuck for the kindness shown:

quote:

Originally posted by Alberta Canuck:
The "ex-spurt" (a drip under pressure?) is misled, but I wouldn't be too hasty to condemn him as a person.

With much of the trash which is published, posted on the internet, and shown on TV, there is so little technical knowledge and so much "sounds reasonable so it must be right" error-laden opinion relayed to those who actually want to learn, I am not surprised at his statement.

I have personally seen a special on ballistic vests on TV that came very close to saying what he did about them. It is still wrong, but who can blame a relative newby for believing?

It is always better for our sport to educate than to condemn.

I give the guy credit for both having tried to learn, and for trying to pass on what he thought was knowledge, even if it wasn't correct.

And I give you credit for telling him it was incorrect and providing a correct explanation.

Want to prove what is B.S. and what is not? Devise a real-world experiment to test the theory.

Hypothesis: The rotation of the bullet is what allows a 270 to penetrate a mild steel plate.

Test: remove the rotation from the bullet, but leave the velocity.

Method: Bore out a barrel in 270 size without rifling, or with minimal rifling (just enough to keep the bullet stabilized in flight to the distance of the target). Shoot the target(s) and examine the holes. Film in high-speed if possible.

You might get a rifle with a badly shot-out barrel and use it for a few shots. If you could machine out the rifling completely or have a gunsmith cut straight rifling into a barrel, so much the better. There muse be old, replaced barrels out there somewhere that could be gotten cheap or free.

Write up your results for any scientific journal you can get to accept your submission.

My unsupported opinion is that rotational velocity contributes nothing to penetration on a steel plate (some basis is seen in high-speed photos of bullets penetrating steel). My unsupported opinion on the relationship of bullet rotation to penetration of a kevlar vest is still up in the air, but based on what I have heard, I think EXTRACTION of the bullet from the vest may be made more difficult because of the rotation.

To the guy who supplied the alleged answer, "The bullet actually screws its energy through the plate. Same reason that makes bullet vests work. Spinning bullet hits vest and wraps many strands round itself and the vest catches the bullet...Ballistic data is my specialty.", I have this observation.

Ballistic data is your specialty? OK, you may specialize in it, but are you any good at it? I don't mean to be insulting (well, maybe a little) but when you produce a startling piece of information, it is good to cite empirical support as well as the theoretical explanation.

Nothing said here so far is so cut-and-dried that it defies refutation. (In my opinion)

Lost Sheep

Remember, only believe half of what you see and one quarter of what you hear. That goes double for what you get from the internet.

Also remember, even the idiotic stuff might have a kernel of truth buried in there somewhere.

The biggest difference between the 9mm and the 270 is the energy absorbed by the target. (this is why you use the pistol to fight your way to a rifle)

Typical 9mm with 124g bullet at 1200 ft/sec will yield about 396 Ft/Lbs.

Now consider a 150g slug from the .270 at 2850 ft/sec which gives about 2705 ft/lbs of energy concentrated on an area 40% smaller


Still, spinning bullet behavior is interesting to think aobut. Consider, if you fired a bullet straight up it would leave the muzzle at say 3000 ft/sec and spinning at about 250000 RPM. As it goes higher the velocity drops lower until it is zero for a split second, which means it is sitting there motionless for a split second, but still spinning at 250k RPM.

quote:

Originally posted by A/C guy:
The biggest difference between the 9mm and the 270 is the energy absorbed by the target. (this is why you use the pistol to fight your way to a rifle)

Typical 9mm with 124g bullet at 1200 ft/sec will yield about 396 Ft/Lbs.

Now consider a 150g slug from the .270 at 2850 ft/sec which gives about 2705 ft/lbs of energy concentrated on an area 40% smaller


Still, spinning bullet behavior is interesting to think aobut. Consider, if you fired a bullet straight up it would leave the muzzle at say 3000 ft/sec and spinning at about 250000 RPM. As it goes higher the velocity drops lower until it is zero for a split second, which means it is sitting there motionless for a split second, but still spinning at 250k RPM.

Interesting fact:

Remember the the Watts suburb of Los Angeles in August of 1965? There were hundreds of shots fired up in the air. For several years afterwards, roofers would occasionally find bullets embedded in roofs. Most of them were buried shallow, but nose-up. I surmise that this means they were probably still spinning and gyroscopically stable both on the ascend and on the descent.

(Source of the base-down, nose up roofer testimony: a letter to a gun magazine in the late 60s. Don't remember which one)

Lost Sheep

quote:

Originally posted by A/C guy:
The biggest difference between the 9mm and the 270 is the energy absorbed by the target. (this is why you use the pistol to fight your way to a rifle)

Typical 9mm with 124g bullet at 1200 ft/sec will yield about 396 Ft/Lbs.

Now consider a 150g slug from the .270 at 2850 ft/sec which gives about 2705 ft/lbs of energy concentrated on an area 40% smaller


Still, spinning bullet behavior is interesting to think aobut. Consider, if you fired a bullet straight up it would leave the muzzle at say 3000 ft/sec and spinning at about 250000 RPM. As it goes higher the velocity drops lower until it is zero for a split second, which means it is sitting there motionless for a split second, but still spinning at 250k RPM.

Two hundred fifty thousand RPM? Seemed awfully fast. I did the math. A bullet travelling 3125 fps out of a barrel with a 9 inch twist would indeed spin at 250,000 rpm. But air friction would slow that down some in the 25 seconds or so that it would take to reach maximum altitude of 10,000 feet. Calculations were done ignoring air friction on the bullet, so maybe seven or eight thousand feet might be more realistic, but the bullet would still be spinning probably in the 200,000 rpm range (just a WAG). You guys with ballistic computer programs could run better numbers, at least on the flight path.

So, does that mean if I were in a hot air balloon about 8,000 to 10,000 feet and someone fired a bullet at 800 fps, I might be able to reach out and catch it with my hand when it reached the top of its trajectory? But then the spinning would still have a chance to hurt me with a friction burn to my palm?


Cool, I will use a tin cup instead of my hand.

Just let me get my lawn chair, fill up 40 or 50 helium balloons and get someone to shoot at me with a .45 ACP. Volunteers? I can see the headlines now.

Any suggestions as to what the headline should be? "Lawn-chair balloonist takes bullet in ***, spins out of control."

Lost Sheep

quote:

There were hundreds of shots fired up in the air. For several years afterwards, roofers would occasionally find bullets embedded in roofs. Most of them were buried shallow, but nose-up. I surmise that this means they were probably still spinning and gyroscopically stable both on the ascend and on the descent.

Myth Busters did a thing on firing bullets straight up. Pistol bullets - the only ones they could find on the ground - fell randomly. The rifle bullets must have been blown a long way down wind. I always suspected they would come down base first. Now I know.

By the way, just try to picture 200,000 rpm! It's more than a hundred!

I would suggest it very likely that the spinning bullet being caught in the Kevlar vest theory has some merit. It could well be a factor in bullet capture. When I recover bullets from my firing tube, they are sometimes tightly twisted into the rags that caught them. They do often have strands caught in the noses from preceding rags that probably increase the frontal area and assist in the capture. But they were undoubtedly still spinning when they stopped! But this does not always happen in the trapping medium. Sometimes they pass right through into the sand trap. Sometimes they deposit bits of material in subsequent layers.

The middle bullet was stopped in the rags. (It was sitting there nose forward!) It still has some rag stuck in the hollow point. The top and bottom bullets made it to the sand. The top one hit the sloping side of the sand pot.

quote:

Want to prove what is B.S. and what is not? Devise a real-world experiment to test the theory.

Hypothesis: The rotation of the bullet is what allows a 270 to penetrate a mild steel plate.

Test: remove the rotation from the bullet, but leave the velocity.

This would be easy. Fire a cast lead bullet without a gas check at a steel plate from close up. Do protect your legs from molten steel ejecta or at least have a first aid kit nearby. Do wear eye protection. Fire several shots. The bullets will strip through the rifling so many of them will hit sideways. Those don't penetrate that well and the lube groove pattern gets left on the steel plate.

(Yes I have done it and no I did not get hit in the legs - I was expecting that and took precautions and yes I have been crazy all my life!)

P.S. Those bullets in the pic are the tapered 'grooveless' ones I've been developing for my 303 Brit - 243grs worth!

This is how I lube them.

There's no way a bullet is spinning one turn in nine inches after it comes out of a gun barrel. Think about a football, it is spinning that fast when you throw it. Just because the twist is "one in nine" doesn't mean that is what it will continue to spin at once it leaves the barrel. A bullet is in effect a gyroscope. This is what keeps it on its course to its final destination.

If you fired the gun straight up in the air, it would still be spinning very fast when it reached the apex, when all upward or forward motion had stopped. As it falls to the ground it is still spinning, not nearly as fast though.

A 180 grain bullet traveling at 2700 feet per second is completing 3240 revolutions per SECOND. X 60 seconds that is a whopping 194,400 revolutions per MINUTE.

The sheer velocity X the weight of the bullet is what pushes it through the steel. I have shot 1/2" I beam steel with a 223 at 100 yards and it goes right through with PSP factory ammo.

A kevlar vest will not stop a rifle bullet. It might slow it down or stop it when the vest (and the person in it) is 200 or 300 yards away, but at 100 yards or less I doubt a vest would stop most rifle bullets used in a centerfire hunting rifle.

Ever shoot a empty pop can with a high powderd rifle ? The bullet often goes strait through the can with out knocking it over.
It even happens with a 22 using the super light weight pop cans common today.
A tin can from say some green beans is harder and the can will be more likly to move.
So, the bullet from this guy's .270 was moving so fast that its powder made quick work of the light weight material of the target spinner.
tj3006

quote:

The bullet often goes strait through the can with out knocking it over.

A fellow once set up a steel block, 16mm thick, 50 by 75, (5/8x2x3) on a pole at 100m and shot it with his 300 Win Mag. The block twitched a little and wobbled but did not fall over. The hole was close to a top corner. (The block was standing on its narrow edge).

Bullets fired in "direct fire" (near horizontal trajectory) lose essentially none of their spin during flight.

Yes air resistance slows them down in terms of forward velocity but doesn't act on the spin in any materially way.

Bullets launched near vertical experience the same forces and lose very little of their spin even in their much longer time of flight.

Bullets fired slightly less near horizontally at longer range targets are subject to somewhat different effects...
Fired at say 1000yd targets you find match shooters using slightly slower twist rates that will still stabalize the bullet but allow aerodynamic forces to overcome slight yaw rates.

theoretically speaking a bullet fired near vertically will return to earth point-up with >98% of it's spin but only falling at about 300-350fps, thus the shallow penetration observed.

where things get really weird is when bullets (or artillery projectiles) are fired at 35-55degree up angles
Unless the shell is specifically designed with aerodynamic
vanes (invented by Gerald Bull) to aid "spin recovery"
the shells will almost invariably return to earth tumbling wildly.

It is this tendency that makes possible the design of the "spin decay fuze" used in anti-aircraft projectiles
so that when the shell begins to wobble in flight near the "tip over" point of it's trajectory the shell self-destucts

a bullet fired from a modern rifle at a 40degree up angle is nearly as likely to turn around and fly back into the barrel that launched it than it is to return to earth point first

Now to the direct question, it's a matter of kinetic energy.

bullets NEVER simply penetrate homgeneous steel plates
The bullet striking and deforming generates heat as the metal is distorted, this heat can EASILY reach the combustion temperature of the steel and the bullet BURNS through the plate...

If you want proof of this simply shoot at a 1/2" thick steel plate with a 30-06 at 75 yards in the fading twilight.

you see the yellow/white flash of impact and you can see the heat disappate out into the plate.
Typically you'll lose sight of the "glow" as dull red as a circle
slightly larger than a silver dollar.

You'll also note that the hole made by a 30cal round is typically more like 1/2" in diameter.

what is really revealing is whet happens when a bullet ALMOST penetrate a 1/2" steel plate...

Say 55gr Ball ammo from a 223 at 50-60yards.
the result looks like someone stuck their pinkie into soft clay.

Long ago someone left a steel sillouette at the local public range I was disappointed when instead of knocking it over I simply perforated it with several shots.

the light show of the penetrations in the failing light was well worth the cost of the wasted ammo...

BTW, one of the many criteria in choosing steel alloys for armor plates was it's combustion temperature, because a softer plate with a higher combustion temp would often defeat penetrators that the harder plate with a lower ignition temperature would not.

Not to mention that most of the dammage to things hiding behind armor plate is usually caused by spalled armor fragments rather than by the penetrator itself.
Harder armors are more prone to spalling.

AD

I did not read EVERY posting on this thread. I only want to add that at one range where I shoot they have steel plates set up on a sort of rubber hinge arrangement at 200 yards. This is on the centerfire rifle range.

Depending upon the steel used, some of the plates that were tried ended up looking like swiss cheese and some did not.

quote:

Ballistic data is my specialty.

I think that said it all.

One of my brothers, a hunter but not a gun nut sighted in his .338 Win mag for the first time at a ranch that had a plate gong at 100 yards.

After getting a good sight in he was really disappointed that he missed the gong when he shot at it. So he shot at it 2 more times without any results. Then the walked down to get his target and found 3 holes shot through the 3/8" plate with the 250 grain Nosler Partitions.

Somewhere on the net is a video of a bullet penetrating a steel plate. There is going to be a 'plug' punched out and plenty of molten metal fragments ejected rearward as well as forward. In some of my tests, the bullet remained trapped inside the crater. (Can't find the pic).

This is a 4140 disc shot with a hornet. The punched out plugs are shown.



The problem with igniting steel is that it must first be evaporated then mixed with oxygen in sufficient concentrations to burn. Every time I burn steel using a cutting torch, I see the oxides formed. When I shoot a steel plate I only see steel fragments and if I can find it, the plug. A lead bullet punching a hole in steel, releases a lot of lead vapour and even more atomised lead which would expel any air present. I'm not too sure whether steel ignition takes place. It could do but I just haven't seen the evidence of it. Is there a source I can view?

Thinking about the bullet getting trapped in body armour by spinning - the bullet would have to have come to a near halt before any such entanglement could occur! My test bullets did not stop in the thickness of body armour - they travelled 300mm or so before becoming entangled. Before that, they punched holes in the rags! So, I am joining the BS flag brigade on that one.

Would a Ballistic Data Specialist be a Data Capture Clerk?