7mm vs Car engine

A guy at work has used 7.62 ball (regular old AP) to punch through 3/8" steel plate.

I'd think 7mm would work if you used FMJ bullets. He used an FAL for his 7.62X51 'tests'.

Edit: Sorry - AP meaning anti-personnel. He wasn't using black-tip armor piercing bullets. Regular old FMJs.

I have busted old six-cylinder cast iron engine block water jackets with a .357 Magnum hangun at over 100 yards.

All you have to do is get through one of the thin cooling system webs in the block and the engine is a gonner.

If shooting through a car body to reach the engine, there are a lot of things in the way anymore from the side. Still, with a front drive car, a 7mm mag through the radiator area would very likely make it to the block and bust something vital.

rc

I interpret this somewhat like the attacking grizzly. The question being not whether the bear/car will die, but will it die fast enough to keep it from getting you first.

Depends on many many many factors:

1. Most importantly, bullet construction. Steel/AP, FMJ lead, or a hunting bullet?
2. Is there anything blocking or protecting the engine? I.e. are you shooting an engine only removed from a vehicle, or through the side of the car and other stuff surrounding the engine?
3. Second most important, WHICH engine? Is it aluminum block or steel? What size, what style, what vehicle, how robust, etc.?
4. What ANGLE are you shooting from? Can make a huge difference.
5. Are you talking about piercing a cylinder wall, or just a thinner piece of steel encompassing the cooling channels?

So, there is no answer to the question, other than "sometimes yes, sometimes no", and "with steel/AP ammo, most likely, yes, and with other rounds, most likely, no."

The limiting factor with the 7mm would be the availability of suitable bullets. Most 7mm bullets on the market are OTM or JSP hunting bullets. Neither is ideal for penetrating steel.

I know I've put dozens, if not hundreds, of rounds through my 7mm onto a hanging steel tie plate at 100 to 200 yards. A 160 gr Nosler at 2970 fps impacts with a nice "CLANK" that leaves the plate swaying with a nice big pot mark, but I've never had a round penetrate the plate. I imagine if you could find a FMJBT in the 150 to 160 gr weight range and start it at 3000+ fps, it could do a number on a car engine. But if I have to choose between a scoped bolt action rifle for the task, or a semi-auto 7.62, I am going with the semi-auto. And if I am using a bolt action, it is going to be a .338 LM, minimum.

So short answer is that if you could find appropriate ammunition, it would probably work, but there are better options out there.

The best option for killing a block are 12 gauge slugs, of course. But a 7mm Rem. Mag will definitely do the trick. Most high-powered rifles will break an engine block without a problem.

Practical Testing

Tell him to bring his car over on Saturday and let's find out

Is it a John Deer engine? Get it?????

I think it's a matter of hitting the engine properly.. one shot to a cooling jacket won't stop an engine...
You'd have to wait for the engine for the engine to overheat, and in order for that to happen, there would have to be a serious shortage of coolant, and a 7mm hole isn't going to drain coolant all that fast.

I think that if you punched a hole in a cylinder wall, you COULD cause the engine to seize, but it would depend where you hit it. If the piston isn't traveling past the deformity, it wouldn't make a difference.
It's more of a question of shot placement. A carb, or distributor shot would stop an engine cold.

I believe your real debate is about whether or not a 7mm can penetrate an engine block, and I am inclined to say yes.
The real question is not whether a 7mm can stop a car, but whether or not you can hit a accelerating (think physics: speeding up, slowing down, or turning) target that is covered by sheet metal.

For car incapacitation, I would want a bigger round than 7mm.. the bullets are lighter than something I would want to use.
I would trust a .30-06 though, no problem.

OK... hold up a sec... engine blocks are generally not made of steel. They are either made of cast iron, or aluminum. In either case, I think a direct hit from a high velocity bullet is likely to break through a water jacket... Why?? Cast iron will break before it bends very far. And it tends to be more brittle than maleable... Aluminum??? pfff... that should be no real challenge for any decent centerfire cartridge 25 calibre and up...

Think of a hammer hitting a 1/8" thick piece of cast iron... it will break...

I agree with Schleprok... but like I said before. hitting a water jacket won't IMMEDIATELY stop an engine.

engine blocks are generally not made of steel.

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Generally? I have never seen or heard of one, although someone probably knows of some off-the-wall engine that is. Steel is not suitable for an engine block (or machinist tools, etc...) because it is far too malleable. Cast iron (AKA: grey iron - class 20, not to be construed with ductile iron or wrought iron), has great stiffness and a very low modulus of elasticity (about 10,000,000 psi vs. 30,000,000 psi for steel) and a modulus of rupture abut half of that of steel. Aluminum on the other hand has a modulus of elasticity about equal to cast iron but is very ductile. Translation: If it is a cast iron block the projectile will likely shatter the surface it impacts. If aluminum it will push right through and continue for quite a while (depending upon material thickness, bullet energy, and bullet composition).

Only engine block I have heard of that might be made of steel is a Crosley. My Dad drove one after WWII, and he told me the block was built of sheet metal. He could lift it from the engine bay by himself.

It had an overhead cam driven by a shaft with bevel gears. I think some Ducati drove cams the same way.

I did a search and they called the block: copper brazed sheet steel. They developed coolant leaks due to electrolysis. Here is a link to some pics of Crosley cars:

http://oldcarandtruckpictures.com/Crosley/

Another link with a better picture of the engine which is called COBRA:
http://jalopnik.com/381898/fighting-fascism-with-a-sheet+metal-block-crosley-cobra

You don't have to break the block to stop an engine. Strike the fuel pump(either lift or injection),the distributor, throttle body,etc and that puppy stops immediately.

Generally? I have never seen or heard of one

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Mav..223:
I was trying to be subtle... and your scientific/metalurgical description was excellent...

A co worker of mine honestly believes that a shot from a 7mm RM wont incapacitate an car engine. I believe otherwise

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Frankly, I don't see the point to such debates. Neither one of you is likely to need the correct answer, whatever it may be (see below). Just agree with him and move on, while harbouring private reservations if you so desire.

there is no answer to the question, other than "sometimes yes, sometimes no", and "with steel/AP ammo, most likely, yes, and with other rounds, most likely, no."

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I agree. There are too many factors to allow a definitive, 'one-size-fits-all' answer.

If you want to guarantee results, use a .50 BMG, or better yet an RPG.

Frankly, I don't see the point to such debates. Neither one of you is likely to need the correct answer, whatever it may be (see below). Just agree with him and move on, while harbouring private reservations if you so desire.

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Well, if all we talked about was always 100% realistic and morally correct all of the time, life would be boring.

But jimmyraythomason has a good point. If you hit a critical part of the engine, which is pretty much anything inside the engine bay, it will stop working. I think the real question is whether or not the 7mm will puncture the engine block though.

If my job was to stop moving vehicles with a firearm, you can sure bet I would take a Browning .50BMG or a Mk19.

Mav..223:
I was trying to be subtle... and your scientific/metalurgical description was excellent...

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Thanks...and as I figured I stand corrected (a sheet metal engine )

But jimmyraythomason has a good point. If you hit a critical part of the engine, which is pretty much anything inside the engine bay, it will stop working. I think the real question is whether or not the 7mm will puncture the engine block though.

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That's nearly exactly what I said.

It's more of a question of shot placement. A carb, or distributor shot would stop an engine cold.

I believe your real debate is about whether or not a 7mm can penetrate an engine block, and I am inclined to say yes.

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A .50 would not be my choice weapon to kill a car.

To stop an engine, you would only need to either destroy the spark, fuel, compression, or timing. I think it would be easier to load up some buckshot, and hope you hit the distributor, the carburetor, or alternator and battery, fuel lines, wiring...

Or better yet. Pop the driver in the face and don't worry about the car.

Shooting the driver will cause the car to veer off course, possibly into a tree.
Ah.....well........ I'm almost positive shooting an engine will ruin something, seen it first hand.
Customer #1 owed customer #2 around 5k ( I heard the yelling) customer#2 proceeds to draw his 357 and pop a few rounds into customer#1's 1988 379 Pete with a cummins "N" series just freshly in-framed and waiting for oil psi to start initial run-in.
It DID shoot thru ( well - into) the block - a 0.355"(+) hole in a 855 cubic inch engine causes lots of problems. Coolant doesn't necessarily drain out - it happens to be under 30psi or so. Oil is a little bit more pressurized, 45 - 55. The oil cooler on these model cummins is pretty thin aluminum. Doesn't faze a .357 hp.
Low water shutdown in about less time than it took for my mouth to close.
Personally I think the battery would instantly cause troubles, or any part of the ignition system.
But, a bullet from a pistol put a hole in a block, I feel pretty positive a rifle round would do more.

Shooting the driver will cause the car to veer off course, possibly into a tree.

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As seen in Dirty Harry, and again in Magnum Force!