9 mm Prabellum OAL question

[unspellable]

It has been brought to my attention that the SAAMI mximum OAL for the 9 mm Parabellum (Luger) cartridge is the same as the original DWM minimum OAL.  Any body have any idea why this cartridge shrank?

[John Traveler]

The 9mm Parabellum cartridge is an old one, first standardized by DWM before adoption of the Parabellum ("Luger") pistol by the German Navy in 1905, and then the German Army in 1908.

At that time, the standard bullet was a truncated cone FMJ, copied today by Fiocchi and others.

WWI combat use of the truncated bullet round in "snaildrum" Parabellum magazines was found to be unreliable, and the FMJRN became the standard bullet.  The RN load was longer than the truncated cone load to improve feeding reliability in submachine guns and pistols.

SAAMI used the longer RN specification no doubt because 9x19 pistols and submachine guns had long standardized on it.

HTH
John

[unspellable]

Unfortunately you have the matter backwards.  The SAAMI MAXIMUM OAL is the same as the original DWM MINIMUM length, not the other way around.  It's a major contributing factor in the Luger's reputation for supposedly being unreliable.  The Luger magazine requires the nose of the cartridge to ride on the front of the magazine rather than resting on the cartrdige below.  Hence, short cartridges lead to magazine hang ups.
This may require a truncated nose bullet to be seated out a bit further out than a round nosed bullet.

There is no currently loaded US round that is even as long as the SAAMI maximum let alone long enough to meet the original specification.

The mystery is why SAAMI shortend it.  About the only effect of reducing the OAL would have is to increase the pressure in a cartridge that is already running fairly high pressures by handgun standards.

We have been conducting an extensive research project into what makes the Luger work or not work and the one question we have no answer for to date is why SAAMI shortened the OAL.

(Incidentally, on contacting SAAMI I found they couldn't explain any why's or where fors about either the 9 mm or the 7.65 mm Parabellum cartridge.  Makes you wonder.)

[John Traveler]

OOPS!

I re-read my posting and you are right!  I worded it wrong.

I meant to suggest that the RN bullet loading was longer because the truncated cone loading impacted on the feedramp too soon, reducing feeding reliability.

Why the scarcity of info on the 7.65 P and 9mm P?? Why did US manufacturer's standardize on the shorter OAL?  

Maybe because at the time (1925) the SAAMI organized these cartridge/chamber dimensions, there were no US-made guns chambered for either 7.65 P or 9mm P.  So, the OAL of the shorter bullet was copied. They were all European (German) manufacture.  Sure, the "American Eagle Parabellums" were available, but they were imported.  

Similar mistakes were made, including the 7mm Mauser which through oversight or translation of engineering documents, chambers ended up with SAAMI dimensions several thousandth's of an inch longer than the German standard and cartridges shorter than standard.  Firing US 7mm Mauser ammo in early Remington rolling block rifles for example, gives unsatisfactory case life due to this incompatibility.  Even recent NATO arms production shows these differences:  European 7.62x51 chambers and bore dimensions have subtle differences from US standards.

If I remember correctly, as late as WWII, only S&W made a 9mm P gun, and that for an ill-fated machine carbine rejected by the British.  S&W didn't build 9mm P pistols until the M39 in the early 1950's.  NATO standardization didn't start until the 1950s, and the 9x19 NATO was much later.

I'd be interested in the results of you P studies, if you care to share them.

John

[michbob]

J Traveler:

Do you have any info on the ill-fated S&W 9mm carbine that the Brits wanted for service in WW2?  I've never even seen a picture of one.

Thanks.

Michbob.

PS:  Was the truncated cone bullet of the early 9mmP the same one the Italians used in the 9mm Glisenti?  With less powder, of course.

[John Traveler]

Michbob,

I don't have a scanner, but will try to send you a pic in a few days.  The S&W 9mm carbine was a shoulder-fired weapon, with a large magazine box (2x longer than stick magazine) in front of the trigger guard.  I've only seen a couple in shops and gun shows in the last 30 years.  It was an awkward, clumsy weapon, and too bulky for its range and power.  "History of S&W" by Roy Jinks shows pictures of it, and I believe some older "Guns of the World" also show it.

After rejection by the British purchasing commission, S&W negotiated a deal to supply .38 "Victory" revolvers rather than refunding the R&D money.  The rest is history.  In the late 1960's-early 1970's crates of these new, unfired S&W carbines were found in storage at the S&W Springfield, MA factory.  They were bought up by collectors and now reside in private collections and museums.

Yes, the 9mm Glisenti looked a lot like the original DWM truncated cone 9mm P.  It should.  The Italians made a lower powered close copy of it for their service pistol.  I don't know if the dimensions, weight, etc were exact but 9mm P service ammo can be chambered, but should not be fired in Glisenti pistols.

[unspellable]

The first cartridge for the Luger was the 7.65 mm Parabellum, a shortened version of the 7.65 mm Borchardt.  Next came the 9 MM Parabellum.  There were two or three engineering models before it reached the production version we are all familiar with.  Most people think it is the 7.65 Parabellum necked up, but the available evidence suggests it was actually developed directly from the 7.65 Borchardt and is not a necked up 7.65 Parabellum.  Not a really important point since they all have the same case head.

The first production 9 mm load did have a truncated cone bullet.  This was changed to a round nosed bullet during WWI.  By most accounts this was because of concerns with the Hague accord and had nothing to do with function or reliability.

The 9 mm Parabellum was originally loaded to a velocity that gave it an impulse very close to that of the 7.65 mm Parabellum so that it would work with the same flat recoil spring found in the Old Model Luger.  With the introduction of the New Model Luger and a coiled recoil spring, two different springs were used for the 7.65 mm and 9 mm.  This allowed the 9 mm to be loaded to a slightly higher velocity.

The Glisenti was originally chambered for a cartridge very similar to the 7.65 mm Parabellum if not the same cartridge.  I suspect the 9 mm Glisenti cartridge may simply be the original loading of the 9 mm Parabellum for the Old Model Luger.  This remains to be established.

Today, the Luger is a collector’s item.  It enjoyed the peak of its popularity as an actual working gun in the US during the time between WWI and WWII.  During this time the 7.65 mm out sold the 9 mm in the US.  A variety of bullet types were loaded in the US including hollow points.  (I have a partial box of Winchester 7.65 hollow points in the deep red waxed label box with corrosive primers from this era.)

If SAAMI started their standards in 1925, this would be tens years and a war after the change from the truncated cone to the round nose in the German military load.  We are in the process of attempting to duplicate the original truncated cone bullet for both calibers and will then determine the correct OAL for the truncated bullet as compared to the round nose.

As a side issue, another question with no fully satisfactory answer so far is why the Luger barrel groove and land diameters are oversized.  This oversized condition appears in the SAAMI specs and is found in most 9 mm handguns.  It explains why the Browning Hi Power has a reputation for key holing with cast bullets.

[John Traveler]

I have a Canadian Army armourer friend that may be able to at least partly, explain why 9mm guns frequently have oversize bore and groove diameters.

Some time ago,  I asked what he knew about 9mm STEN gun barrel production, and he gave the following:

British STEN and 9mm Browning High Power pistol production, along with 9mm P ammo were produced in Canada during wartime rush conditions.  The 9mm caliber was chosen for compatibility with Axis submachine gun ammo stocks as well as the types of weapons (subguns) desired.  It was felt that for the intended use (close range combat), bore and groove diameter specifications could be relaxed to allow for longer barrel tooling life.  FN engineers provided the drawings and expertise to set up the John Inglis factory in Montreal for HP production.

A second consideration was that the 9mm P is a high-pressure pistol round, and that the oversized bore and groove specs provided functional safety margins in handling both UK and Axis production ammunition.  

These factors were already applied to Axis production of the M1935 HP at the FN factory, DWM, and elsewhere.  Tigher bores and deeper grooves also has the additional benefit of increased barrel life, particulary in submachine guns.  You find these practices in recent use as in UK, FN, German, NATO, etc use of tighter bore and groove specifications for 7.62x51 weapons.

[unspellable]

The original Luger barrels were nominally oversized.  They were made during peace time conditions and were held to very tight tolerances.  We have measured quite a few Luger barrels and find that they actually do fall within the tolerances given on the drawings.  The oversized condition does not seem to be a question of tolerances, but rather quite deliberate.  War time production Lugers also seem to have held tight tolerances on the barrel deminsions
i
Today's SAAMI specs call for an oversized barrel.  Probably simply copying the original specs.

The more we learn about the history of this cartridge the more questions we raise.

I would consider submachine gun barrels to be a seperate issue since they place less priority on accuracy and more on erosion and wear.