Hey Todd, if you don't have any tar on hand, you might try a sticky type grease like 5th wheel grease. Not the best, but it's worked for me in the past, and I'd save the moly for other uses. Your numbers sound a little low for the rm. How does the seal look? I'd like to see some pix of the rifle broken down. Have you measured the spring to see if Macarri has one that will work? Your spring may be 'spent'. About the seal size, it all depends, but if you clean it up and moly the piston around the seal and rear end of it, you will never need to "oil" the rifle which maybe why the piston is hard to get out of the action. JMO, oil is a poor type of lubricant for spring guns,...grease and moly is much better. Hope this was some help, tjk
PS post some pix!!