Steel Plates and Copper Bullets

[atlas3025]

Went shooting a couple weeks back, and took along an AR500 plate that I shoot at 100 yards with 308 and 223. I have a buddy with a 300 Win Mag who shot it also with SMK's. The plate is holding up well enough. I have hit it hundreds of times with 223 and 308 FMJ's and HP's, with only a few very light craters. The 300WM SMK's didn't do it any harm.

Well, my buddy then shot at it using a Winchester E-Tip in his 300WM, and blew a hole straight through it.

As I understand it, the ETips are solid copper bullets. Maybe this is common sense, but I figured copper would still shatter and not pierce it since copper is softer than steel. Am I missing something about these bullets? Is there a penetrator in there?

Thoughts?

[Jonnin]

it does not have to be harder than steel to blow a hole in it. Clearly ---- lead cuts clean thru steel if the steel is thin enough. Copper is hard enough as well: you need a thicker plate when using a harder ammo. Also, not sure about the load data, but the copper may be moving much faster with a lighter slug (???) so that has an effect as well.

Basically, there is a lot more to the physics than just the relative hardness of the materials. If hardness were all that matters, lead would not be used, it is softer than most targets (including wood).

I am not conviced that copper would shatter. It is harder than lead, but not brittle at all. I have no idea, but it could just as easily not shatter (?). I would have to do more work to figure this out than I feel like right this moment. I may look into it later.

Edited October 2, 2012 by Jonnin

[atlas3025]

Yeah, I realize that it doesn't have to be harder to penetrate. I guess what I should have said is that I was not aware that solid copper bullets are armor piercing. I don't know what else you'd call it. It cut through 3/8 of an inch of AR500 like it was cheese. Those etips supposedly expand well in game too. I don't see how you do both of those things with the same bullet.

[gjohnsoniv]

Maybe the bullet weight along with the speed and material? I know really light and fast .223 will go clean through the ar500 plates without problem.

[Rightwinger]

Just a factor of speed and weight vs thickness and tensile strength. Depleted uranium isn't really hard just really dense and heavy. Put a layer of tungsten around it and launch it really fast from an Abrams main gun, and it goes through any armor currently known. What your friend did was launch a bullet that was fast and dense/heavy enough to penetrate.

I'll relate a story from the guy that makes the 458 Socom. He had a fellow in the shop that was fireforming brass, put some powder in new brass, pour some oatmeal or cream of wheat on top of that and seal with paper towel. Supposed to be enough to exand the brass in a chamber for a good overall seal. Well this fellow was working with some 50 BMG brass and poured a bit to much powder in the case. Tamped it down and sealed it with three wads of paper towel. Fired it at the wall and put three holes in the standard aluminum siding of the building. Paper through aluminum...just got to launch it fast enough.

[atlas3025]

That is pretty awesome Rightwinger.

I mean it all makes since, but those etips aren't THAT fast. I think it was a 180 grain bullet. So it would have been in the neighborhood of 3k fps I think. Its just funny that the lighter, faster, SMK 165 doesn't do much more than make a small dent. The etips are HP's too, I think. I know they have a polymer tip.

[Rightwinger]

The polymer tip may also be the deciding factor. If it's right on the edge of penetration or deflection, the polymer may be acting as a starting point then a lubricant to hole the plate.

[dlm37015]

hornady gmx bullets do yhe same thing

[jtmaze]

Look at the actual kinetic energy of the bullets. That is where it is at.

JTM

Sent from my iPhone

[StPatrick]

Look at the actual kinetic energy of the bullets. That is where it is at.

JTM

Sent from my iPhone

Exactly so. Any object can pass through another if carrying enough energy. Remember the scene in Kill Bill II where the guy punches through 4" thick boards? He could in real life if human hands moved fast enough, as opposed to in a movie (though the hand would be liquified in the process, so it's a one-time proposition). It's not mind over matter - speed kills. It's one of the reasons ultra-high speed space travel (e.g. approaching the speed of light) isn't thought to be possible. At those speeds, even the occasional hydrogen atom found in space will tear through any material known often enough to leave the crew flying the doomed ship an irradiated mass of Jell-O.

[RED333]

300WM, some loads go over 3000 FPS, at that speed you can put a stick into steel.

And engery getting close to 4000 ft·lbf.,

my .308 with FMJ surplus is going part way(close to 1/2 way) into a 3/4 steel griddle plate.

[atlas3025]

300WM, some loads go over 3000 FPS, at that speed you can put a stick into steel.

And engery getting close to 4000 ft·lbf.,

my .308 with FMJ surplus is going part way(close to 1/2 way) into a 3/4 steel griddle plate.

I get that too...but the 155 grain SMK's going faster from the same gun splattered and didn't hurt the steel. I know copper is harder than lead...but I didn't think it was THAT much harder.

[peejman]

Got pics of the holes? Good close-ups. I'm curious.

[Jonnin]

I get that too...but the 155 grain SMK's going faster from the same gun splattered and didn't hurt the steel. I know copper is harder than lead...but I didn't think it was THAT much harder.

This is a multivariable equation that is very difficult to eyeball. You have the energy (effectively, damage done on impact), momentum (effectively, the difficulty in making it change directions, or bounce off), the relative hardness, thickness of the target, the bullet material's tendency to break/splat/frag vs staying together, and more. All these and more have to be examined to understand the big picture. I kid you not it would take me a solid month to model the problem.

You are looking for a short answer but its going to be a combination many things presented in a 3+ column table (bullet 1, bullet 2, and minimum to penetrate the plate). Many combinations of the variables will cut thru the plate. Many combinations will not. You can make the bullet out of steel and shoot it a 500 fps and it may not. You can make the bullet out of wood and push it to 20k fps and it might. Its the "package" that does it, not any one or 2 individual things. It could even be just the angle of impact, or the shape of the bullets, or whether that area on the plate had been hit before!

Edited October 3, 2012 by Jonnin

[atlas3025]

Got pics of the holes? Good close-ups. I'm curious.

Unfortuantely, I do not. I dropped the plate off this morning to get the whole welded up. I only use the plate at 100 yards, so I'm not worried about that spot begin softer, should i turn out that way. Hole was uniform all the way through, with a bit of a ridge built up around the entry hole, and the same around the exit.

This is a multivariable equation that is very difficult to eyeball. You have the energy (effectively, damage done on impact), momentum (effectively, the difficulty in making it change directions, or bounce off), the relative hardness, thickness of the target, the bullet material's tendency to break/splat/frag vs staying together, and more. All these and more have to be examined to understand the big picture. I kid you not it would take me a solid month to model the problem.

You are looking for a short answer but its going to be a combination many things presented in a 3+ column table (bullet 1, bullet 2, and minimum to penetrate the plate). Many combinations of the variables will cut thru the plate. Many combinations will not. You can make the bullet out of steel and shoot it a 500 fps and it may not. You can make the bullet out of wood and push it to 20k fps and it might. Its the "package" that does it, not any one or 2 individual things. It could even be just the angle of impact, or the shape of the bullets, or whether that area on the plate had been hit before!

Yeah, I agree there could be many variables. If I didn't want to pay to fix my plate again, I'd set up some experiments!

[mikegideon]

Unfortuantely, I do not. I dropped the plate off this morning to get the whole welded up. I only use the plate at 100 yards, so I'm not worried about that spot begin softer, should i turn out that way. Hole was uniform all the way through, with a bit of a ridge built up around the entry hole, and the same around the exit.

Yeah, I agree there could be many variables. If I didn't want to pay to fix my plate again, I'd set up some experiments!

Sounds like he already did the experiment . I've been scratching my head on this one too.

EDIT: Just looked up that bullet. Fairly heavy cavity wall and Lubalox coating. Less head scratching now.

Edited October 3, 2012 by mikegideon

[atlas3025]

Well, I don't know what kind of armor a Bradley has, but I don't know how safe I would feel in one with an e-tip equipped Fudd hunting near me. I suspect it would have eat through a half inch plate just as easily.