Jakk280rem said: "the only caveat i have to add to the above posts is to not use non jacketed ammo. factory 38 spcl lead loads have a very light crimp so as not to deform the bullet during assembly. the low mass of the gun can cause the bullets to become unseated during recoil, binding the cylinder. stick to jacketed or hardcast bullets with a firm crimp, and enjoy."
That is true of S&W Airlite snubbies, the frames of which contain woofle dust to get them as light as possible yet still hold their shape in a high wind. But the 642 is an Airweight, not an Airlite. I fire almost nothing BUT lead from my 637 Airweight (the 642 clone with the visible hammer), so far about three thousand of them. Every other week I shoot fifty rounds of standard pressure 148gr WCs at the range. Even with that wimpy load, that is all my hand will take. Often I will also fire a load of my HD/SD ammo, Remington +p 158gr LSWCHPs -- the FBI load. Five of those is quite enough for practice, thank you very much indeed.
The only lockups I have had were at first when I forgot to tighten the ejector handle. I don't forget anymore, so I decided to skip the Locktite route.
Cordially, Jack