DT:

It's how the relationship between the moving parts are "timed" during the opening and closing of the action, and it effects just about everything - retraction of the firing pins, ejection, "springback", etc. For example, on a "best" gun, the ejectors will kick and the sears pop into place just as the barrels reach the bottom of their downward movement, and there's no "springback". Good quality double guns are well timed, "best" guns are perfectly timed, in addition to having best quality finish.

With several of the Searcy's I've handled lately, as the gun was opened, the top lever moved out to the right, but then back almost to center as the barrels reached bottom, instead of staying right. Further inspection confirmed that the bolts did not remain retracted as they should. Then, as the gun was rotated shut, there was a significant hitch as the barrel lugs struck the unretracted bolts, having to force them back against their spring so that the gun could close. This would be unacceptable on a double gun that costs a quarter as much.
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