27 CFR 478.126a:
http://ecfr.gpoaccess.gov/cgi/t/tex...iv8&view=text&node=27:3.0.1.2.3.8.1.9&idno=27
§ 478.126a Reporting multiple sales or other disposition of pistols and revolvers.
Each licensee shall prepare a report of multiple sales or other disposition whenever the licensee sells or otherwise disposes of, at one time or during any five consecutive business days, two or more pistols, or revolvers, or any combination of pistols and revolvers totaling two or more, to an unlicensed person: Provided, That a report need not be made where pistols or revolvers, or any combination thereof, are returned to the same person from whom they were received. The report shall be prepared on Form 3310.4, Report of Multiple Sale or Other Disposition of Pistols and Revolvers. Not later than the close of business on the day that the multiple sale or other disposition occurs, the licensee shall forward two copies of Form 3310.4 to the ATF office specified thereon and one copy to the State police or to the local law enforcement agency in which the sale or other disposition took place. Where the State or local law enforcement officials have notified the licensee that a particular official has been designated to receive Forms 3310.4, the licensee shall forward such forms to that designated official. The licensee shall retain one copy of Form 3310.4 and attach it to the firearms transaction record, Form 4473, executed upon delivery of the pistols or revolvers.
Example. 1. A licensee sells a pistol and revolver in a single transaction to an unlicensed person. This is a multiple sale and must be reported not later than the close of business on the date of the transaction.
Example. 2. A licensee sells a pistol on Monday and sells a revolver on the following Friday to the same unlicensed person. This is a multiple sale and must be reported not later than the close of business on Friday. If the licensee sells the same unlicensed person another pistol or revolver on the following Monday, this would constitute an additional multiple sale and must also be reported.
Example 3. A licensee maintaining business hours on Monday through Saturday sells a revolver to an unlicensed person on Monday and sells another revolver to the same person on the following Saturday. This does not constitute a multiple sale and need not be reported since the sales did not occur during five consecutive business days.
