Twenty years ago I had a shade-tree gunsmith fabricate a new leaf spring for my great grand dad's Parker VHE boxlock. He tempered the spring by putting it in a flaming puddle of motor oil in a coffee can. I've put probably 500 shells through the gun since without a hiccup.

It was easy enough service. He lived at the end of my country road and accepted a bottle for payment. I'd recommend him to you, but for him being on the wrong side of the grass now....