Diana Giss advice needed

[NeilnrLincoln]

Some brilliant information on here, thankyou. I'm a lot more confident in the workings of the Giss system now.

[abellringer]

Have to agree with the comments and good advice given by members, there should always be a second thin shim in the end cap on rifles, and the small retaining screw is indeed fitted after the end cap is tightened up, as is evident when you first strip an Original and find swarf in the rear piston head [if it's still in enough pieces to see]. The smaller diameter is definitely fitted into the cylinder, the timing is needed to be:- when the springs, pistons, cogs and covers are fitted; and the pistons are at rest under spring pressure, you offer the end cap up to the rear piston washer and look for a tiny gap between the cyl. end and the front face of the spacer, there should be a gap of 0.3mm [ factory instruction]; this ensures when the end cap is fitted tightly the rear piston is pushed forwards slightly, this takes the pressure of the mechanism and gives the cog ''freedom'' described in several posts. This freedom is needed, as has been said to avoid stripping cog and piston teeth.
Hope this helps.

[NeilnrLincoln]

Thankyou, that sounds exactly how mine is set up now. Just enough preload with the end cap tightened up to take the load off the cogs. There is no shim fitted under my stepped washer though & I've put a dab of loctite on the end cap as my locking screw doesn't line up.
Had a shoot with it this afternoon though & it's soooo smooth!
I need to overhaul the model 65 that I've just bought, where's the best place to buy seals, Chambers? And is there anything else I should be replacing as a matter of course while it's in bits?
Thanks.

[Benelli B76]

Strange thing is in all the Giss systems I have done, the rear balance seal has not had the dreaded bacterial degradation. The only reason I can think of is that any oil that has been added through the transfer port has only reached the front compression seal. Older type polyurethanes degrade and break up especially through moisture and humidity. When I sold it in South Africa in the 70's it used to turn to "cheese" on our warehouse shelves. Later polyurethanes have additives to protect them.

Baz

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[NeilnrLincoln]

So the blue seals from chambers will be an improved material & last pretty much forever? Is it worth changing the springs or just leave the originals if they're not broken?
Do you lube the gears & springs in giss guns?

[dvd]

So the blue seals from chambers will be an improved material & last pretty much forever? Is it worth changing the springs or just leave the originals if they're not broken?
Do you lube the gears & springs in giss guns?

I got the parts from Germany. Google Waffencenter-Gotha. There's a chap called Enrico, communicates in English as well, very helpful and prices are decent.
You can get a complete overhaul kit for around 30 Euro.
Springs in giss systems are sided and one end has the wire end sticking out so that it seats against a spur in the middle of the spring guide. They practically
last for ever because they are very long and unstressed.
I have had 25 year-old springs that had only set by 12mm compared to the new ones. They were just as good, but if the old ones are kinked, replace them as a complete set of 3. Make sure you have a spring compressor because they are long and kink easily if pushed unsupported.
Lubrication of the gears and springs is best if hardly any is put on. I use molybdenum grease and wipe it off so that there is hardly any left. The cogs are just idler gears and if set up correctly, they are never loaded except when in the cocked position without the end cap screwed all the way in.
Too much lube causes unwanted drag and slows the pistons down.
Unless the gun has been opened before, the threaded parts may be very stiff to undo. Be weary of using the two holes for the pin spanner in the end cap and gear covers. I use curved jaw locking pliers and very thick leather on unopened guns. After that pin spanners are ok.
One last thing, do not use excessive force when doing up the threaded parts.