I recently acquired a new Model 18, one of S&W's Classics series revolvers. It is a nice addition to my previously acquired Model 19, Model 67, and Model 642. The "dash" number on my new Model 18 is "-7". Just what was the engineering change that S&W made to this version? I have information about the engineering changes associated with the -1, -2, -3, and -4 versions, but not for the -5, -6, or -7. I suspect one involved the inclusion of the key lock feature. Another may have involved using the crush fit barrel rather than the pinned barrel. Any help in understanding these most recent changes would be appreciated.

According too the SCS&W III, the Model 18-4 lost the barrel pin in 1977 but there was no "dash" change to mark this. The barrel fitting technique actually didn't change much when the pin was dropped, the pin was largely cosmetic anyway.

The Model 18 designation was dropped completely in 1985 and it was replaced by the Model 17-4 getting a 4 inch barrel option.

No mention in the book of the 18-5, 18-6 or 18-7 variants.

What were the missing variants? Good question!

The pinned barrel lasted until about 1982. It was not a dash numbered engineering change.
The 18 was dropped from 1985 in favor of a 4" 17. That is most likely where the lost dash numbers are. The "classic" picked up at -7.

Thanks to all for the replies. I had also looked in SCS&W III and couldn't find anything regarding the -5, -6, or the -7 (of course the book was published in 2006, so I didn't expect to find anything more recent in its pages).

Just compared my 18-3 to my 18-4,
Besides not having the barrel pin I just noticed the top of the frame ( just ahead of the rear site ramp) is not machined to match the grooves cut into the barrel ramp ....will take pics later.
Anybody else have an 18-4 with this missing feature?

It is common to most target-sighted S&W's made after they also dropped the P/R features. On the older guns, the frame was grooved from under the rear sight body, the sight body was grooved and the barrel's top rib was grooved, all the same way. It looks nice, uninterrupted grooving. P/R was dropped to save some machining steps and their costs, and I guess the lack of grooving on the frame's topstrap was just that much more machine time eliminated.

I thought this was kind of tacky. Although it is just cosmetic, I am surprised more people haven't noticed it.