OAL is measured with the stock extended.
From:
frwebgate.access.gpo.gov/cgi-bin/multidb.cgi[Code of Federal Regulations]
[Title 27, Volume 1]
[Revised as of April 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 27CFR179]
[Page 1001-1004]
TITLE 27--ALCOHOL, TOBACCO PRODUCTS AND FIREARMS
CHAPTER I--BUREAU OF ALCOHOL, TOBACCO AND FIREARMS, DEPARTMENT OF THE
TREASURY
PART 179--MACHINE GUNS, DESTRUCTIVE DEVICES, AND CERTAIN OTHER FIREARMS--Table of Contents
Subpart B--Definitions
Sec. 179.11 Meaning of terms.
" ...Firearm. (a) A shotgun having a barrel or barrels of less than 18
inches in length; (b) a weapon made from a shotgun if such weapon as
modified has an overall length of less than 26 inches or a barrel or
barrels of less than 18 inches in length; (c) a rifle having a barrel or
barrels of less than 16 inches in length; (d) a weapon made from a rifle
if such weapon as modified has an overall length of less than 26 inches
or a barrel or barrels of less than 16 inches in length; (e) any other
weapon, as defined in this subpart; (f) a machine gun; (g) a muffler or
a silencer for any firearm whether or not such firearm is included
within this definition; and (h) a destructive device. The term shall not
include an antique firearm or any
[[Page 1003]]
device (other than a machine gun or destructive device) which, although
designed as a weapon, the Director finds by reason of the date of its
manufacture, value, design, and other characteristics is primarily a
collector's item and is not likely to be used as a weapon. For purposes
of this definition, the length of the barrel having an integral
chamber(s) on a shotgun or rifle shall be determined by measuring the
distance between the muzzle and the face of the bolt, breech, or breech
block when closed and when the shotgun or rifle is cocked.
The overall
length of a weapon made from a shotgun or rifle is the distance between
the extreme ends of the weapon measured along a line parallel to the
center line of the bore.