The interface between the front locking bolt and the end of the extractor rod serves to mitigate that movement, and support the assembly during firing. Some gauge between the parts is essential however, for the cylinder assembly to rotate without interference. This is one reason why reducing run out on the extractor rod is so important, as run out can cause the cylinder to intermittently bind on the f.l. lug)

Excessive movement, if present, may be due to the front locking bolt/extractor rod end being worn, or the parts may not have been fit properly in the first place.

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Ret. LE, FA Instr, S&W Armorer