I have a marlin 336 in 30/30 and have come across a barrel for it that is 22" long and has some nice touches to it. I know that there is quite a bit of machining necessary to make a barrel fit a bolt action so the headspace is just right, but what about a lever action. Would I be making an error if I pull hte old barrel off and put the new one on and then use headspace gauges to check my amateur gunsmithing? Any and all help would be appreciated, especially if someone can lend me some insight on how a lever action is headspaced, etc. By the way, the caliber is remaining the same. Thanks in advance.

Marcus---

Unless they've changed lately the 336s aren't "indexed" as to where the reciever threads start. That means every barrel is fitted and THEN the extractor cuts are made.

Unless you have a lathe and a reamer and are pretty good with a file for deepening the extractor slots and have a headspace gauge.....you're better off leaving it alone.

BTW--Some 336 Marlins have V threads and others have square.

JBelk is right, but a perfectionist. I would not mess with it if the current barrel is good.

However, being an incorrigble tinkerer, if I had a Marlin with a junk barrel, I would use a headspace gauge and shim stock to establish just what the current headspace is. Then, I would pull the barrel and measure one against the other, assuming that you have been talking about another Marlin barrel, likely a takeoff. If things looked workable, I would screw the replacement home and see what I had. If the extractor cut matched, and the headspace was not over .005 over the no go gauge, I'd call it good enough. At worst, you would wind up taking it back off.

All this supposes that you have the tools and some practice at changing barrels. And I am also predicating this on a cheapie rifle with a moderate cartidge. In this one case, "good enough" would be good enough.