I just purchased a Model 1 Sales action block / insert for working on uppers. My question is how snug does the action block have to fit the upper to prevent damage? I used a different brand that belongs to one of my buddies the last time I swapped barrels, and it was a very snug fit, with no play. I just stuck the Model 1 Sales action block on two ifferent uppers and there is quite a bit of play between the upper and the block. Any one with experience using the Model 1 Sales action blocks? Good? Bad? indifferent? Thanks in advance.

I have the action block from Brownells and there isn't any play.  

+1 on the Brownells.  Rock solid.