Extractor cams modification?

[Geezer7]

Dear S&W Gunsmith

I am fitting a model 648 cylinder to my pre-model 17.

I bought all new 648 parts--cylinder, extractor, extr rod, extr rod collar, extr spring, center pin, and center pin spring--so I could just swap the yoke between LR and Mag cylinder assemblies.

I had to shorten the center pin to make the 648 assembly close into battery, but no other mods seemed necessary.

However, the 648 assembly will cycle on only 4 of 6 positions, binding in always the same 2 of 6 positions.

Please see the attached pics to see how differently shaped the extractor star cams are on the the model 648 vs. the model 17.

My assumption--I'm lucky 4 of 6 positions work, but should file all the m648 cams to shape them all as close as possible to the m17 cams.

Unfortunately because of the close cylinder/recoil shield gap, I can't see the hand mating to the cams, and don't want to ruin the new m648 extractor star cams by filing them wrongly.

Can you please advise?

Thanks in advance,
Bruce

 

[Protocall_Design]

No need to reshape all the ratchets (cams). There were several variations over time, but they all work. Only work on the 2 ratchets that don't work. Don't change the working ones.

With the sideplate off, and hammer and mainspring out, you can cycle the action and watch how the hand and ratchets interact through the back of the hand window.

 

[Geezer7]

Hallelujah! Your advice worked perfectly, and now so does my .22 Mag conversion cylinder.

Thanks SO much!!!

 

[Protocall_Design]

Dang! Got lucky again!