A theft or loss of firearms must be reported to your local police as well as to ATF within 48 hours after the discovery. Licensees should notify ATF on the 24-hour, 7 days a week toll free line at 1-800-800-3855 and by preparing and submitting ATF Form 3310.11, Federal Firearms Licensee Theft/Loss Report.
Theft or loss of NFA firearms should also be reported to the NFA Branch immediately upon discovery.
[18 U.S.C. 923(g)(6), 27 CFR 478.39 and 479.141]