nitro476:
To suggest that anyone on this board would tighten a gun by "throwing a burr or two upon the pin or the hook" is an insult to our collective intelligence IMHO.

I have tightened three pommie doubles by TIG-welding and re-cutting the hook, smoking the surfaces to get the fit perfect. Two were shotguns, one a rifle with chopper-lumps but integral hinge-pin. I can assure you that this IS the way to do it! According to Russell Wilkin, Holland's were using this method for many years, but are now getting better with 'metal spraying', whatever that is!

Two of my Brit doubles have been tightened in the distant past by dove-tailing a piece into the hook, possibly in England. ...and guess what! They kill buffalo like lightning!

..and I do agree, 275 USD is right up there for a spring. Making springs is not rocket-science, they used to cost about 60 AUD when Century Arms was operating. I have even made a mainspring myself for an Alex Henry .577 Express. The exception would be Greener 'Empire' main springs, since they double as the cocking-rod and are a bit tedious to fit!

We are all very happy that your double-gun hunting has been so 'civilized' in the past, nitro476, but as 500Nitro has pointed out, some of us do like to get amongst it occasionally!

...sounds like you might have got a bit of sweat on your .470 on that Zim buff-hunt, though!