The $100 challenge.....

I'll be keen to see how you weld up those parts. It's a good idea as there's not a lot of meat in that cocking shoe, and if those parts get a bit more meat in them it should create a more positive action.

Welding is something I know very little about. although I have made metal popcorn trying.

Cylinder repairs completed tonight and ready for reassembly tomorrow night with any luck.  I MIG welded around the perimeter where I'd done the damage and made up an internal spacer to allow me to clamp the soft cylinder wall in the lathe and also align the centre rod I'd removed.  After I'd ground off the excess weld I turned it down to 25.0mm giving me 0.5mm clearance to the the cylinder wall (0.25 all round) rather than the 1.0mm it had originally.  I then reinstalled the rod and  TIG welded then base back into place.  Then into the lathe to clean up the piston seat area taking a little off it as my welding didn't include any filler so eroded away the perimeter edge a bit.  This will however compensate for the extra thickness of the steel top hat.

I took the opportunity while it was apart to polish the inside wall of the piston and the full length of the rod.   Some hand work with the Dremel and a small tungsten ball cutter plus files to clean up the lower edge of the MIG weld and the cocking shoe bearing area followed by polishing of the piston exterior and I'm done.

It's not a particularly pretty sight up close, but I'm sure it will work fine - that's if I remember to assemble it correctly this time around

Well, no shooting tonight either.  I thought I had everything ready for reassembly, but I still couldn't get the cocking shoe located through the slot and inside the piston where it should be.  I did some measurements and figured that I'd managed to shrink the centre swage on the piston even more when clamping it in the lathe leaving too little clearance between the inner wall and the spring.  The next move was to thin down the shoe, but that still wasn't enough.  I managed to find an old piece of pipe of a suitable size, cut and machined it to suit then pressed it inside the piston to gain some clearance.  This worked OK, but of course opened the slot up more allowing one leg of the shoe to be free to disengage if it so chooses.  Out came the files and a slot created on the leading edge so when the cocking pressure comes on it should be firmly locked in place.  Test fitted before I packed up and looking good for tomorrow night.

I really hate the piston design, construction and the material they've used.  The only good thing about it is the centre rod which appears to be hard as hell.  The tube itself though is very soft (tapping the slot edges true with a copper head hammer after I'd spread it left visible impressions in the 'steel'), the extent of the swaging is far more than necessary and the cocking arm slot is too wide.  It's a shame because the cylinder is really quite nicely made.  I'll persist with this part for the time being so I can at least fire a few more shots, but I may yet resort to making my own from a piece of pipe and utilising the original centre rod and base. 

Has anyone been able to shoot some half-decent groups at 10m??  I got my gun back together tonight and it's silky smooth so I'm really happy about that, but I'm still struggling to get any semblance of a decent group.  Thinking about it as I'm typing - perhaps it is the red dot (Hawke)?  I did some sighting in at 6m and got a very tight group initially, but it just went haywire when I went back to 10m.  Different pellets are going in completely different directions with a wide scatter.  The mount is rock solid, so I'm off the sports shop in the morning to see if he has a Nikko Sterling in stock.  

There's a very noticeable misalignment between the barrel and cylinder centrelines so there's not much point in fitting the Tasco until when & if I get around to truing that up.  The bore looks nice and straight and the rifling also looks good.  I must be getting a bit of grease coming through though as I can smell it.  Perhaps it's dieseling and causing this issue?