I have located a SS J frame 22lr cylinder for sale and would like to know if it would have to be fitted or would it just drop in on a 651 no dash? I have read that when the 651 first came out you could order an extra 22lr cylinder with it. Advice appreciated.

Others are more experienced in this realm than I,but I'll say "either/or" ;-)
You may get lucky with a drop in,you may need fitting.

It may be better odds than winning the mega lottery if it is a drop in, but my guess is it will need fitting, and then, it may not fit at all.

Hope this helps
chris

The odds of it being a "drop-in" fit are strictly a crapshoot.

With similar revolvers made in a given era (+/- 10 years) a usable fit happens about one out of four times. Maybe not even that.

Just think about what needs to be within specification to be a "drop-in fit:" barrel-to-cylinder gap, headspace, endshake, ratchet-to-hand fit, proper carry-up, extractor rod-to-locking bolt fit, center pin-to-locking bolt fit, and action timing.

At S&W, the spare cylinder was fitted. In your case, a cylinder of undetermined origin may have already been fitted to another frame and be outside of the tolerances to even allow fitting to your gun.

I guess I'm just not as pessimistic as most based on my experiences with Smiths. I even exchanged a 6 shot cylinder with a 5 shot cylinder of different caliber in a gun 20 years different in vintage that worked perfectly well within tolerances. Didn't even have to change the hand!

Even if you have to take it to a gunsmith for a little fitting. Or worse case scenario, you can resell it.
Or you can send the gun back to S&W to have a new 22 LR cylinder installed. That price might give you some incentive to give the used cylinder a try.

Let us know what you decided to do.

All the best,

__________________
Jim
S&WCA #819