"Small Arms of the World" and the Mosin-Nagant

I've owned a copy of Small Arms of the World for a very long time. It is a reference book that is sometimes referred to as the bible of early to mid-20th Century military small arms. The 12th and apparently last edition was published 25 years ago. In the writeup about the Mosin-Nagant M91/30, the book discusses a feature of the Mosin-Nagant called a "cartridge- valve- interrupter" or something like that. SAOTW said that no other rifle had or needed such a device.

I think SAOTW had it badly wrong.

First, consider the cartridge used by the Mosin-Nagant rifle. The 7.62x54R cartridge is a rimmed cartridge, like the .303 or the .30-30:

If you have ever loaded a box magazine for a .22 rimfire rifle or pistol, you know that one of the critical things to do is to make sure that when you load the cartridges, the rim for each cartridge inserted is in front of the rim of the cartridge beneath it. Otherwise, when you try to chamber a round, the rim will hang up on the rim of the cartridge underneath and jam the weapon.

The interrupter on a Mosin-Nagant separates the top cartridge in the rifle's magazine from the ones underneath it, so that there is no contact between the top cartridge and the one below it. It does not matter in Mosin-Nagant, therefore, if the round to be fed into the chamber has its rim behind the one underneath it, for the interrupter will make sure that the rims are not in contact and the cartridge will feed.

This is important for two reasons. Whether the rifleman is feeding in ammunition into the rifle in haste or in the dark, he doesn't have to make sure the rounds are placed just so, load them in and keep shooting. Second, combat ammunition is usually loaded in stripper clips.

That's not a Mosin-Nagant, but the concept is the same. You insert the stripper clip in the top of the rifle and you press the rounds down into the rifle's magazine.

Then you throw the clip away, close the bolt and keep firing. If you don't remove the clip, the bolt of most rifles will just push it aside anyway.

Stripper clips have no "up" or "down". The interrupter permits you to load rapidly, ignore which way the rims line up, and keep shooting. It was a good design.