40mm Grenade Maintenance Part 3

In part 3, Coop focuses on the older Moscart brand 40mm shells.

To read part 2, click here.

The quest continues.  I did about 20 more shells this afternoon, given that work was closed due to the snow day.  I promised pics of the Moscart type shell, since they are the first and oldest type you may encounter.

Moscart shells came in 2 varieties, the 24 BB variant with the domed top, and the 96 round variant with the flat top and more barrels.  I will be showing off the 96 rounder, because that’s what Tascabe has in his inventory.


It unscrews just like any other shell (rather, any other shells unscrew just like the Moscart!)

There are a few other fiddly bits to deal with compared to the modernized/simplified design.

From left to right:

The Valve (similar in design to the modern/simplified ones)
Ball Bearings (8 3mm bearings instead of 4 4mm bearings)
The “outer ring” (which I believe keeps everything centered and prevents BB’s from rolling down into the valve.  This piece has been replaced by added material inside the cup/shell/brass.
The “inner ring” acts as a guide for the valve.  It also has a groove cut out inside one end, which is what permits the bearings to slip, allowing the gas pressure to overcome the valve and escape.
The spring is thinner than the modern grenades.
The button pretty much remains unchanged.

There are a few extra steps in ensuring the continuing operation of Moscart shells.  The button must fit and slip in and around the valve, just like in the modern version:


The valve, must however, fit and slip in and around the “inner ring”.  You can actually see wear on this valve from where it meets resistance.

A special note about the inner ring.  The groove inside the inner ring is only on one side, seen here, closest to the camera.  It can be installed backwards/upside down, however the grenade will not work, the button will be physically stuck, and the valve will remain open causing gas to vent.  When assembling the moscart shell, this groove must face toward the barrels… so if doing the upside down method of re-assembly that I prefer, the front of the grenade faces down, as does this groove.

So, if needed, file the inside and outside of the valve so that the button slips in and out of it, and the valve slips in and out of the inner ring.  You’re not looking to dramatically change the inner and outer diameter of the valve, but just reduce the resistance between unlubricated parts, so that when everything is greased up, it works reliably.

Let’s begin re-assembly.  Start with the front half of the grenade.  Since this is a 96rd moscart with a flat face, it stands up on it’s own.

Grease up the o-ring on the valve, the same way done on the modern shells in my first post.  Grease each ball bearing hole, and insert 2 ball bearings in each hole.  This is where things get fun.  They will want to slip in and out, even with the grease, so just take your time and try to keep the valve pointed down.  Once done, press the valve into the barrel assembly.

With the valve in place, lay the outer ring in place.  It is curved “upward” to catch the BB’s in the barrel.

Place the inner ring into the gap between the valve and the outer ring.  The inner ring will rest on the outer ring, and remember to pay attention to the groove inside the inner ring.  In this photo, it is oriented properly, facing toward the barrels.


Drop the spring and button in place.  It will orient itself with some assistance when you screw the cup/brass back on.  You may have to reach into the bottom of the cup and poke the button into place, or use Exarach’s trick of sticking a ballpoint pen through the cup and into the hole of the button.

Next post touches briefly on fill valves, the other failure point on these devices.

To read part 4, click here.