FMJ composition


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john917v
August 29, 2008, 03:21 PM
What are FMJ rounds typically comprised of, that makes them harder than HP rounds? Anyone fired a (except for the case) completely copper or completely brass/other metal bullet?

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Jorg Nysgerrig
August 29, 2008, 03:52 PM
What do you mean by "harder"? I haven't found FMJs are substantially harder than a most JHP rounds. There or some differences in penetration/expanson due to designs and/or penetrators that might be involved, but for the most part, they are mostly made of the same stuff (aside from metallurgical variations).

Stump Water
August 29, 2008, 03:59 PM
FMJ bullets are composed of copper and lead (lead alloy). They typically aren't any harder than other bullets, but the "full metal jacket" keeps them from deforming as much as other bullet types.

I load/shoot Barnes "X" bullets. They're solid copper.

brickeyee
August 29, 2008, 04:08 PM
Most FMJs use dead soft pure lead.
This allows easy swaging of the lead and jacket.

everallm
August 29, 2008, 06:48 PM
Mainstream hollow points are swaged as well and made with the same materials.

You will see some minor metal/alloy differences between the varying manufacturers recipes depending on where they source their stock.

Plated rounds can be more susceptible to mechanical damage as the plating can be really thin in comparison to a "standard" FMJ

kurts_armory
August 29, 2008, 10:05 PM
the jhp is meant and designed to expand upon impact, whereas the fmj is designed for penetration. some of the fmj's i have seen are alloy instead of copper.

230RN
August 29, 2008, 10:08 PM
You do mean the jacket itself, don't you?

Working purely from memory:

Used to be that jackets were made almost exclusively of what is known as "gilding metal," an alloy of copper and tin, which was developed as follows:

A long time ago the French used to add tin flakes to their artillery shell powders to eliminate the copper fouling caused by the pure copper rotating bands on their shells.

Sometime later, when copper jackets for small arms became commonplace, the copper fouling became really severe with the higher velocites attained in these small arms, especially near the muzzle, where the bullet was moving fastest.

The military started to add tin flakes to small arms powders to alleviate the fouling problem. To differentiate these from the regular powders, a "1/2" was added to the powder designation.

For one of the 1920s National Matches, Col Townsend Whelen developed a copper jacketed bullet which was plated with tin.

This was called "Tin-Can" ammunition, and apparently shot very accurately, and almost completely eliminated the fouling problem, but was quickly withdrawn from the matches because despite explicit instructions to the contrary competitors insisted on dipping the bullets in grease for lubrication. This practice was known to increase pressures disastrously and several Match rifles were "broken" because of the grease on the bullets.

After that, I believe it was Winchester-Western who discovered that the same effect would be obtained by alloying the copper jacket material with tin directly. This product was called Lubaloy (for "lubricating alloy", also known as gilding metal), and could be used with either full-metal jacked bullets or soft-point hunting hunting bullets, the advantage being the reduction in jacket material fouling, not any other magical property of the material.

Nowadays, the jackets of FMJs can be made from very soft ("mild") steel, but are usually "copper-washed," meaning lightly plated with copper.

Variations in "hardness" may be due to either the thickness or exact composition of the gilding metal jacket material or to the annealing methods and thickness of steel-jacketed bullets.

Whether they are FMJs or hollow-points or soft-points.

Note that even steel-cored bullets (as opposed to the steel jackets) have a thin layer of lead between the jacket itself and the steel core to allow the bullet to be engraved by the rifling.

Again, strictly from memory. Anyone can feel free to correct or add to this story of bullet jacket materials.

General Geoff
August 29, 2008, 10:17 PM
Some milsurp ammo is steel core, but that has little to do with jacket type.

I've never fired any monolithic solid bullets (other than lead), but they do exist, made out of copper, tin, and a few other materials, mostly for very high performance long range cartridges like .416 Barrett, .338LM and .408 CheyTac. I'm sure there are some MS bullets for .50BMG as well.

Artiz
August 29, 2008, 10:32 PM
Anyone fired a (except for the case) completely copper or completely brass/other metal bullet?
MAGTECH makes a 100% solid copper hollow point bullet called MAGTECH FIRST DEFENCE, for law enforcment.
Available in most handgun calibers like 9mm Luger or .40 S&W.
No jacket to tear away that generally cause loss of effectiveness and power.
This bullet delivers deep penetration and devastating expansion.

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