Titan springs were introduced iirc as Titan XS many years ago.....
....As for spring quality the Titan wire is superb, the coating, I have my doudts about it's usefulness tbh, if nothing else it's a sales gimmick!...
....The wire the MK3 spring was made from will be imperial, not metric so 1/8" then? ...
....Pre- load is measured as soon as you start to unscrew the trigger block ie. The bottom of the thread inside the cylinder to the top of the spring after the block is removed...I'm not trying to teach my Granny, it's surprising how many get this wrong!
...
29 coils of 1/8" wire with a free length of 240/250mm will make the spring far too stiff. i think the originals were 225mm with 30 coils. I always removed a coil usually increasing the power a little as the rifle was oversprung right from the get go!
Coils are counted from the first complete turn, find the end of the wire, follow it round & where it meets itself, that's one coil,
LIKE THIS then continue up the spring, when you reach the other end its often part of a coil ie. 0.5 or 0.75 of a coil.
LIKE THIS This is important as it adds to pre-load. Again not trying to teach my granny.
What I suggest is a spring with 3.2mm or 1/8" wire, 26/29 coils with a free length of 190/200mm. Put one M10 steel washer into the bottom of the piston for the spring to twist & try that.
Last time I serviced a MK3 my records tell me I used 26 coils, 190 f/l 3,2mm wire giving a Vo of approx 650fps using RWS Superdome in a .177. Not far from the marketing litrature iirc may be a bit more?
I can soon make one up for you to try.
Cocking the MK3 is never going to be a 2 finger effort, they were never easy from new. I have seen many MK3 cocking levers bent after continual use due to the effort required with the standard factory spring.
Hope this helps.