What is the influence of overal length?

[Sieger]

Originally Posted by alterfritz

Hello all,

"I would like to ask what is the influence of the overall length of a 9mm cartridge on it's mechanical reliability? Is there a consensus about the "right" length?

"...this reloaded one gave me a bad malfunction during the last few rounds. Somehow an unfired round was chambered and the toggle stayed open, could not be closed and it appeared that the next round was in a position that held the toggle open. I wasn't able to pull the magazine out, but somebody else with more pistol experience helped me and got it out, probably simply by using more force than I did. I fired a magazine of Winchester after this with no problems.

"So my first question is, are these kinds of malfunctions typical with shorter bullets? And my second one is, can anybody explain to me what went wrong mechanically? I would like to understand what caused this jam."

Hi:

With a Parabellum, OAL is a very critical element for proper function (being able to fire, from a full 8 round magazine, at least 1,000 rounds without a jam).

Your mechancal question first. Please note the steep angel in which the magazine sits in the frame. Luger designed the grip for a perfect fit in the human hand at a price, that being, the aforementioned steep angel of the magazine. The cartridges just don't move upwardly, as is the case with the P-38 or Colt 1911, rather, they "slide up" the interior of the magazine at a very steep angel. This sliding action is one reason the spring of a Luger's magazine needs to be so incredibly strong as compared to a P-38 or a Colt 1911.

With proper OAL, all 8 of the cartridges are perfectly alligned, in a parallel fashion, within the magazine, and there is no binding during the feeding (sliding) process. With the OAL too short, you will note that the top cartridges cant downward just a bit. This slight cant downward causes a split second delay in the upward movement of the top cartridge upon firing, causing just the jam you have described above!!

Here are your proper, original DWM specification OALs:

Round nose 9MM and 7.65: 1.169 to 1.173

Truncated Cone 9mm: 1.14 to 1.15

If you reload, try these lengths in your MecGar Magazines, as they will work perfectly. Yes, these lengths are way too long by modern reloading manual standards, as most commercial loaders of modern 9mm ammo have lost touch with the need for the in spec. lengths for the Parabellum pistols.

Yes, proper powder type and charge are also necessary to make a Luger function properly, as well as, in spec. magazine and main springs.

Sieger