Cometa 5 rebuild - seeking input

[AR1911]

Christmas 1960 Santa left me a new Cometa 5 airgun.  I used and abused that as only a prebuscent boy can.  But I've saved it all these year with the intention of repairing and rebuilding it.  Time to get started!

Issues include:  Bent barrel, damaged rifling, poor breech seal, probably damage from dry-firing. Numerous cosmetic issues.

The plan is to:

Replace the barrel. I compared my Benjamin barrel to the Cometa, and it looked like it was close enough. I bought a new barrel assembly from Benjamin.

Question:  How can I swap the barrels?  Do they press out of the breechblock? 

Rebuild the power unit. I'm sure the piston and seal are trash, so I expect to make or adapt something once I see what I have.

Question:  It appears the aft end of the receiver, which includes the trigger housing, is threaded on. I tried it but normal force would not budge it. Before I get "creative", and I missing something?  Suggestions?

Is there any chance OE parts are available for this old gun?

Beyond the above, I'll be repairing threads and generally cleaning up the machine work, which is quite rough.

[Roadworthy]

The piston and seal are probably not trash.  The gun is old enough that the seal is probably leather.  Get some silicone oil and drip a few drops into the transfer port then stand the action up vertically until you figure out what to do with the barrel.  This will allow the silicone oil to soak into the leather seal.  They can frequently be rejuvenated this way.  As far as the barrel goes - you usually replace the barrel and barrel block as a unit.  The barrel in the block CAN be replaced but I haven't a clue how.  This is probably a job for a machine shop.

[SteveP-52]

It's not much but here's a few parts and pieces at least:

https://www.gunspares.co.uk/products/24324/5/

[AR1911]

Thomas, good advice on the seal.  I think I'd still like to take a look at that piston to assess the condition.  As to the barrel, I do have machine tools, and I'm somewhat skilled in their use. I am hoping these will press  apart.  Worst case I could machine the old barrel out of the breech block and size the new barrell for a light press fit, and also pin it.   

[AR1911]

Steve, some of the parts shown do not match up with mine, such as the rear sight.  Internal parts may be the same. Good to know there are some parts available.  Thanks!

[anti-squirrel]

If the barrel is bent to where it kinked, you'll have to replace it.  But if it has just a slight bend, I'd say bend it back.  You can either do the "jam it between tree limbs" type of bending or fabricate a square frame  out of wood and then use a bottle jack to press it back.  I did this with a Crosman Optimus and the current owner uses it exclusively for squirrel hunting.

[AmBraCol]

AR1911, I'm curious if you're still around and if so, how did your project turn out. I'm contemplating a Cometa 5 that came up for sale here in Coffee Country. It appears to be a newer version than yours. They changed a few things (sights, for example) over the years, but apparently all of the versions had a screw in trigger block.

[AR1911]

AmBroCol, I have not made any progress. Project is still shelved for lack of a Round Tuit.

[AmBraCol]

Wow! Talk about a blast from the past!  The reshuffling of the forum to place threads in appropriate categories makes for some interesting looks at the past - and maybe a nudge to get old projects up and going again, or at least try to remember where they are in terms of progress (or lack thereof).  I'm trying to remember what all I did to my Cometa 5.  At the moment I think it's just replace the seal with a synthetic using an adapter a friend with a lathe cranked out for me. Haven't shot it in a while. It is a fun little plinking platform!

[AR1911]

Looking back through this thread, I can provide a few updates.
I did succeed in removing the barrel by pressing it out.  This was a bit problematic as the breech face is not at 90-degrees to the bore.  Also there was a hidden pin that I overlooked. That was destroyed when I pressed the barrel out. Fortunately the barrel and breech were harder steel so no damage done, other than the pin.
The Crosman barrel I bought is the correct diameter for the breechblock, so that part is good.

I am going back with the synthetic piston seal. I did make a new support washer between the seal and the screw. 
The piston bore looks a bit rough, so I'll need to address that. Brake cylinder hone probably.

I'd like to find a new spring, and possibly a polymer sleeve to enhance stability.

 I also found breech seals that will work, I may end up cutting the recess to install a wider seal.  The OE setup just seems insufficient to me, especially as the mating surface is roughly machined. I will try to smooth that out, which may require that bigger seal.

edit: I did get the receiver apart. I was indeed threaded, but it took some serious persuasion to break it loose.
I will need to build a spring compressor at some point.

I continue to be amazed at the roughness of each part. It's as if they were hand-made by an apprentice with a dull file and a bench grinder! I hope to improve on that.

Thanks for the interest. I'll try to find time to proceed with this project.

[AmBraCol]

Hey, Rex!  I had a quick look at mine today. I suspect 1970's or 80's vintage, but don´t know for sure.  I believe Cometa improved their quality over time as their more recent offerings tend to be nicer in the area of finish and fit.  For a spring, you might get your hands on a spring from Crosman. I'm fairly sure the springs intended for the Optimus could be cut down and used, but if you would take measurement of your spring wire and such I'll be glad to compare it to a Crosman spring I've got on hand.  Going to synthetic seal made all the difference in consistency in my rifle.

[Struckat]

Have you contacted Cometa to see if they have parts?