# Please define the differance in TMJ & FMJ



## Firethorn (Nov 1, 2004)

Im having trouble understanding the difference. 
Thanks


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## AngieM2 (May 10, 2002)

And I'm curious as to what those initials mean.


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## Joyfullyplain (Jun 18, 2008)

Are you referring to the medical/dental condition?


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## maxny (Aug 18, 2008)

I found this explanation on a gun forum those abbreviations are in reference to the outer shell of lead bullets ....hope it helps

"Full Metal Jacket" -
FMJ - has a true "jacket" and also an exposed lead base. During bullet formation, the copper jacket cup is loaded with lead from the back end, then the copper jacket is formed to create a small lip over the rear edge to lock the jacket around the lead center.

"Total Metal Jacket" -
CMJ/TMJ - have no exposed lead. The lead bullet is electroplated with a thin layer of copper. They are not "jacketed" as a FMJ is. Reloading data for CMJ/TMJ bullets is different than for FMJ. Usually, a load specification about half way between lead and FMJ bullets is used.


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## deaconjim (Oct 31, 2005)

*F*ull *M*etal *J*acket - The tip of the lead is exposed
*T*otal *M*etal *J*acket - No lead is exposed


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## AngieM2 (May 10, 2002)

Well, learn something every day.


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## Firethorn (Nov 1, 2004)

LOL, I did not expect anyone to wonder what I was referring to . But your right, TMJ is also a medical condition. 
Yes, ammo is to what I was referring. Thanks Jim and Max. 
So with that info I have another concern. How much of a concern is there to lead exposure with FMJ?


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## zito (Dec 21, 2006)

Firethorn said:


> How much of a concern is there to lead exposure with FMJ?


Well, I guess that would depend on if you were exposed to it pre- or post-fired 

For what it's worth, I usually wear surgical gloves while reloading, but I'm probably just being paranoid.

Zito


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## Wisconsin Ann (Feb 27, 2007)

Lead has to be inhaled or ingested to actually be harmful. Lead Paint is harmful in 2 ways: 1)kids licking the paint and 2)paint flaking into the dust you breathe. Lead in pipes is harmful because of the particles that get into the water. Lead in ceramic dishes because acidic foods can leach the lead, and cutting on a lead glaze can form chips.

Simply touching lead will not get it into your system. The skin is a wonderful bandage on the whole body.

however, if you melt your own lead for bullets, you could be inhaling lead fumes. so...a good mask would be needed.

Lead is very dangerous for kids because it lodges in growing systems and stays there..it's absorbed more easily, apparently.

Using gloves is an easy precaution that doesn't hurt...but probably (note the probably) doesn't help.


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## Ernie (Jul 22, 2007)

Full metal jackets and total metal jackets came about, from my understanding, through the Geneva conventions on warfare. Lead comes apart and fragments very easily inside a human body making it extremely difficult to remove. The armed nations of the world got together and agreed on specific ammunition loadouts to be used to reduce the overall death toll during wars. There's no point in killing a soldier with lead fragments when he would be removed from the battlefield just as efficiently by a jacketed round.

In warfare, the goal is to accomplish objectives, not to kill. Many weapons are designed to incapacitate an enemy as opposed to killing him. There's an old saying: "It takes one soldier to bury him and two to carry him." Meaning a severely wounded soldier ties up more enemy resources than a dead one, making it easier overall to win the war.


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## maxny (Aug 18, 2008)

My understanding is that FMJ bullets are used because the copper outer shell helps prevent the lead from fouling the barrel of the gun. I believe it is the agreed upon bullets according to the Geneva Convention for army's to use. FMJ bullets don't shatter and fragment when it enters the body.


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## Cascade Failure (Jan 30, 2007)

FMJ to the jaw can cause TMJ...:shrug:


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## woodsman (Dec 8, 2008)

Prohibiting the use hollow point of expanding bullets in civilized warfare thought up by the late 19th century gentlemen didn't mandate the use of any other specific type of bullet. These gentlemen could not imagine what human mind is capable of conceiving when it comes to maiming or killing a fellow human. We now have tumbling bullets, as one example, which can cause far greater damage than expanding or hollow point ones and still comply with the Hague Convention of 1899.


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## Cabin Fever (May 10, 2002)

What about lead versus steel. I've purchased two lots of bulk surplus NATO 7.62x51 ammo for my M1A. These cartridges have steel (copper jacketed) bullets. Will the steel damage the rifle bore?


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## 7.62mmFMJ (Nov 19, 2008)

The FMJ has a true copper sheath, or jacket, around the lead core. This is only possible by pouring the lead into the jacket from the bottom thus leaving lead exposed. The copper jacket does a few things: provides positive feeding in military arms, does not expand or fragment when it hits flesh in most cases, keeps the firearm cleaner i.e. prevents lead fouling. 

The Total Metal Jacket, as described above, is copper plating and not a copper jacket as we know it. This leaves a much weaker "sheath" but does cover the bottom of the bullet to encapsulate the lead. TMJ rounds are for practice only. 

Wisconsin Ann has the 411 on lead exposure. For you guys it will take the lead out of your pencil. However, that level of exposure is pretty darn severe.


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## 7.62mmFMJ (Nov 19, 2008)

Cabin Fever said:


> What about lead versus steel. I've purchased two lots of bulk surplus NATO 7.62x51 ammo for my M1A. These cartridges have steel (copper jacketed) bullets. Will the steel damage the rifle bore?


If the steel was exposed to the barrel it would damage the barrel.

The copper jacket acts as a soft, bearing surface to protect the barrel. 

Be careful with the steel cores as not much stops them down range.


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## BRYAN (Jul 5, 2008)

There is steel jacketed ammo on the surplus market that is softer than the steel in gun barrels. These bullets are often "copper washed" with a micro thin layer of gilding metal to lower the friction and reduce corrosion before use, but the steel jacketed bullets themselves do not significantly wear the bore more than jackets of gilding metal because they are softer than the barrel. Greater concern to the barrel is the corrosive primers often associated with this surplus ammo. As a point of clarification, jacketed bullets are not poured or cast into jackets, they are swaged under great pressure.


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## radiofish (Mar 30, 2007)

Cabin Fever - The FMJ steel-cored projectiles (bullets) will not cause harm to the rifleing in the M1A barrel.. The copper jacket on the projectile is designed to prevent scoring and rifleing damage inside the barrel.. That is why there are all of those new foaming bore cleaners, for removing copper fouling from barrels.....

Of course those steel cored FMJ rounds would be more likely to disable a vehicle's engine much easier that, a lead cored projectile..


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