What is the test for reducing the crime level of possession of a firearm under section 2K2.2(b)(3) of the Guidelines de novo?

We review the district court's findings of fact for clear error, and its application of the Guidelines de novo. United States v. Howard, 894 F.2d 1085, 1087 (9th Cir.1990). The defendant has the burden of proving by a preponderance of the evidence that he is entitled to a reduction in offense levels. Id., 894 F.2d at 1090. At the time of sentencing, section 2K2.2(b)(3) provided in pertinent part, "[i]f the defendant obtained or possessed the firearm solely for sport, recreation or collection, decrease [the offense level] by six levels."