Compared to my all stainless steel M-60, the 642-2 is a featherweight! Often times, it rides comfortably in my pocket without me noticing the bulk or the weight.
When firing heavier cartridges, you will notice the difference in recoil!
You won't regret the purchase!
I also have a DeSantis Nemesis holster that I carry mine in for even lighter weight. At less than $20.00, they are a bargain. Armed with the revolver and Bianchi Speed Strips for reloading, you have a very concealable and effective carry package!
The 642-- what a great gun. The lock has not presented a problem on any of my Smiths, heavy recoil or not. I carry the 642 almost every day and practice with it frequently. I think you will enjoy your new purchase.
The 642 does have an unusual coating on the frame that wears quickly. I finally had mine bead blasted and sprayed with a dark green duracoat. It looks better, some may disagree, and the coating is more durable than the original.
I have several Smiths with locks, including a 625 Mountain Gun in .45 Colt, a 625 full lug Model of 1989 in .45 ACP, and the M638 in my pocket, which of the three is most similar to your 642. I've had exactly ONE "issue" with the lock, and it was my fault anyway, so I won't go into the explanation. The 638 has fired umpteen hundreds of rounds without a hitch.