Thank you all for the advice. My intent is to "shore up" the gun so it doens't get any looser. I must ask, however, where to I place the shim(s)? Are they placed on the barrel hook or on the action pin? I know this seems like a pretty simple question, but I am very new at any repairs involving the metal rather than the wood.
I see that many others end their posts with a phrase that means a lot to them. Here is mine:

Perfect is the enemy of good.
Mike