See related link below
A guy on eBay has a store called Rediscovered Shooting Treasures (RST). He sells reproductions of the Marlin Model 120 manual.
Brophy's book on Marlin Firearms history would be the place to start. I own a model 995, have a copy of the manual.
Look for a manual for a Marlin 60. e-gunpats.com may sell them. Updated Answer - You can also download a free manual on the Marlin web site for the model 60 - it is the same firearm. http://www.marlinfirearms.com/Firearms/SelfLoading/60.asp
I THINK you have a Marlin Model 60, made for JC Penney as their Mdel 6660. You can download an owner's manual from Marlin, customer service, use the Model 60 tab. You can also check the website at gunpartscorp, again use marlin Model 60.
Marlin 336 Owners Manual at Marlin Firearms website: http://www.marlinfirearms.com/pdfs/manuals/MFC_Centerfire.pdf
Visit the Marlin website. They may have the owner's manual available for download. If not, they will supply you a paper copy, typically free of charge.
If you don't have an owner's manual, find a gunsmith. You can try gun shows and want ads to find a manual as well as internet searches. Good luck.
Visit the Numrich Marlin/Glenfield page. Or the Marlin home page to download the PDF version of the Model 60 manual. These two rifles are very similar in design. http://www.gunpartscorp.com/catalog/Models.aspx?catid=310 Marlin downloads. http://www.marlinfirearms.com/customersupport/manuals.asp
The Marlin Glenfield model 20 is the same basic gun as a Marlin model 780. Contact Marlin direct at: Marlin Services P.O. Box 248 North Haven, CT 06473 They will send you a free manual for the 780. Or you can call them toll free at: 1 (800) 544-8892 I am not aware of any web sites that offer this manual as a download. For free downloadable manuals of a lot of other firearms try here: http://www.again.net/~steve/page7b.htm Regards, Rob
Contact Marlin.
I, too, have been trying to find out about the Marlin 30-30 Model 30AW and I discovered that the Model 30AW is the low priced version of the Model 336. (Very disappointing to pay $400 for a gun to find out it is a "low priced version".) Anyway, here is a link to the owners manual I found: http://www.marlinfirearms.com/pdfs/manuals/MFC_Centerfire.pdf It appears to be the same gun that I purchased.
A statement of fact? If this is another question just type it into google.