Not exactly a S&W revolver but:

[jmbrowning]

Ruger LCR 357 magnum getting very proficient taking it nice or twice a week putting through 50 hand load +p 38 sp. I have had my other carry gun blow up in my face XDs 45 double charged. Believe me it took a little while to get back on the horse. Now I'm anal man coming to reloads 3 scales 5 dies and lots of handling. This time a had the polar opposite of a hot load, a squib. I was doing quite well at the range hitting in the 8 ring from 25yds free hand. Then the PFFFT. Tried hammering it out with a plastic squib remover. No avail. I had a squib in the past, cowboy load 45lc led not jacketed . Much easier. To make a short story long: could it be crimp problem. Wet components. I do no less than 3to 4 checks. Was using 5.8 unique 125gr xtp. My wife said I should just buy ammo, I'm having too much trouble. I don't want that to be an option. BTW the spent brass looked burned in comparison. Cliff notes will e on sale next week

 

[VictorLouis]

I am quite impressed with the LCR series. Sorry to read of your squib. Sounds like you will need an honest .35-sized brass rod. You may be able to find such at Ace, or True Value. Or, try a hobby shop.

 

[Waywatcher]

Spent brass on a squib will often appear scorched; the load didn't accumulate enough pressure to make the brass seal to the chamber as normal.

Squibs are not a crimp issue. Wet powder could do it. Was there a bunch of spilled powder all in the gun when it had the squib? If there was little to no powder, it was most likely a light/absent charge. If the inside of the gun had 5.8 grains of unique spilled all up in it, it was a component issue. (Spill 5.8 grains of unique, and you'll know how much you should have seen. It looks like quite a lot of powder when it is all spilled and spread out.) My suspicion is a very light or absent load of powder.

The number of scales and dies is not important; your complete attention and precision is important. It's just about impossible to say where you are going wrong with your reloads; but something in your process is not right. I've never had a squib or a kaboom, but I've only reloaded maybe 5 or 6 thousand cartridges.