Google told me that this problem is not uncommon among high powered springers. A few solutions which cropped up were, to use a truckload of adhesive, a weaver rail, a 1-piece mount or a scope stop ( http://www.gamousa.com/product.aspx?productID=107 ) . Since,these were not easily available in my area i went and bought an extra set of 3/8' dovetail rings.
So i screwed two rings each, forward and backward i.e. a total of 4 mounts grouped in two's. This seemed to solve the problem and after 25 shots the scope still seems to hold its place which is good XD .
Here are the links to the problem posted by users on other forums -
http://forum.bodybuilding.com/showthrea ... =112298041
https://answers.yahoo.com/question/inde ... 405AA0VhN3
http://www.gatewaytoairguns.org/GTA/ind ... pic=2694.0
Hope this helps

EDIT: Purchased a one piece mount with a Vertical stop pin . The vertical stop pin is really important to prevent creep. A hole has been provided on the SX/NX series for the very same on the receiver.