Have any of you tried a spring setup like the following...excerpt from Diamond Tooling. Nested compression springs: Sometimes, you'll need a compression spring that's stronger than any single spring can be. In that case, you can make nested compression springs — one spring inside the other — that will be a lot stronger than a single spring. Some automobile valve spring assemblies are actually nested springs, so are the suspension springs on railroad cars. Nested compression springs are easily designed: just remember two things:Nested compression springs must be different-handed. If the outer spring is right-handed, then the inner spring must be left-handed, or vice-versa.The outside diameter of the inside spring CANNOT be larger than the inside diameter of the outside spring. If it is, the springs will not nest.
As a follow up ... Years past as mentioned by Hector, the Diana 75 GISS match rifles had them.Tho inner spring ran on an internal guide independent of outer spring guided on I.D. of pistons.
Here's the 380 with 2 springs shown. Update...sent worn out spring to Diamond, we'll see what they come up with.