I need a hammer spur and scope mount plate for marlin 336 lever 30-30

try manufacturer site or gun shop for specs

Norman contact Marlin/Remington through there customer support/help center to order spur/hammer extension.
Check the attached links, Good luck
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Uncle Mike Hammer Extension Marlin Lever Action Post 1983 Blue

The letters JM stamped on the barrel are the Marlin Firearms Co. factory mark. John M. Marlin was the founder of the company.

Probably the ejector itself, or the extractor.

You weren't too specific.

Is the round staying in the chamber?
Coming part way out?
Coming all the way out, just not ejecting out the action?
Coming out, and staying in full contact with bolt face?
Coming out, dropping away from bolt face?
Etc..........

The Model 336 series has been made since 1948.
Early rifle serial number are located on bottom tang under the lever.
Later the serial number was moed to the top tang behind the hammer.
There should be one or two LETTERS in front of the serial number, that determines the year.
If there is no letter then it was made after 1969.

TRY THIS LINK
http://www.gunvaluesboard.com/marlin-serial-numbers-dates-of-manufacture-1664.html

TRY THIS LINK
http://www.gunvaluesboard.com/marlin-serial-numbers-dates-of-manufacture-1664.html

1870 was when Marlin Firearms Company was established.

Need a serial number for age of a particular rifle.