Funny how you experience things yourself and then almost immediately you read a post that you can/could have used. Two posts on this page, the one about the scope bases and the one about having difficulties matching barres to a G2 frame are examples.
I had purchased some bases, both or my Encore and G2. I hadn't used one of the bases and since it was aluminum I decided to put it on my .22 l.r. barrel (to keep weight down). When I began screwing the based down I noticed that the screws were beginning to bottom out before the base was snug to the barrel. I ended up snapping one head off of one of the screws in the process. Thankfully it broke off at the head and I was able to remove the remainer with pliers. After installing the based I remember thinking that it really wasn't sitting flush. About five minutes later I realized that it might be an encore base. I confirmed my suspicion with the package in the trash. So, Encore bases don't go on G2s or Contenders.