whats my m14 worth?

[JBS]

If you are in the U.S. a registered and legally papered M14 can bring from 23,000.00 to 30,000.00 depending on condition and maker.

IF you have a M14 in the U.S. without paper it is worth 10,000.00 out of your pocket plus a stay in Federal Prison up to 10 years. The weapon will be seized and destroyed more than likely unless the seizing agency request a government transfer to that agency by the court.

The National Firearms Act ("NFA"), 73rd Congress, Sess. 2, ch. 757, 48 Stat. 1236, enacted on 26 June 1934, currently codified as amended as 26 U.S.C. ch.53, is an Act of Congress that, in general, imposes a statutory excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The Act was passed shortly after the repeal of Prohibition. The NFA is also referred to as Title II of the Federal firearms laws. The Gun Control Act of 1968 ("GCA") is Title I.
All transfers of ownership of registered NFA firearms must be done through the federal NFA registry. The NFA also requires that transport of NFA firearms across state lines by the owner must be reported to the ATF.
Criminal penalties
Violations of the Act 1938 are punishable by up to 10 years in federal prison and forfeiture of all devices or firearms in violation, and the individual's right to own or possess firearms in the future. The Act provides for a penalty of $10,000 for certain violations.[6] A willful attempt to evade or defeat a tax imposed by the Act is a felony punishable by up to five years in prison and a $100,000 fine ($500,000 in the case of a corporation or trust), under the general tax evasion statute.[7] For an individual, the felony fine of $100,000 for tax evasion could be increased to $250,000.[8]

On top of all this if by serial number it is found that this rifle was liberated from the DOD one can probably expect charges of position of stolen military ordinance.