I've been chatting with Axel Müller (troubleshooterberlin, the guy who built the top loading Remington 11.) about a problem he had with his custom hammer springs taking a set after a few rounds and needing to be replaced. I sent him information on spring stress relief to keep the springs from setting so quickly and he told me that it didn't work.
I for one am stumped.

Probably as much a design flaw as it is a tempering issue.      You have to design any part to work withing the performance parameters of the chosen material, otherwise you can expect a high failure rate.   Spring tempered steel doesn't like to be stressed beyond the limits imposed by its alloy composition and shape. 

Probably as much a design flaw as it is a tempering issue.      You have to design any part to work withing the performance parameters of the chosen material, otherwise you can expect a high failure rate.   Spring tempered steel doesn't like to be stressed beyond the limits imposed by its alloy composition and shape. 

^THAT

Springs are tricky little SOBs. Strength is determined by the thickness of the wire, travel (and consequently where you push them past the elastic limit) is a matter of how many coils you have.

Odds are he needs more coils on his spring, and if that won't fit he needs to make room for a longer spring.

it's a torsion spring, so to get more coils he'd need thinner wire...

Can he go to a larger diameter with the same number of coils? It's basically about using a longer wire.