Sealing mystery?

[Old Man Dave]

I stripped down a “spare” Maori mamba 90 the other day. Partly as I was told that it wasn’t holding full pressure and partly just to see what the insides looked like. It is based on an Omer 90 but not sure what model. I believe the 11mm internal barrel and piston along with the complete front end are Maori but the back end is original Omer.

All was fairly straightforward except I was puzzled by a couple of things. It seems as though the plastic nose cone was screwed to the front housing with a silicon sealer or similar on the threads. I surmise that this is to ensure the vacuum is maintained when loaded as there is no O-ring. It could have been that the front end of the barrel threads where they screwed into the front housing also had a sealing substance, but not sure. All other joints were “dry” as they had O-rings. Well all except one and that’s what really puzzled me.

The plastic handle moulding is sealed at the rear to the barrel by the filler valve assembly. This is basically a bolt with the head hollowed out and threaded to accept the pump and the body of the “bolt” contains a ball valve and spring assembly.

The thing is I couldn’t see how the bolt/filler valve sealed to the plastic handle unit. It screws into the inside of the rear of the barrel behind the trigger sear. There are no O-rings. There is an aluminium ring on the shank of the bolt. It almost looks as though it could be a ferrule as used in compression fittings. The seat inside the plastic handle also has a slightly raised lip. To be honest I couldn’t see either of these sealing the joint but somehow they do. At first I thought the lip was an embedded O-ring but it isn’t. Then I thought I had somehow lost an O-ring but I hadn’t and it does seal.

Got me a bit stumped this one. Can someone put an old engineer out of his misery? Please.

Dave.

 

[DivingDane]

think the handle is from he Omer scorpian! maybe the barrel etc as well?

or maybe its just the OMER tempest handle?

DD

 

[popgun pete]

There is no "O" ring seal, or rubber washer seal, used at the back end of the "Sten type" rear handle pneumatic spearguns. The air-tight seal there relies solely on the rear step, or flange, of the metal inlet valve body pressing firmly against the flat annular plastic seat moulded into the rear of the plastic handle. All the various clones seem to be the same as the Mares guns in this respect. Provided that there are no radial scratches in the plastic the large contact area there provides the necessary seal once the muzzle is screwed up tightly enough. On these guns the inner barrel acts as a clamp which holds the front and rear plastic sections of the gun together; the muzzle threads provide the means to tension this clamp and hence crush the inlet valve body flange tightly into the rear of the plastic grip. You can also do it by screwing up the rear inlet valve body, but it is easier to just nip this up first and leave the main tightening (or tensioning effort) to the muzzle, that way you do not twist the barrel inside the gun. There are plastic lugs or tabs to stop the inner barrel turning, but these lugs can be broken, I have done so during my earlier gun dismantling efforts!