I believe thye G grade was not introduced until the two hook guns were put on the market in 1890. I would suspect that most of the 2 5/8" chambers preceded that.
When you say "Looseness in the Lockup" are you speaking of bolting or the hinge. If in the bolting the wedge shape of the bolt is to compensate for this wear with the top lever going left. If the lever is all the way left & it is still loose in the bolting it will need a new bolt made.
"Do Not" try to compensate for bolt wear with the ball joint, it is strictly for compensating for hinge wear.
