I know it is old thread.
However....
"Hi all,

The subject of this ammunition has come up on various forums, and quite alot recently, so I am posting this in order to debunk the misconceptions (which seem BOUNDLESS) about this ammo.

Firstly, it must be stated at Hirtenberger Patronen (HP) is an ammunition company like any other. Just because someone has obtained Hirtenberger ammunition in 9mm Parabellum (Luger), does NOT mean it is the submachine gun ammunition. HP produces many loadings in 9mm Parabellum (Luger).

Many people have erroneously believed that HP's 124 gr. +P+ (usually marked "HV") rounds are the "submachinegun" rounds- and this is flatly incorrect. These rounds are designed for pistols, whereas the SMG rounds are not.

Hirtenberger has produced two types of SMG ammunition. Both were developed on request for the British Ministry Of Defence:

L7A1- This ammunition was produced between 1990 and 1992. Many samples exceed the NATO maximum chamber pressure specification for small arms, which is 50,000 PSI (345 MPa). For this reason, the British MOD ceased to use it. It was replaced with:

L12A1- This ammunition is substantially similar, but uses a slightly reduced charge in order to stay under the 50,000 PSI NATO maximum pressure specs.

Both of these rounds feature a 124-grain FMJ ball bullet, and produce a maximum velocity of about 1,500 fps.

Contrary to popular belief, these rounds were not designed for arctic conditions, nor were they developed for the Sterling SMG. They were designed for use in H&K MP5 series SMGs. Although they were undoubtedly tested under arctic conditions, the use of the term "adverse conditions" in its designation is more euphemistic than anything else.

In terms of the commercial availability of these rounds, the MOD released 12 million rounds of L7A1 ammunition as surplus. Since the ammunition is packaged in a 1,200 round case, this means that 10,000 cases were released. Since HP refuses to sell this ammunition to the public, and only produced L7A1 in 1990, 1991, and 1992, and only for the British contract, that means that the entire world's supply consists of 10,000 cases.

Likewise, within several months of release, BATF banned the importation of the ammunition, due to its being unsafe for use in handguns. This second fact makes the ammunition even more rare in the United States.

If offered this ammunition for sale, view the offer skeptically, as the above-mentioned facts limit the actual availability of such ammunition- and likewise, a considerable amount of the ammunition imported into the United States has undoubtedly been fired already by its owners.

Beware of attempts to sell ammunition which is falsely advertised as " Hirt SMG ammo ". Many dealers, either due to ignorance or fraudulence, will sell standard Hirtenberger ammunition and claim that it is the SMG rounds.

L7A1 ammunition can be identified by its headstamps:

'HP' (for Hirtenberger Patronen)
'90', '91', or '92' (year of production)
'L7A1' (ammunition type)
NATO proof mark (a circle with a cross inside)

If the headstamp doesn't contain "L7A1", it is NOT the SMG rounds.

Some forgeries of this ammunition have been produced in other nations (particularly in Darra, Pakistan, where many forgery firearms and ammunition are produced for the black market). The easiest way to tell that the ammunition is forged, is the absence, or poor application, of a red sealant ring around (and slightly onto) the primer.

Any ammunition marked "L12A1" is either a forgery or stolen, since HP produces it exclusively for British MOD.

The only other manufacturers of "SMG" ammunition (to my knowledge) are:

Israel Military Industries (IMI), who produce the ammunition packaged in either plain brown boxes or boxes with the " UZI " logo. These rounds are black-tipped, but the black tip designates them only as high-pressure, not specifically as SMG rounds; and

Remington, who have produced a 9mm SMG round loaded with a standard JHP (not Golden Saber) bullet. Any company advertising Remington SMG Golden Sabre rounds is falsely advertising.

Note that Remington only produces the SMG rounds on a per-request basis, and only for government agencies. Likewise, IMI produces the SMG ammunition rarely (mostly for Israeli and American military contracts) and very few samples of it are in circulation in the US, mostly in the hands of collectors.

SMG-specific rounds are NOT SAFE to fire in any handgun. There are a few handguns designs which can tolerate it SPARINGLY, but I do not recommend this practice. Remember, the SAAMI maximum chamber pressure for 9mm +P rounds is 38,500 PSI, and the NATO maximum chamber pressure for small arms, including rifles, is 50,000 PSI. SMG-specific rounds meet or exceed the 50,000 PSI mark.

Note also that SMG rounds are likewise unsafe to fire in many submachineguns, and virtually all pistol-cartridge carbines, since both are usually engineered for 9mm pistol ammunition. Only a very few models of carbines and submachine guns are suitable for firing the ammunition in; if in doubt, contact the manufacturer and ask them about the use of L7A1 ammunition in their guns."

Found this info on the net.

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Memento mori