Why Are Copper Bullets "Deep Penetrating" if They Are Lighter...?

J

Joshua 2415

New member
I often see comments or advertising that says copper pullets are deep-penetrating. But, isn't copper lighter than lead? Don't we use heavier bullets when we want more penetration?

If you have a 125 grain copper bullet, and a 125 grain lead bullet, then being the same weight, does the copper bullet really give deeper penetration? If so, what is the technical explanation for this?

And will it "hit" harder, or softer, than a lead round of equal weight? That is, will there be any difference in energy delivered on target...better? worse?

I'm considering using the Buffalo Bore 125 grain Tactical XPB (Copper) Short Barrel round in my 357 magnum. Just want to understand this copper thing better.

Thanks.
 
The lead bullets deform and mushroom, which greatly reduces penetration.
Copper bullets do much better at retaining their 'bullet shape' and slipping through tissue.
 
See above comments, plus, if you have a 125gr. lead bullet and a 125gr. copper bullet, they weigh the same. Yes, copper is a lighter material, so it has more mass (longer) to achieve the same weight, but it weighs the same.
 
They also dont shed weight like lead or jacketed bullets can
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This is the key. I have more experience with rifle bullets so I'll answer with examples I know about. Typical lead bullets lose 50% or more of their weight at impact. Some of the better bonded bullets may only lose 20-30%, some of the more explosive designs 80%. A 180 gr bullet @ 3000 fps from a 300 magnum might only weigh 100-140 gr after impact.

I load 130 gr copper bullets in my 308 @ 3050 fps. At closer ranges the impact speed is the same, but the 130 gr copper bullets will still weigh 130 gr after they impact. Penetration and performance on game is about the same.

As mentioned earlier bullet length is a factor. The 130 gr Barnes TTSX's I use are about the same length as 165 gr lead bullets. Longer bullets, even in lead penetrate deeper than short bullets.

The same principle applies to handguns, but I don't think the difference is quite as dramatic. At slower impact speeds lead handgun bullets don't shed weight like faster rifle bullets.

Copper bullets do much better at retaining their 'bullet shape' and slipping through tissue.
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Somewhat true, but this is one of copper's disadvantages. They need speed to expand. You generally drop down to a lighter copper bullet and shoot it as fast as possible. If they impact too slow you get little or no expansion. Since you don't need the weight for penetration, go lighter and faster with copper for best results.
 
Yes, copper is a lighter material, so it has more mass (longer) to achieve the same weight, but it weighs the same.
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A copper bullet has a greater volume than a lead bullet of the same weight. It has the same mass.
 
A pure copper 125 bullet is much larger than a 125 lead bullet. Because of this case volume is reduced which all things equal will increase pressure.

It's for this reason that JHP's with a lead core can be driven harder than pure copper bullets.
 
Typical lead bullets lose 50% or more of their weight at impact.
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In the context of the handgun forum, this statement is somewhat misleading.

The statement is accurate when applied to simple cup & core rifle bullets travelling at relatively high velocity.

These days, using premium (controlled expansion) rifle hunting ammunition or premium self-defense handgun ammunition, it would be pretty unusual to see a 50% weight loss on impact even with a lead core bullet.

Even with fairly simple bullet designs, handgun velocities are generally low enough that it's not common to see bullet weight losses of 50%.
 
I don't know about the 50% weight loss. The handgun tests I've seen on YouTube with lead ammo have never demonstrated 50% weight loss. They haven't even shown 10%. The last one I watched was a 158 gr. lead hollowpoint. It measured in the high 150's after being recovered. I'm not a "ballistics" guy, so I won't claim to know the why's and if's and becauses of it all, but I do know that those bullets didn't come out of the gel at 80 grains.
 
The pictures of recovered copped bullets often show the expanded petals, these have space between them and their edges look jagged and sharp. The things look like pretty good cutters and cutting through things can take less energy than crushing and pushing things aside so more energy left for penetration. No?
 
Mass divided by cross sectional area reflects penetration depth

Taking this to the limit "Assuming" the same mass, an AP round will penetrate further in gel because of the lesser / no deformation properties result in less cross sectional area slowing it down.
Copper will deform a little more, lead more than that (again all other things being equal) and a pressed nickel frangible much less, having the largest cross sectional area after entering the gel / target.

In reality for, ballistics and properties of materials, nothing is linear or equal in real life.
 
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