Talk:Full metal jacket (ammunition)

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The article on the F.M,J, (Full Metal Jacket) may leave the misimpression that bullet jackets were developed to comply with the Hague convention. The Hague Convention sought only to distinguish "ball" or solid bullet ammunition from hollow point or other expanding or fragmenting ammunition. As the name implies, it does not matter whether the solid bullet is jacketed or is quite literally an old-fashioned round lead ball.

The Hague convention was concerned with the morality of using more damaging expanding and fragmenting ammunition in warfare. This moral issue has been revisited in modern times as police agencies observed that Hague compliant solid nose bullets were far more likely to ricochet or over-penetrate a legitimate target, endangering innocent bystanders. Fragmenting ammunition is considered a must for Air Marshals to minimize the risk of damage that over-penetrating Hague compliant ammunition would do to an aircraft. The original Hague Convention’s concern over the excessive lethality and wound damage from expanding and fragmenting bullets seem almost laughable in light of the subsequent use of gas and explosive munitions in World War I.

Jacketed bullets were not developed to meet Hague convention criteria, but rather the full metal jacket variation of the jacketed bullet is made for this purpose and for reliable rapid loading in automatic and semi-automatic weaponry. To illustrate this distinction, jackets are found both on soft-nose and hollow-point expanding hunting bullets and in hollow point target shooting bullets. The difference is the copper alloy cup from which a jacket is formed sees its solid bottom become the bullet base in hunting and high quality target shooting bullets, while it becomes the bullet nose in full metal jacket bullets.

For accuracy, as in target shooting, the precision of the bullet base formed is more critical than the precision of the nose shape. The dies that form the jacket control shape more precisely than those forming the lead alloy core, which is why the best target shooting bullets also have hollow points. Target shooting bullet nose hollows are too small to expand and because their jackets are too thin to hold together on impact, these bullets are also banned from warfare under the Hague convention.

The main reason metal jackets were developed was to stop bullet metal from stripping off in the rifling of a gun barrel at high velocities. Even with modern lubricants and copper gas checks on their bases, lead alloy bullets cannot be fired at much above 2000 fps without fouling the barrel. By comparison, modern jacketed military ball ammunition achieves muzzle velocities from over 2500 fps (7.62mm NATO or .308 Winchester) to 3200 fps (5.56mm NATO or .223 Remington). Because a bullet’s kinetic energy is the product of half its mass and the square of its velocity, the possible velocities for jacketed bullets over those of lead alloy bullets are disproportionately significant to their terminal behavior.

Some exceptions exist for special alloys containing silver or other expensive additions, but generally speaking a copper jacket alloy will have a Brinell hardness scale number of 100-130, while lead alloys typically achieve Brinell scale numbers under 30. The hardest alloys contain a lot of antimony and tin, thus lowering their densities over that of pure lead.

The fouling from firing lead alloy bullets causes inaccuracy, and so requires cleaning too frequent for modern battlefield conditions. It can even accumulate enough to cause dangerous chamber pressures. Rapid firing can cause barrels to get so hot that cast bullet fouling solders to them. The heat of powder combustion causes the residue of the lubricants necessary to shoot lead bullets to build up a lot of soot. For machineguns this fast accumulating cause of jamming would be an impossible limitation.

The lower velocities possible with lead alloy bullets limit their long-range use. The lead alloys are too soft to withstand rapid feeding without deforming a pointed nose. This means the best ballistic shapes cannot be made of lead alloys for any but single loading rifles. Metal bullet jackets address these shortcomings plus allow the bullet’s core to be nearly pure lead. This maximizes bullet density and with it, momentum in flight. The result is better long-range accuracy with less wind drift in flight.

In summary, jacketed bullets were developed to address the velocity, fouling and feed limitations of lead alloy bullets. The ability to form them to create non-expanding FMJ ammunition to comply with the Hague Convention is a variation of the technology.

[The preceding unsigned comment was made by 69.47.46.103 on 2004-11-27.]

As you seem to have extensive knowledge of the subject, your contributions to the article would be most welcome. You are free to edit it whenever you please. AlexanderWinston 16:32, 2004 Nov 28 (UTC)

Is there any source claiming that FMJs are effective in combat BECAUSE they create an injured solider instead of a corpse?

There could be, but they'd be wrong. SkonesMickLoud (talk) 13:55, 4 March 2010 (UTC)[reply]

Not necessarily. When you have an incapacitated soldier, you potentially take 2-3 individuals out of the firefight if they are busy providing aid or removing them from the battlefield. It does need to be sourced, though. nf utvol (talk) 16:35, 3 February 2012 (UTC)[reply]

One point that should be addressed is the tendency of pointed FMJ bullets to yaw and tumble after impact with a soft target. In some cases, especially the 5.56 NATO's M193 and M855 rounds, it causes the projectile to fragment after penetrating a few cm into the target and greatly increases the wound severity over what one would expect from a bullet that traveled point-first. — Preceding unsigned comment added by 2001:470:E27C:FE:608F:7749:E75E:2E5B (talk) 15:25, 29 August 2016 (UTC)[reply]

I reworded the History paragraph because the previous version made very little sense to me; I hope that I didn't inadvertently introduce any inaccuracy (I know nothing about this subject) in my interpolation. -- EmmetCaulfield 13:46, 28 May 2006 (UTC)[reply]

Are ball and metal case the same as full metal jacket? --Leif Runenritzer (talk) 19:50, 11 August 2008 (UTC)[reply]

"Ball" is. No idea about "metal case". Never heard that one before. Faceless Enemy (talk) 07:08, 31 May 2010 (UTC)[reply]

I've only ever heard metal case refer to the actual brass casing of the cartridge, usually in reference to shotgun shells (as opposed to plastic or paper casings).nf utvol (talk) 16:13, 29 December 2011 (UTC)[reply]

Remington uses the term "metal case" and occasionally "full metal case" in their advertising copy and technical material to describe this type of bullet. I do not know whether any other manufacturer uses those specific terms, however. — Preceding unsigned comment added by 68.61.156.96 (talk) 02:45, 14 February 2012 (UTC)[reply]

"Metal case" is used to refer to bullets jacketed via electroplating. The jacket is significantly thinner, and the jacket completely encloses the bullet's core material, whereas FMJs tend to have the core material exposed at the based of the bullet. "Metal Case" is synonymous with "Total Metal Jacket." — Preceding unsigned comment added by 73.215.111.97 (talk) 08:10, 27 October 2016 (UTC)[reply]

Should there be a reference to TMJ? I came to Wikipedia to find out what TMJ was and all I got was a redirect to FMJ with no explanation. An external site states that FMJ (Full Metal Jacket) is a jacket from the tip down the sides, but not covering the rear of the bullet. TMJ (Total Metal Jacket) totally envelops the bullet, including the rear.

Stargzer (talk) 02:27, 23 January 2018 (UTC)[reply]

I converted the redirect to a description of the differences between electroplated and swaged jackets. Thewellman (talk) 05:48, 23 January 2018 (UTC)[reply]

This section is largely unreferenced, and seems somewhat misleading to begin with, especially the following section:

Hollow point and soft tipped bullets are for use against soft targets only, such as animals or people, whereas Full Metal Jacket bullets can be indiscriminately used against soft and hard targets, delivering sub-optimal damage to both kinds of targets. Jacketed bullets require a certain velocity for proper expansion based on its size, and larger quantity of gunpowder must be needed. They are the most expensive followed by plated bullets and last cast. Jacketed bullets are also bulkier, heavier and a handful to carry because they have a bigger volume and occupy more space. Rifles using this bullet must have large fitting magazine and speedloader capacity to insert it easier.

It reads like a descrition of FMJ rounds in a video game, not reality, such as comments about them being the most expensive (they're the most produced, so in reality, they're often the least expensive to purchase), bulkier and heavier (not necessarily, some non-FMJ rounds can be heavier, such as cast bullets, because lead is heavier than copper), and being a "handful" to carry (many soft point bullets have negligible differences in dimensions in comparison to FMJ rounds). The whole last sentence about needing larger magazines and speedloaders has nothing to do with FMJ rounds.

Anyway, going to be rewriting this section and getting rid of most of the current content if there are no objections.nf utvol (talk) 16:30, 29 December 2011 (UTC)[reply]

"Ball Ammunition" redirects to this page. If it's going to redirect, it should be explicitly referenced somewhere in the article as an alternative name. Thistledowne (talk) 23:04, 2 December 2014 (UTC)[reply]

Removed unreferenced work, corrected Hague Convention myth, and tried to re-word with focus on the projectile, not the cartridge. Added "Ball" ammunition reference. Severely cut POV sections. Changed "Disadvantages" to a more neutral explanation of "Impact Characteristics". This article could use some good graphics showing the differences between the styles of jacketing, instead of lots of pics of cartridges with the same kind of jacketed bullet. It's like showing different cars to illustrate tire design details. BeadleB (talk) 18:42, 24 May 2015 (UTC)[reply]