S&W found that the pinned barrels didn't really need to be pinned to stay tight.
So, they got rid of them in new production.
Both styles, regardless of pinned or not, need a crush fit.
Different smiths will have different opinions, but most advocate between a 1/8 to 1/4 turn crush fit.
That means the barrel is turned on by hand until tight, and then with the appropriate tools the barrel is tightened a further 1/8 to 1/4 turn.
The goal of course is to have the barrel rib at Top-Dead-Center after the final tightening.
So, what you do is put the barrel on by hand and see where it stops. If it is greater than a quarter turn from T.D.C. you will remove it and shave some steel from the face of the barrel (only shave a very small amount at a time, <.001").
You then repeat the process until the barrel can be hand-tightened to between 1/8 and 1/4 turn from TDC, then tighten with the right tools.
Once the barrel is on the barrel to cylinder gap will be set by cutting the excess barrel shank away.
After that the forcing cone is recut and the job is done.
This can be done at home be the amateur, but you will have to buy the forcing cone tools and B/C gap tools, and you will need to have the right set-up to tighten the barrel without bending the frame.
So, it really is best to send a gun to S&W or other competent pistolsmith for rebarreling.
Odds are the results will be much better and the labor cost will probably be less (than if you bought your own tools).
FWIW, -Kframe
