Saturday, October 9, 2010

Benjamin 3030 Disassembly, Part 1

I picked this Benjamin 3030 CO2 BB “rifle” (since it isn’t rifled) up on Gunbroker. I was always intrigued by the design and the advertised ability to “drive steel bb's clear through both sides of a 5 gal. steel pail at close range”. Why I’d want to do that isn’t the issue.

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The rifle, rusty and dirty.

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The wood looks like it could use a refinish.

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The metal is pitted so I’m not sure what I’ll do. Probably paint it.

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It cocks similarly to the Crosman 700/707 which it seems to share a similar mechanism with.

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That’s the end of the 8 gram CO2 bulb sitting inside the cap.

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Remove the stock screw.

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Simple trigger.

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An old rusty CO2 cartridge.

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The cartridge seals here below the neck.

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All that debris makes for a gritty trigger.

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Two pins retain the trigger and spring.

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Rear sight.

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Removed.

More to come...

Wednesday, October 6, 2010

Gamo PT 80 CO2 Cartridge Seal

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

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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.

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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?

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Drilling the seal hole.

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Turning down to diameter.

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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.

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Seal in place.

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

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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.

Monday, October 4, 2010

Gamo PT-80 Disassembly, Part 5

Last post…

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The valve assembly removed.

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

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The valve snaps out of the strap.

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

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Hmmm… none of my other tools fit.

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1/16” thick cold rolled steel…

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Fancy tool…

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Unscrewed.

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Seal and valve body screw.

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

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

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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.

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A pretty stout return spring.

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

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Other end showing the teflon seal.

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The washers were a stack of 3.

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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.

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

Sunday, October 3, 2010

Gamo PT-80 Disassembly, Part 4

On I go…

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The Hammer mechanism is a little complex.

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Notice the position of the hammer spring.

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Hammer removed.

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

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Notice the spring.

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Lift it off.

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The spring.

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More detail of the parts, in case.

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

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Removed and the transfer bar is finally almost exposed.

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Removing the valve assembly.

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Now the transfer bar is free…

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

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The spring is unhooked by rotating back.

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Leaving this in the grip frame.

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Pulling it up, careful not to lose the spring.

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It’s a fairly stout spring.

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Brass inserts in the grip frame.

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Front view.

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