Did S&W beef up the mainspring between mid 80's and later?

[DHart]

I recently acquired as S&W Model 65-5 and I've found that the stock mainspring in this 65 is slightly heavier than the mainspring S&W used when they built my Model 66 in the mid eighties.

Swapping the spring from the mid-eighties Model 66 into my newly acquired 65-5 gives the 65 a dramatically improved trigger pull. But to the naked eye, the two springs appear identical. A micrometer reveals that the spring from the mid-eighties 66 is just a tad thinner than the mainspring in the 65-5, which must have been built quite a bit later than the mid eighties.

I wonder if S&W went to the slightly thicker mainspring during the later years for legal reasons. Or perhaps suppliers changed and the specs varied just a bit. Anyone have any idea?

 

[Trebor]

Try asking at the Smith and Wesson forum. www.smith-wessonforum.com

I bet someone there will know the answer.

 

[Jim March]

If the later gun uses a transfer bar ignition and the older has a firing-pin-on-hammer setup (with the "hammer block" safety), that will explain it.

Transfer bar ignitions have more "pieces" between the hammer and the primer - there's the transfer bar itself and the frame-mounted firing pin. This causes energy losses. The mainspring needs to be up to 25% stronger on a tranfer-bar gun to get the same ignition reliability.

 

[MoNsTeR]

Anecdotal at best, but the mainspring in my 686-3 is noticeably heavier than the one in my dad's 686 no dash.

 

[DHart]

Both of the S&W's I'm comparing have hammer mounted firing pins. Simply swapping the mainspring from the 66-3 to the 65-5 instantly transformed one revolver to a stiffy and the other to a smooth, slick action, where they each were the opposite before the switch. I'll post this on the S-W forum. Thanks for the notes.

 

[Old Fuff]

Both of the S&W's I'm comparing have hammer mounted firing pins. Simply swapping the mainspring from the 66-3 to the 65-5 instantly transformed one revolver to a stiffy and the other to a smooth, slick action, where they each were the opposite before the switch. I'll post this on the S-W forum. Thanks for the notes.

I learned a long time ago that the springs aren't different, but sometimes the temper is. This can make a difference in the way they feel.

Also when you are experimenting between two guns of the same kind, switch the mainspring strain screws also. Sometimes they very in length, and this can also make a difference.

 

[RON in PA]

Jim March: since when did Smith& wesson ever use a transfer bar system? They have frame mounted firing pins in some models (all current production), but no transfer bars. Try Ruger and later model Colts.

 

[DHart]

Here's the new thread over on the S-W forum:

http://www.smith-wessonforum.com/ubb/Forum13/HTML/016432.html