Sweet shooting 77k ‘recipe‘?

[lightning22]

Just for completeness the original thread https://www.airgunbbs.com/showthread...ighlight=Hw77k

[prosport.177]

Indeed venom lazaglided pistons did have the rear bearing carrier brazed on, all the ones I have seen have 3 Delrin buttons drilled into the bearing carrier to reduce metal too metal contact. V mach pistons had the arrangement like in the pictures with a circumference bearing.

Steve pope would be the only one to say when he stopped using the delri n buttons on piston and started using the circumference bearing same as on tx200 pistons..

[lightning22]

Bringing this one up to date, I got the metalwork back from Paul Chell today, beautiful doesn’t fully describe it.

On the mechanical side the TP will only just accept a 3.8mm drill shaft, but it won’t slide all the way through so the port is the wider end of 3.7mm in diameter.

I swapped on a prototype from Mike Hall, out of the box it feels a little looser in the bore than the Aussie seal, but compresses well with my finger over the transfer port, right to the point when it shot one of the delrin buttons out with a brisk leak of air.....

Sooo, I’ve got a leaky cylinder which may be why it was as slammy as it was before it went off for rebluing. So, now need to make sure it is degreased and dig out the loctite 271.

[Shed tuner]

if the cylinder is leaking that's not easily fixable. Either get a replacement cylinder, or (especially if it's a 26mm), sleave it down to 23mm. Now that'll be a sweet shooting gun

[lightning22]

Hi Jon,

It’s a 25mm, the leak seems to be a pinhole so I’m sealing the end plug with loctite a-la the HW35 fix, I’ve forced it into the void under pressure so now have to let it set and see how it goes.

[HW777]

I've read about the odd com tube leaking

Is yours leaking because of a drilled button dimple in the com tube

[lightning22]

I've read about the odd com tube leaking

Is yours leaking because of a drilled button dimple in the com tube

Yep, the button is within the area occupied by the end plug so it isn’t like there’s a hole in the side of the cylinder, the air is leaking through whatever method has been used to fix the plug (threaded etc?).

By sealing it with loctite I’m hoping to stop the leak, I’ve got nothing to lose in trying.

[HW777]

Yep, the button is within the area occupied by the end plug so it isn’t like there’s a hole in the side of the cylinder, the air is leaking through whatever method has been used to fix the plug (threaded etc?).

By sealing it with loctite I’m hoping to stop the leak, I’ve got nothing to lose in trying.

Keep us updated, if it does not work I have another suggestion to try and sort it

[lightning22]

Keep us updated, if it does not work I have another suggestion to try and sort it

Ok, thank you.

[Shed tuner]

ahh, I get you now. yeah, should be fixable as you said if it's fully in the end plug region, and a 25mm defo worth saving. could even braze or weld it from the outside if the loctite doesn't work ?

[lightning22]

ahh, I get you now. yeah, should be fixable as you said if it's fully in the end plug region, and a 25mm defo worth saving. could even braze or weld it from the outside if the loctite doesn't work ?

That would be very much a last option, the thought of me poised over it with my MiG doesn’t bear thinking about!

I blasted it out with carb cleaner last night and dropped in some 271, I’ll get a 25mm dowel with sandpaper glued to the face down there today and clean up the face of the plug. It was surprising how much muck was down there considering it’s just gone through the bluing process and will have been boiled in caustic soda to remove grease etc.

The replacement spring I got from Knibbs is 3.2mm and longer than the Titan, it would also need guides making or modifying as it’s narrower internally. Once sealed I’ll get it up and running with the original setup and see if it shoots better with only one transfer port..

[Shed tuner]

That would be very much a last option, the thought of me poised over it with my MiG doesn’t bear thinking about!

I blasted it out with carb cleaner last night and dropped in some 271, I’ll get a 25mm dowel with sandpaper glued to the face down there today and clean up the face of the plug. It was surprising how much muck was down there considering it’s just gone through the bluing process and will have been boiled in caustic soda to remove grease etc.

The replacement spring I got from Knibbs is 3.2mm and longer than the Titan, it would also need guides making or modifying as it’s narrower internally. Once sealed I’ll get it up and running with the original setup and see if it shoots better with only one transfer port..

brazing probably safer I have solder valves and things up before, whcih seems to hold in the long term (tiny holes).

Apparently that caustic boiling dislodges a lot of crud in 77 tubes, and rumour has it that many owners feel a degredation in performance whilst waiting for all those newly exposed voids to fill up again...

Never experimented with more than one transfer port, but I'm pretty sure extras won't help performance

[HW777]

brazing probably safer I have solder valves and things up before, whcih seems to hold in the long term (tiny holes).

Apparently that caustic boiling dislodges a lot of crud in 77 tubes, and rumour has it that many owners feel a degredation in performance whilst waiting for all those newly exposed voids to fill up again...

I was going to suggest silver soldering And it sounds like hot blue is a little unfriendly to com tubes

I just cold blue them as the part once in situ never gets handled to wear the bluing down

[prosport.177]

I was going to suggest silver soldering And it sounds like hot blue is a little unfriendly to com tubes

I just cold blue them as the part once in situ never gets handled to wear the bluing down

That was exactly what I was thinking.. silver solder as it really flows beautifully.. But everything has too be clean and grease free..

[lightning22]

Well, the 77k is back together..

It certainly feels better as well as definitely looking better it’s currently running the following spec;

Titan Xs spring at standard length, Prototype , Paul Short transfer seal, fitted guide and top hat. Glided internals lubed up with chain lube on the spring and some sparing smears of bumslide moly lube.

https://drive.google.com/file/d/1yU0...w?usp=drivesdk

https://drive.google.com/file/d/1fPR...w?usp=drivesdk

It has a very quick action, but not slamming like it was, so sealing the end plug seems to have done the trick. I’ve only put a few initial shots through so a little early to break out the chrono just yet, plus it’s a Combro which is always a challenge on something with a foresight/catch like this.