RWS Chamber Lube for my Ruger Blackhawk Springer and Crosman Nitros??

No

Why NO? RWS Chamber Lube is silicone oil for ALL airgun power plants according to Pyramid Air.

http://www.pyramydair.com/s/a/RWS_Air_Chamber_Lube_Dropper_Silicone_Oil_50_oz/3002

P11 of the Ruger Manual specifically calls for RWS Lube and Crosman Nitro's use silicon oil for the air chamber as well.

Thurmond

I would only use the silicone if your gun 'honks' while cocking it-that would indicate a dry piston seal. If it's "twangy" that's the mainspring and guide. If you feel you need the silicone lube, use only a few drops, and work the barrel back and forth while turning the gun to help distribute the lube-use sparingly!

Just spend the 7$ for the RMC oil. It is what the nitro piston manual calls for 

I wouldn't base a opinion off of the inter web as much as I would from the manual. 

I searched all over looking for RMC oil or similar silicone chamber oil in my town. Dicks, Walmart and big5 never heard of it. Ended up going on Walmart.com and ordering it for 7.99$.
From what the manual says usually one drop every couple hundred shots is best. I've shot about 400 rounds and still haven't used any. Just my preference to insure a nice break in period before using oil. I plan on putting one drop down the chamber in the next hundred rounds. 

I shoot a Benjamin Regal II NP .22

Still new to the modern air guns that we have today and I must admit. The quality is superior to what I remember as a child. Could be my marksmanship is better now and I pay more attention to the quality of the rifles.
Hope this helps.