Marlin 39- how to tell if bolt has been replaced

[Whynotthinkwhynot]

I just bought a Marlin 39, SN S14220, which by my current research is about 1937 or so before the HS. The previous owner took very good care of the firearm, so except for scratches on some of the wood it looks great. Unfortunately, it was an estate sale gun, so I don’t have much information on it’s history. Of course I’m concerned about breaking the original bolt with modern ammunition. That brings me to the question- How can I tell if the original owner replaced the bolt?

Being unfamiliar with these older Marlins, I originally assumed that the bolt had been replaced because of the bluing on the bolt contrasting the case hardened receiver. Further research shows that might not be a sign. Surely there must be some other way to tell. Although the condition of this firearm is good, it does appear that the previous owner used it extensively. About the only part that I can tell at this time which is “bad” is the forearm which has plenty of scratches from a rest or barb wire fence, or whatever it was that he continuously leaned the gun against, maybe there was a screw sticking up on his truck rack.

I fully intend on shooting the gun, but I’d like to be able to tell if I need to be wary of what ammunition I use.

[marlinman93]

Tough to describe the difference between the improved HS bolt and the previous bolts. But if you find a copy of Bill Brophy's book on Marlin Firearms history it has pictures of both side by side. They made the cut for the lever intersection smaller to reduce metal that was removed on earlier bolts. This increased the strength a lot.
But if you're in doubt, simply buy standard velocity modern ammo. It's perfectly safe in the old bolt, and wont harm it. I use Aguila super extra standard velocity in mine. It's very cheap at Cabelas at $2.99 a box, or $24.99 per 500 rd. brick, or 10 boxes.

[Whynotthinkwhynot]

Thanks for the answer! It was a long shot. I have a friend who owns a 39M, and I can probably convince him to let me compare the bolts side by side. I will provide pics when I can. I bought from an individual on GB, but the Post Office has decided to lose the envelope with the money order in it apparently.