Absolutely!
§122.1 Registration requirements.
(a) Any person who engages in the United States in the business of manufacturing or exporting or temporarily importing defense articles, or furnishing defense services, is required to register with the Directorate of Defense Trade Controls under §122.2. For the purpose of this subchapter, engaging in such a business requires only one occasion of manufacturing or exporting or temporarily importing a defense article or furnishing a defense service.
A manufacturer who does not engage in exporting must nevertheless register.
This does not apply to just metalwork, it applies to anything covered in the munitions list.
http://www.pmddtc.state.gov/regulations_laws/documents/official_itar/ITAR_Part_121.pdf
Take a look at page 2 CATEGORY I—FIREARMS, CLOSE ASSAULT WEAPONS AND COMBAT SHOTGUNS. Also take a look at section (h) Components, parts, accessories and attachments for the articles in paragraphs (a) through (g) of this category. It looks to me like it says if you are engaged in the business of making anything for a firearm you are subject to ITAR.
This can include stocks. Are you in the business of making stocks for sale? You are subject to ITAR. A well known chassis maker has stated he was convinced by the govt that he should register.