Webley No 1 Mk III* mainspring

[lifesaver]

Greetings fellow pyrotechnic projection people:

Great to have this resource and appreciate the expertise out there,this is my first post.

I recently purchased a beat up 1918 mark 3* Webley. The mainspring was broken just past the point where it bifurcates. It looks very much like the mainspring of the Webley Mark VI .455 revolver found on the Numrich parts page but its been impossible this far to get the exact spec or a scale pic of that spring. Several references indicate there were a number of interchangeable parts between the revolvers and this flare pistol, which would have made sense in terms of ease of wartime repair.
So- I excercised my limited gunsmithing skills and laboriously filed up a new duplicate spring complete with stirrup, went through the tempering and annealing processes and- ting- of course the damn thing snapped in exactly the same spot as the original. Despite many references including Brownells site,where I got the spring steel, making this type of mainspring is not as easy as it sounds. The labour takes an hour or 2 but the tempering is the real challenge, to get it stiff enough to act like a spring,and not so brittle that it snaps under load. If any members have a Webley Mk III mainspring spring they would like to sell, a source for the spring or other helpful hints I would greatly appreciate the advice. If it turns out there is a chance the Mk VI revolver spring is the correct size then I will likely purchase it from Numrich-although the tech there said he doubted it would fit.

thanks for the help with this problem.