Gem Piston Washer Replacement

[DCL_dave]

Hi

I have a Gem that had a big screw holding a rotten leather cup washer when I eventually got it apart!

I've cleaned them up here, Had a hell of a job removing the screw as it was siezed in place!


The gun was a heck of a mess, Paid a tenner with the .25" spare barrel, Was going to make a stock but found one on Mel's table at Melbourne for a fiver!!




I snapped the trigger guard/cocking link whilst tring to get the piston to move, Luckily it came with a spare on the other barrel (Can't use that one as it's not a T bar Gem!)..



Plenty of emery cloth, Draw filing on the flats of the barrel and I got it shiny!!




I then messed it up trying to cold blue it!!




I should finish it really, Can't even remember where it is now


John

Hi John,

Looks like a nice EG No9 spoon lever type? (possibly...something looks funky though)... and parts of a JM No2 Tbar.

Edit: The lever is reversed mounted over barrel instead of the cylinder as depocted in the EG catalogue.

[DCL_dave]

You can see how the piston head is ground and polished for a perfect fit in the cylinder. Not usual for a piston with seal fitted .

Baz

Agreed Baz, that JM piston started life as a machine fit piston, the large screw and leather washer are probably later additions to fix a worn piston seal.

[Benelli B76]

With my Gem I found that fitting a piston seal dropped the power by reducing the swept volume.

Baz

[johnbaz]

Hi John,

Looks like a nice EG No9 spoon lever type? (possibly...something looks funky though)... and parts of a JM No2 Tbar.

Edit: The lever is reversed mounted over barrel instead of the cylinder as depocted in the EG catalogue.

Hi Dave

The nickel plated spoon lever type I bought from our Mel on here, The piston with the strange screw is from a T bar

John

[Benelli B76]

Picked up a couple of interesting items today including a .25 plain bore German Gem. Stripped it to renovate and it had the usual piston which uses no piston seal, just a centering hole used during manufacture.

Baz

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[Stefran61]

John

Alot of effort gone into it so yes maybe you should dig it out and complete it.
The piston leather seal arrangement is very similar on mine, undecided on whether to mess with it or leave as is, as pointed out previously a modification that can reduce efficiency. This will be more a shelf hanger than functional I think.

Has anyone got a metal butt plate going spare??

Steve

Hi

I have a Gem that had a big screw holding a rotten leather cup washer when I eventually got it apart!

I've cleaned them up here, Had a hell of a job removing the screw as it was siezed in place!


The gun was a heck of a mess, Paid a tenner with the .25" spare barrel, Was going to make a stock but found one on Mel's table at Melbourne for a fiver!!




I snapped the trigger guard/cocking link whilst tring to get the piston to move, Luckily it came with a spare on the other barrel (Can't use that one as it's not a T bar Gem!)..



Plenty of emery cloth, Draw filing on the flats of the barrel and I got it shiny!!




I then messed it up trying to cold blue it!!




I should finish it really, Can't even remember where it is now


John

[Benelli B76]

I think the best result would come from glueing a thin disc of polyurethane onto the piston head using Tigerseal. I will turn up a 2mm thick disc that is a good fit to the cylinder. This way the air seal should be improved without a big loss of swept volume.

Baz