Gamo PT 80 CO2 Cartridge Seal

I really didn’t know what I was dealing with…

Levering out the brass ring (I used a small screwdriver in the slots) so I could get a better look in the cavity for the seal. Notice the pot metal fracturing. I had to use gravers to remove the excess metal trapping the ring. In hindsight I suppose I could have left the ring in place.

Although with the ring removed I was able to measure for the diameter of the seal. The ring got beat up in the process. I wonder if Gamo just swaps the whole valve assembly when they service the pistols?

Drilling the seal hole.

Turning down to diameter.

Cutoff. The first one I made was about .05” thick, later I made another than was about .04” which worked better. The seal is basically just a flat disk.

Seal in place.

Brass ring pushed in. In theory it should stay put.

Testing the assembly with a used (empty) cartridge. Reassembly of the pistol was in the reverse order of disassembly. I managed to flip the “teflon” exhaust seal around and at first the pistol wouldn’t function, I disassembled the pistol several times and finally realized that I had it flipped. It now functions normally and holds gas. Once I get some clips I’ll test it out and see if there are any other problems.

Gamo PT-80 Disassembly, Part 5

Last post…

The valve assembly removed.

Detail of the piercing clamp screw. The square nut is captured by the grip frame.

The valve snaps out of the strap.

The mostly removed (by a previous owner) CO2 seal.

Hmmm… none of my other tools fit.

1/16” thick cold rolled steel…

Fancy tool…

Unscrewed.

Seal and valve body screw.

It’s probably a flat seal that deformed to fit.

Why not another pic? Odd that it came out looking orange, it’s redder in real life.

The valve stem. Seals against the red seal, when it’s knocked open gas flows from within the valve chamber, through the three radial holes and down through the valve stem.

A pretty stout return spring.

There were washers and a teflon (I’m assuming it’s teflon, could be anything) seal.

Other end showing the teflon seal.

The washers were a stack of 3.

I can’t figure out how to get that brass ring out. You can see a gap between the bottom and the ring where the seal goes. I think that the edges of the valve assembly were staked over it to retain it. Likewise I think the piercing pin was a press fit. So I’ll leave it. A new seal should snap into place if I make it the correct thickness and diameter.

What have I done? Good thing I took pictures. I'll work on getting it resealed soon.

Gamo PT-80 Disassembly, Part 4

On I go…

The Hammer mechanism is a little complex.

Notice the position of the hammer spring.

Hammer removed.

That oversaturated part is the sear? The transfer bar underneath pulls it off the hammer.

Notice the spring.

Lift it off.

The spring.

More detail of the parts, in case.

Hammer transfer unit swung into place in front of the valve stem.

Removed and the transfer bar is finally almost exposed.

Removing the valve assembly.

Now the transfer bar is free…

Headed pin pushed out through the right sideof the grip frame.

The spring is unhooked by rotating back.

Leaving this in the grip frame.

Pulling it up, careful not to lose the spring.

It’s a fairly stout spring.

Brass inserts in the grip frame.

Front view.

Plastic plugs. I’m assuming this is where a laser sight would mount on those versions that come with a laser sight.

Gamo PT-80 Disassembly, Part 3

On I go…

Grip frame halves separated.

I had to lever the halves straight up as the posts on the right side grip frame are a snug fit in the holes on the left side. Notice the CO2 cartridge strap.

Safety, inside view.

Safety, external view.

More parts. I replaced the end of the trigger spring where I think it goes.

Notice the transfer bar that fits between the hammer and the valve stem when the pistol is fired. At rest it sits below. One screw holds the valve assembly to the right half of the frame.

Notice the piece below the hammer and the way the spring is tucked under a small boss. Notice the rectangular bosses that hold the CO2 Cartridge strap to the valve assembly.

Wire arm. connects the trigger mech. to the hammer mech. Again notice the screw that retains the valve assembly.

Another e-clip.

Once the clip is removed the sliding arm is pivoted up and then slides off of the pivot pin.

Trigger and spring.

Pulling off the trigger, notice the smaller spring underneath and what I assume is the feed pawl for the rotary clip?

How I think the spring is retained by the trigger (this would be an underside view).

Pawl removed.

More to come…