That is a really nice H&R! I have a small collection of "Saturday Night Specials", in .32 and .38 S&W calibers, none are nearly so well preserved as yours. I have one each of H&R, Iver Johnson, Hopkins & Allen, Forehand & Wadsworth. Such a small revolver must naturally have very small parts and yet the hammer needs to fall with the same impact of a bigger gun. They generally fall into the "just barely work" category when new. Your problem may be nothing more than old oil that has turned to varnish. I'd suggest you first try flushing it out with WD-40 to see if that may free up the works, it may not be a broken spring but just a tired and weak spring, as I said, they just barely work when new and although your gun is very well preserved it is far from new.