My experience is that most S&W revolvers are shipped bone dry. And most have burrs on the internal parts that slow the hammer speed enough to hamper function. Older guns like your 17 and 18 can be dry too, or worse, have congealed/hardened oils slowing things down. I use good old rubbing alcohol on the internals and a toothbrush plus compressed air to remove the old stuff before re-oiling
If you have not done it already, take off the side plate and look for an arc inscribed by hammer burrs on the side plate or under the hammer on the frame. The burrs are easy to clean up with a fine india stone.
Then give it a good dose of a full synthetic gun oil like Slip 2000 and let it saturate at least overnight.
Since this is a K frame, check if the leaf spring adjust screw is bottomed out. If there is room to screw it down a bit, do that before you go shopping for new leaf springs.