Matter of PF, 20 I. & N. Dec. 661 (BIA 1993) ("In the absence of any evidentiary showing by the respondent that the weapon was an antique firearm, we find that the conviction record establishes that the respondent used a "firearm," as defined by 18 U.S.C. 921(a) (1988), in the commission of the armed robbery. See United States v. Laroche, 723 F.2d 1541 (11th Cir.), cert. denied, 467 U.S. 1245 (1984).").