8mm Mannlicher M.17 Incendiary

What was the reason for producing the Austrian M.17 Incendiary round in two caselengths - the standard 50mm and the extended 55mm?

Since this cartridge was obviously for Aircraft Use, in MGs of a Schwarzelose design, ( aircooled) the Violent chambering and feeding action would require better Neck support for such a sensitive Projectile (?Phosphorus filled?).

And being restricted to Aircraft MGs, a simple Chamber ream to lengthen the Neck of the chamber would be a simple matter; and it would not affect firing Ball ammo in a Lengthend neck chamber.

Just my mechanical take on the Problem…

Doc AV

Makes good sense, thanks Doc.

As per Mötz the 55mm case was not all that uncommon and the first ones were made around 1908 already. Back then for the particular use with the new AP projectiles which were much shorter than regular ones and so the neck had to be extended to make up for the proper OAL.

Mötz is also mentioning the specialty of the 8x50R chamber which allowed to chamber cases with lengths of 48-60mm.

The M17 later in wartime required a longer neck in order to cover the exit hole for the WP load as that hole was located almost in the middle of the projectile, so the case neck was extended to safely cover the soldered hole. (vol1, page 239)

Mötz is also stating that the 55mm case was known to cause malfunctions in machine guns.

There was more use of the 55mm cases but that is a lot of reading in Mötz’s great book(s).

Thanks EOD. I believe that these Austrian loads are prone to neck cracks due to the powder swelling so I intend to pull the bullets, it will be interesting to see where the soldered hole is located on the bullet with the shorter caselength.