27 C.F.R. § 53.61 : Alcohol, Tobacco Products and Firearms — ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY — FIREARMS — MANUFACTURERS EXCISE TAXES-FIREARMS AND AMMUNITION — TAX RATES — Imposition and rates of tax

(a) Imposition of tax. Section 4181 of the Code imposes a tax on the sale of the following articles by the manufacturer, producer, or importer thereof:
(1) Pistols;
(2) Revolvers;
(3) Firearms (other than pistols and revolvers); and
(4) Shells and cartridges.
(b) Parts or accessories -
(1) In general. No tax is imposed by section 4181 of the Code on the sale of parts or accessories of firearms, pistols, revolvers, shells, and cartridges when sold separately or when sold with a complete firearm for use as spare parts or accessories. The tax does attach, however, to sales of completed firearms, pistols, revolvers, shells, and cartridges, and to sale of such articles that, although in knockdown condition, are complete as to all component parts.
(2) Component parts. Component parts are items that would ordinarily be attached to a firearm during use and, in the ordinary course of trade, are packaged with the firearm at the time of sale by the manufacturer or importer. All component parts for firearms are includible in the price for which the article is sold.
(3) Nontaxable parts. Parts sold with firearms that duplicate component parts that are not includible in the price for which the article is sold.
(4) Nontaxable accessories. Items that are not designed to be attached to a firearm during use or that are not, in the ordinary course of trade, provided with the firearm at the time of the sale by the manufacturer or importer are not includible in the price for which the article is sold.
(5) Examples -
(i) In general. The following examples are provided as guidelines and are not meant to be all inclusive.
(ii) Component parts. Component parts include items such as a frame or receiver, breech mechanism, trigger mechanism, barrel, buttstock, forestock, handguard, grips, buttplate, fore end cap, trigger guard, sight or set of sights (iron or optical), sight mount or set of sight mounts, a choke, a flash hider, a muzzle brake, a magazine, a set of sling swivels, and/or an attachable ramrod for muzzle loading firearms when provided by the manufacturer or importer for use with the firearm in the ordinary course of commercial trade. Component parts also include any part provided with the firearm that would affect the tax status of the firearm, such as an attachable shoulder stock.
(iii) Nontaxable parts. Nontaxable parts include items such as extra barrels, extra sights, optical sights and mounts (in addition to iron sights), spare magazines, spare cylinders, extra choke tubes, and spare pins.
(iv) Nontaxable accessories. Nontaxable accessories include items such as cleaning equipment, slings, slip on recoil pads (in addition to standard buttplate), tools, gun cases for storage or transportation, separate items such as knives, belt buckles, or medallions. Nontaxable accessories also include optional items purchased by the customer at the time of retail sale that do not change the tax classification of the firearm, such as telescopic sights and mounts, recoil pads, slings, sling swivels, chokes, and flash hiders/muzzle brakes of a type not provided by the manufacturer or importer of the firearm in the ordinary course of commercial trade.
(c) Rates of tax. Tax is imposed on the sale of the articles specified in section 4181 of the Code at the rates indicated below.

Percent
(1) Pistols 10
(2) Revolvers 10
(3) Firearms (other than pistols and revolvers) 11
(4) Shells and cartridges 11

(d) Computation of tax. The tax is computed by applying to the price for which the article is sold the applicable rate. For definition of the term "price" see section 4216 of the Code and the regulations contained in subpart J of this part.
(e) Liability for tax. The tax imposed by section 4181 of the Code is payable by the manufacturer, producer, or importer making the sale.

27 C.F.R. § 53.61

T.D. ATF-308, 56 FR 303, 1/3/1991, as amended by T.D. ATF-404, 63 FR 52603, 10/1/1998