Due to US Bureau of Alcohol, Tobacco, Firearms and Explosives regulations, members and/or guests are prohibited from working on any firearm while on Twin Cities Maker property.
BATFE ruling 2015-1 states:
[…] a business (including an association or society) may not avoid the manufacturing license, marking, and recordkeeping requirements of the GCA [Gun Control Act of 1968] by allowing persons to perform manufacturing processes on blanks or incomplete firearms (including frames or receivers) using machinery, tools, or equipment under its dominion and control where that business controls access to, and use of, such machinery, tools, or equipment.
For the purposes of this policy, “firearm” is defined as in 18 U.S.C 921(a)(3) and (4):
(3) The term “firearm” means
(A) any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive;
(B) the frame or receiver of any such weapon;
(C) any firearm muffler or firearm silencer; or
(D) any destructive device.
Such term does not include an antique firearm.
(4) The term “destructive device” means—
(A) any explosive, incendiary, or poison gas—
(iii) rocket having a propellant charge of more than four ounces,
(iv) missile having an explosive or incendiary charge of more than one-quarter ounce,
(v) mine, or
(vi) device similar to any of the devices described in the preceding clauses;
(B) any type of weapon (other than a shotgun or a shotgun shell which the Attorney General finds is generally recognized as particularly suitable for sporting purposes) by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, and which has any barrel with a bore of more than one-half inch in diameter; and
(C) any combination of parts either designed or intended for use in converting any device into any destructive device described in subparagraph (A) or (B) and from which a destructive device may be readily assembled.
The term “destructive device” shall not include any device which is neither designed nor redesigned for use as a weapon; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic, line throwing, safety, or similar device; surplus ordnance sold, loaned, or given by the Secretary of the Army pursuant to the provisions of section 4684(2), 4685, or 4686 of title 10; or any other device which the Attorney General finds is not likely to be used as a weapon, is an antique, or is a rifle which the owner intends to use solely for sporting, recreational or cultural purposes.
[https://www.atf.gov/firearms/docs/ruling/2015-1-manufacturing-and-gunsmithing/download BATFE Ruling 2015-1]
[https://www.gpo.gov/fdsys/pkg/USCODE-2011-title18/html/USCODE-2011-title18-partI-chap44-sec921.htm United States Code, 2011 Edition] Title 18 - CRIMES AND CRIMINAL PROCEDURE PART I - CRIMES CHAPTER 44 - FIREARMS Sec. 921 - Definitions