I'd like to hear more about how you fit a modern breech bolt to your old 39. I'll be taking possession of a 20s model 39 soon and may decide to do the same. Where did you get the modern breech bolt and what did you have to do to make it work in the old gun?
=*j-w-m*;3083785]Everything functions in my Marlin Model 39 lever action circa 1920s; but I had to fit a modern breech bolt to handle the hi-vel ammo.The S-prefix serial number 39 breech bolts were only able to handle standard velocity stuff.
I discussed it on another forum:
There is a slim chance it may fit fine without any work!
Smoke it with a Zippo as needed to reveal where it needs fitting, making sure you only file the new bolt, not the receiver!
Some reshaping of the firing pin was needed as well.
You just have to go slowly and think about it, testing the fit frequently.
Pretty easy, but tedious for an hour or two.
Try you old pin; it may work or you can use it as a basic pattern.
The new style extractor
Firing pin that may need a little filing to make it flush in the new bolt: