So I got my project gun

[Craig-P]

Exciting stuff, Nick - I’ve replied to your PM mate

[NickG]

Got a bit more done https://photos.app.goo.gl/AnrM8zksNNYvDko38https://photos.app.goo.gl/48wVwYANBqcEwgLm8
Just a top hat and I can get it shooting, will make a cast iron piston ring before I build so I can test with both .

[NickG]

So made a top hat and a cast iron ring (two actually) and couldn't get them into the groove the o ring dimensions are too big for the cast ring to work,so made a synthetic one from the precious material I have been using in the tx
Built it all up with a tx spring , but needed a lot of pre load, and it made 11.2 with 7.9 and 10.8, with exacts only had 4.53 to hand I think it would do 11 on 4 .52, this is on the standard transfer port. The tx spring is too close in diameter to the bore of the piston and with the large pre load (50mm) I can feel it catching on cocking, so plan b is a 97 spring smaller diameter and a bit longer .

https://photos.app.goo.gl/g8JVFUNDqYmKMRPy9

[Shed tuner]

sounds like your piston weight will be perfect

[NickG]

sounds like your piston weight will be perfect

Fingers crossed Jon, I can always add a little weight via a steel top hat if needed, I was pleased the sleeve o ring sealed straight off , its a bit awkward to install as its half a groove if you get my meaning, the bottom of the cylinder forms the front of the groove , trying to keep lost volume to a minimum.

[Shed tuner]

Fingers crossed Jon, I can always add a little weight via a steel top hat if needed, I was pleased the sleeve o ring sealed straight off , its a bit awkward to install as its half a groove if you get my meaning, the bottom of the cylinder forms the front of the groove , trying to keep lost volume to a minimum.

...but looking at those numbers, and allowing for a little more preload and a slightly heavier (grams) spring, I can't see you'd need to.

Yes, I get you on the o-ring at the end - I guess you can only shove it forwards during installation

[NickG]

You were right about the spring , adjusted the guides and dropped a 97 spring in, trigger block is now just at the beginning of the thread so about 18mm preload , and its on the money , 11.2 with express and 11 with exacts , had to do a little work on the inletting to accommodate the extra stroke and the sleeve retaining screws, and its in the stock ready to shoot, I have only ever shot an 80 once before , so going to get Craig p to shoot it this weekend as he has probably shot a lot of them, see what he reckons to it.
So got to pretty it up now ordered some tube for a barrel sleeve and muzzle weight, and I have a nice two stage adjustable blade somewhere ? to go on it.