Tony DeMurray’s MMM Mondial Roger BB Pistol Repair

Tony DeMurray sent me the following showing his repair of his MMM Mondial Roger BB Pistol:
MMM Mondail Roger BB Pistol
Since parts are difficult, if not impossible to come by, workarounds have to be done.
Problem:
Air gun leaks in two places:
Piercing pin
Valve assembly
The reader should refer to Nicholas Carter’s blog pages as to how to disassemble and reassemble the gun. He has great pictures and good commentary.
First, let’s deal with the Piercing pin area.
Since original seals are hard to come by, I used one from Walther Makarov pistol.

The green end seal is from a Makarov.
This seal requires the center hole to be slightly enlarged to fit snuggly around piercing pin. Also, a little sanding to reduce the outer circumference is needed for a good fit. (I’ve read where some put pipe tape around the threads of the collar. I did not)
Secondly, let’s move to the valve assembly area.

The original seal was virtually gone.
The stem is pushed out.
The little O-ring in the base discarded. Its function of sealing the back stem inside the cap is not needed.
The cap is ground down to remove any lip. Again, not needed since original valve seal is unobtainable.
Clean the valve stem. Notice the vent opening.
I made a valve seal from 1/8^th Urethane/Polyurethane sheet. (Red)
Cut out a 1” X 1” section from the sheet
The center hole was drilled out to fit around the large part of the valve stem. I used a #3 0.213 drill bit.
(place the collar back onto the valve stem, insert into the drilled hole and circumscribe the outside diameter using an ultra fine point Sharpie.)
This outside circumference including the black ring was trimmed using an Exacto knife.
Do not cut inside the black ring. Trim the outside only enough to allow the seal to fit into the cup cavity.
It is necessary that this seal is a flush fit to the sealing ring inside the valve body.
Assembly the valve stem, seal and cup.Notice how the seal comes up to the vent on the shaft.This is a critically important assembly step.

I drilled a 7/32^nd shaft into a dowel. This tool helped to push the seal around the stem and into the cup.

Notice how the valve stem is almost flush with the end of the cup.
Disassemble one last time.
Put a small drop of metal Epoxy into the small hole. This is going to hold the valve stem in place and seal up that end of the cup. (This is why the little O-ring was no longer necessary.)
Reinsert the valve stem to the original depth. Don’t worry about a little dome of epoxy. The spring will fit over it.

Let cure the appropriate amount of time.

Insert the seal flush with the edge of the vent and level. Do not worry if cup was not ground level.
Insert valve stem assembly into air valve housing.
Try blowing into the piercing pin and moving the hammer. Even if properly sealed, a very small amount of air escape may be notice. The CO2 will supply far greater pressure to fit the seal.
If not, disassemble and reseat the seal again. It took me three tries to get it right.
Reassemble gun. (I had significant trouble getting the barrel out. I took a Dremel tool and ground off the painted surface from the tip and a little more so that the barrel would slide into the housing. The set screw is all that is needed for a firm fit.)


This is very important!
Place the gun in the Open position. This takes the pressure off the hammer.
Pierce a CO2 cylinder. A slight hissing will occur until the neck of the cylinder is sealed by the end seal. Then, the valve assembly will jolt into its sealed and ready position.
Load BBs. And remember, this is not a pure repeater. Each shot requires the gun to be pointed up to drop a BB into the loading chamber.

Roger Mondial Pistol, Finishing Up

So let's see if I can get it to work...

A bit of scotchbrite pad stuck into a split dowel...

Polished up the valve seat.

The old seal was removed. Note the location of the slot, it's important.

Some urethane was machined...just as with all my other seal projects.

I trimmed the seal the the face of the valve cup. This was an error.

I made a rubber washer for the CO2 piercing cup.

Looks ok...

If you've ever worked on CO2 guns you know what this is...a frosty CO2 cartridge...so I had to slip a shim under the piercing seal to raise it slightly...then it did seal against the cartridge. Yay!
But then with a new cart it dumped all the gas through the barrel...Boo!

Here you can see the valve with the hammer resting against the lever.

But with the hammer weight taken off you can see the valve sticks out way further than it could seal. So I had to make a new seal. The key was for the seal to extend to that slot in the valve stem. Sorry I didn't take pics, I was in a bit of a frenzy...
Anyway, with the new seal length it sealed up fine! A fun little pistol even though you have to tilt the pistol back every shot to feed a new bb into the feed mechanism. So it isn't rapid fire and you lose your sight picture.

Roger Mondial Pistol Disassembly, Part 2

On I go.

There's a setscrew that holds the barrel in.

The setscrew.

I pushed the barrel out by twisting and pushing.

The power adjustment mechanism. It regulates the relationship between the valve lever and hammer.

The underside of the grip frame, showing the adjustment screw.

The valve assembly.

Lovely green goo in the CO2 piercing cup.

An 11mm wrench unscrews it.

The piercing pin came out with it. YMMV.

The piercing pin and cup. I love that green color.

The end of the valve assembly.

The end unscrewed. Should I throw in a pitch for using a properly fitting screwdriver?

There's an o-ring to seal the end. The exhaust valve and spring came out.

The exhaust valve and spring.

It's difficult to make out but there's a slot into the valve stem right where the seal is. The seal was toast...

The stem is hollow. Gas flows around the seal, through the slot and through the stem to the barrel, picking up the BB on the way.

The spring for the valve lever. The steel washer bears against the step in the valve stem.

All the parts.

There's a seal I couldn't get out where the piercing pin and cup screws in. It seems fine so I'll leave it.

One exploded gun. Note the large diameter piercing screw and huge brass nut. Forgot to mention those, not that it matters.
I'll blog about resealing it in a few days.

Roger Mondial Pistol Disassembly, Part 1

This is another recent gun show purchase, a Roger CO2 BB pistol made by MMM Mondial. The manual is here, and there's another page on it here.

Not a bad looking piece of potmetal.

Removing the grips.

The other side of the grips have hexagonal countersunk nuts.

As does the frame, molded haxagonal recesses for the nuts.

The 4 screws removed. Don't lose those nuts, and it's a good idea to study which screw goes where...

The sight is a lot like the one on the Daisy 200.

The two screws pivot it on the angle for elevation.

There's a phillips head screw on the other side.

Be careful pulling the frame halves apart...I wasn't and parts got unsettled.

Here's the proper relationship of the parts.

Pulling the trigger pushes back the hammer until the sear slips off the pins, at the same time as the trigger raises the BB feed mechanism.

One more screw holds the valve assembly to the frame.

You can never have too many pictures of the spring assemblies...

Ok, no complaints if you can't get it back together.

The hammer and spring.

The long end fits down inside the slot.

The BB feed mechanism slides up in that slot.

The magnet.

A BB held by the magnet. Exciting!
More to come...