H&R 929 revolver-soft hammer strike

[hunter63]

 Picked up a H&R 929 revolver, looks like new, not even any scratches or worn bluing…..But
I’m getting a soft hammer strike, so all the chambers don’t fire all the time.
Checking out the main spring part number 24a on schematic from Numrich gun parts,
http://www.gunpartscorp.com/catalog/Products.aspx?catid=7927
The one that is in there appears to have been cut…..has the plastic top piece on it.
So ordered a new one that looks the same….but when I got it, seems too short and pretty much falls right out.
They do list a metal top assembly, so was wondering if the plastic part is maybe the wrong part?
Any ideas?