I just put a Wolff extra power hammer spring in my Mini-30 last night. It turned out to be easier than I had thought, took about 5 minutes.
I used a small vice to compress the spring on the strut. I positioned the captured spring side of the strut on one jaw & the bottom half of the spring inside the other jaw. I slowly compressed the spring with my hand over it to keep it from launching until the hole in the strut was exposed. I then inserted the short end of a hex key into the strut hole. Replace the assembly, cock the hammer, remove the hex key.
Hopefully, it will have the extra force needed to set off the Norinco ammo I've been using.