Alvin Scott Corey seeks to set aside his conviction for possessing a firearm as a felon, on the ground that the district court abused its discretion in admitting expert testimony that the gun Corey purchased had traveled in interstate commerce. We affirm.
I
BACKGROUND
In September 1997, an Easterfield model 916-A 12-gauge pump shotgun, manufactured by Smith and Wesson, was seized from Corey’s Maine residence by officers of the Somerset County Sheriffs Department. In due course, Corey, a convicted felon, was indicted for possessing a firearm which had traveled in interstate commerce. See 18 U.S.C. §§ 922(g), 924(e). At trial, the government called Agent Michael Coo-ney, a firearms enforcement officer with the Bureau of Alcohol, Tobacco, and Firearms (ATF), to establish that the shotgun had been manufactured outside of Maine, and hence necessarily traveled across state lines. Id. As Agent Cooney’s testimony is pivotal to the appeal, we describe it in detail.
A. The Direct Examination
After testifying on direct examination that he had been an ATF agent for six years,1 Agent Cooney described his official duties as “provid[ing] technical information *86regarding firearms identification, operation and design for purposes of assisting the [ATF] and the law enforcement community,” “testing] and evaluating] firearms submitted as evidence,” “handling] inquiries from industry and the general public regarding firearms,” and “assisting] in maintaining the ATF firearms reference collection of approximately 5000 firearms.” He had testified as an expert witness on approximately sixty-five occasions, regarding “the identification, interstate nexus, operation and design of firearms.”
The defense nonetheless objected to Agent Cooney’s expert qualifications on the “interstate nexus” element of 18 U.S.C. § 922(g). The district court overruled the objection.
After Agent Cooney confirmed that he had examined the Corey shotgun, the government requested “a brief description of [the gun], including the weapon type, markings, and its history.” Cooney then identified the shotgun as “a Smith and Wesson, Model 916-A, twelve-gauge, pump-action shot gun, serial number 7B1279,” which had been “manufactured by the Smith and Wesson firearms company of Springfield, Massachusetts.”2 The defense asserted foundation and hearsay objections as soon as the prosecutor asked Cooney whether, “[b]ased on [his] examination of the weapon and [his] research,” he had formed an opinion as to the place of manufacture. At that point the district court permitted the defense to voir dire the witness.
B. The Voir Dire by the Defense
On voir dire, Agent Cooney testified to possessing “substantial expertise in identifying firearms,” having handled “hundreds of thousands of firearms” and examined Smith and Wesson shotguns of the type owned by Corey. Cooney stated that the principal Smith and Wesson manufac-tuning plant is situated in Massachusetts, but that other Smith and Wesson plants are located in Ohio and Maine. He stated that he had been able to determine from ATF “technical references” and “technical manuals” that the Corey shotgun was manufactured at the Smith and Wesson plant in Massachusetts. Further, he testified to having spoken with Smith and Wesson personnel at the Massachusetts plant about the Corey shotgun. Finally, when asked whether ATF reference manuals would indicate where particular firearms were manufactured, Agent Cooney responded that ATF possesses “in-house technical information ... provided us by the factory, and other information we keep in-house that I use for reference.”
After the defense invited him to identify the “items” he had relied upon in determining where the Corey shotgun had been manufactured, Cooney responded: “The Smith and Wesson history background file that we have on the company, and there is a notation in there about these shotguns, where they’re made.” Asked to explain how the ATF had compiled these files, and whether its files were comprised exclusively of information sent to the ATF by the manufacturers, Cooney explained that the files consisted of “information that we’ve had from speaking with the factory over the years, and in going there on tours and asking the Smith and Wesson historian, Mr. Roy Jinks, who’s written historical books on Smith and Wesson.” At that point, defense counsel stated: “So a lot of this is, basically, what people tell you, either the company tells you or the people at the company ... or records or memos you may get from the company.” (Emphasis added.) Cooney responded: “That’s correct”.
The defense renewed its objection, insisting that Cooney had relied “strictly [on] hearsay evidence that he gathers, people telling him where these things are *87manufactured.” The defense claimed that the perceived hearsay problem could be cured only by requiring the government “to generate the business records from these factories that show that [the shotgun] was or wasn’t manufactured there.” The government countered that Federal Rules of Evidence 702 and 703 permit an expert witness to formulate an opinion based on facts of a type reasonably relied upon by experts in the particular field, and that Agent Cooney had demonstrated that his methodology met that requirement.
The district court overruled the hearsay objection, on the ground that Cooney “ha[d] testified [that] he acquired this information over the years, has made studies and read a book by someone, and the history of Smith and Wesson, looked at notations that were made over the years as to where certain models come from.” The court then declared itself “satisfied that the reliability of [Agent Cooney’s] testimony is such that it’s admissible for the purpose for which it was intended, and it’s not based exclusively on hearsay that he obtained from a conversation with somebody else with regard to this weapon.”
C. The Direct Examination Continues
Agent Cooney testified that, in his opinion, the Corey shotgun had been manufactured by Smith and Wesson, either in Massachusetts or Ohio. Then he explained that he had attempted to rule out the Smith and Wesson plant located in Maine as the place of manufacture by phoning the Massachusetts plant on January 20, 1998, and speaking with Roy Jinks, the resident historian and the author of two books on Smith and Wesson. Jinks informed Coo-ney that the model shotgun owned by Corey had never been manufactured in Maine. Finally, Agent Cooney confirmed that he had based his expert opinion “on information that [Roy Jinks had] provided as well as the additional research.” (Emphasis added.)
D. The Cross-examination Resumes
The defense asked Agent Cooney whether the telephone conversation with Jinks “was the extent of what you did to determine whether this [shotgun] was manufactured in Maine or not ... ?” Coo-ney responded: “That was one of ... my procedures in my examinations of the shotgun, what I do with every type of weapon; I check the technical files, our research library, if necessary call the factory.” (Emphasis added.) When the defense asked whether he had telephoned Jinks because the technical files and research library had proven “inconclusive,” Agent Cooney responded: “No, sir. I always like to get two or three places to check my research.” In addition, Cooney reiterated that notations in the ATF files reflected that these shotguns were manufactured in Massachusetts between 1972 and 1981, and in Ohio between 1982 and 1984, at which time Smith and Wesson sold the line to a third party. Finally, Agent Cooney stated that he “called Smith and Wesson to verify that [these shotguns] had not been made in Houlton, Maine.” (Emphasis added.)
When the defense once again asked Agent Cooney to describe the various components of the ATF research files, he explained that it was “in-house generated information that we get from the factory, from brochures, from someone speaking with the factory prior to my calling them.” Finally, Cooney stated that ATF agents visit weapons factories, interview employees about new products, then include the updated information in the ATF files.
II
DISCUSSION
Citing exclusively to United States v. Trenkler, 61 F.3d 45, 57-61 (1st Cir.1995), and United States v. Davis, 571 F.2d 1354, 1356-58 (5th Cir.1978), Corey claims that the testimony given by Agent Cooney “was nothing more than his recollection of what others had told him,” thus constituted inadmissible hearsay.
*88We review rulings relating to the admissibility of expert-witness testimony for clear abuses of discretion, see General Elec. Co. v. Joiner, 522 U.S. 136, 141, 118 S.Ct. 512, 517, 139 L.Ed.2d 508 (1997), and will not reverse unless the ruling at issue was predicated on an incorrect legal standard or we reach a “definite and firm conviction that the court made a clear error of judgment.” United States v. Shay, 57 F.3d 126, 132 (1st Cir.1995); see United States v. Gresham, 118 F.3d 258, 266 (5th Cir.1997) (appellate review of rulings admitting ATF expert testimony on interstate nexus are “highly deferential”); United States v. Ware, 914 F.2d 997, 1002 (7th Cir.1990) (rulings admitting expert “nexus” testimony are reversed only if “manifestly erroneous”).3
Under section 922(g)(1), the United States must prove beyond a reasonable doubt that the defendant possessed a “firearm or ammunition which has been shipped or transported in interstate or foreign commerce.” 18 U.S.C. § 922(g)(1); see United States v. Bates, 77 F.3d 1101, 1104 (8th Cir.1996) (noting that the government need prove only that “there exists ‘the minimal nexus that the firearm[s] have been, at some time, in interstate com-meree’ ”) (emphasis added; citation omitted); United States v. Houser, 746 F.2d 55, 60 (D.C.Cir.1984) (same). Accordingly, the “interstate nexus” element was met provided the government demonstrated that Corey possessed the shotgun in a state other than the one in which it was manufactured. See United States v. Coleman, 22 F.3d 126, 130 (7th Cir.1994); United States v. Gourley, 835 F.2d 249, 251 (10th Cir.1987).
Federal Rules of Evidence 702 and 703 govern the admissibility of expert testimony. Rule 702 imposes three requirements: (1) the expert must be qualified to testify, by “knowledge, skill, experience, training, or education”; (2) the testimony must concern “scientific, technical or other specialized knowledge”; and (3)the testimony must be such as to “assist the trier of fact to understand the evidence or to determine a fact in issue.” Shay, 57 F.3d at 132; see Ware, 914 F.2d at 1002.4 Confronted with overwhelming authority to the contrary,5 as well as Agent Cooney’s extensive “firearms” expertise, appellant simply cannot prevail on a claim that the district court abused its *89discretion in ruling that the Cooney testimony met these threshold criteria.
Accordingly, the admissibility determination depended only upon Evidence Rule 703, to which we now turn:
The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence.
Fed.R.Evid. 703 (emphasis added). “The rationale for this aspect of Rule 703 is that experts in the field can be presumed to know what evidence is sufficiently trustworthy and probative to merit reliance.” 29 Charles A. Wright and Victor J. Gold, Federal Practice and Procedure § 6273, at 311 (1997). Nevertheless, Rule 703 does require that the trial judge act as an independent “gatekeeper” to ensure that there is sufficient, credible evidence that experts do rely on the specified types of sources in formulating their opinions. See Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 595-96, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993); see also Fed.R.Evid. 703 advisory committee’s note (under Rule 703, “[attention is directed to the validity of the techniques employed rather than to relatively fruitless inquiries whether hearsay is involved.”).
As noted, Corey challenges the expert testimony presented by Cooney as pure hearsay, consisting of “nothing more than [Cooney’s] recollection of what others had told him.” Specifically, Corey contends that the challenged expert' opinion — that the shotgun had been manufactured in Massachusetts, rather than Maine — was based exclusively on Cooney’s conversation with Roy Jinks, the Smith and Wesson historian at the Massachusetts plant. This claim is seriously flawed as well.
First, Corey not only glosses over the highly deferential standard of review, see Shay, 57 F.3d at 132 (clear abuse of discretion), but proffers a highly self-serving interpretation of the challenged testimony. Agent Cooney repeatedly testified that he had based the opinion that the shotgun had been manufactured in Massachusetts not only on his telephone conversation with Smith and Wesson historian Roy Jinks, but on his own customary research into technical reference manuals and materials maintained at the ATF “research libraries,” which contained information on approximately five thousand different firearms.6 Specifically, Cooney consulted the ATF “history background file” on Smith and Wesson, which contained “a notation ... about these shotguns, [and] where they’re made.” The case law clearly reflects that these are types of materials commonly consulted by firearms experts.7
*90Moreover, Agent Cooney testified that he based the opinion, at least in part, on his own knowledge and expertise as a firearms specialist, both with the ATF and in the private sector. See supra note 1. Further, Cooney confirmed that he had handled “[bjundreds of thousands of firearms,” and had “examined that type of shotgun [viz., Corey’s shotgun] before.” Thus, as the district court aptly noted, Agent Cooney himself had “acquired this information over the years.”8
Second, Agent Cooney steadfastly resisted repeated suggestions by defense counsel that he had relied exclusively on his telephone conversations with Smith and Wesson employees at the Massachusetts plant. Instead, Cooney emphasized, the telephone consultation “was ... one of my procedures in the examinations of the shotgun, what I do with every type of weapon. I check the technical files, our research library, if necessary call the factory.” (Emphasis added.) Moreover, Cooney noted explicitly that he had relied on his conversation with Jinks, “as well as the additional research.” (Emphasis added.) Finally, asked by defense counsel whether he had called the factory because his own research had proven “inconclusive,” Cooney responded: “No, sir. I always like to get two or three places to check my research.”
The dissent intimates that Cooney’s testimony was deficient because, unlike the experts in most of the cited cases, he did not rely on the markings on the firearm, such as a proof mark, a geographical notation (e.g., “Smith and Wesson, Springfield”), or a serial number.9 We respectfully disagree.
First, although firearms experts frequently rely upon weapon markings, the decisions cited in the dissent do not remotely suggest that reliance upon gun markings is required, nor that the expert opinion could not have been predicated entirely upon various other reliable eviden-tiary foundations, such as their independent research or their professional experience and expertise. Furthermore, it is clear that in certain cases an expert witness could not gain access to gun markings. See United States v. Gregg, 803 F.2d *91568, 571 (10th Cir.1986) (noting that the government is “not required to produce an actual firearm at trial, or prove the specific manufacturer or serial number of the firearm in question”). Thus, though reliance on gun markings may well enhance an expert opinion, other sound methodologies plainly are not thereby rendered unreliable per se.
Second, gun markings do not necessarily constitute conclusive evidence. See Coleman, 22 F.3d at 131 (noting that even though geographical location is stamped on weapon, the jury might fairly infer that location there reflected was the home plant of the manufacturer, not necessarily the manufacturing site); see also United States v. Horsman, 114 F.3d 822, 824-25 (8th Cir.1997) (even where gun is stamped “Made in U.S.A.” gnd “Springfield, Massachusetts,” expert was asked to state his opinion, “[b]ased on research and his expertise,” as to whether the weapon was manufactured in Springfield, Massachusetts).
The dissent further suggests that the government must establish nexus by more direct evidence, such as adducing trial testimony from the manufacturer, or introducing the manufacturer’s internal records in evidence. We have not been able to find support for this suggestion in the case law, however. More importantly, such a regimen would reinvent the “best evidence” requirement which Evidence Rule 703 was designed to relax. Cf. United States v. Simmons, 773 F.2d 1455, 1460 (4th Cir.1985) (finding that Confrontation Clause was not violated by trace forms, since “[t]he policy interest in minimizing expense and delay” caused by requiring record custodians to testify at trial “must be balanced against the [limited] utility of the Confrontation Clause to the defendant”) (emphasis added); cf. also United States v. Abbas, 74 F.3d 506, 513 (4th Cir.1996) (“Rule 703 exists so that scientific standards may be admitted as trustworthy and reliable exceptions to the hearsay rule, thereby negating the need to parade into court each and every individual either remotely or intimately involved in the creation of a particular standard.”).
Finally, appellant’s total reliance upon Davis and Trenkler is misplaced.10 In Davis, the government attempted to introduce ATF trace reports,11 and the court ruled that the trace reports came within no hearsay-rule exception. See Fed.R.Evid. 803(6) (records of regularly conducted business); 803(8) (“public records and reports”); 803(24) (residual exception). See Davis, 571 F.2d at 1356-58, 1360 n. 11. But see, e.g., Simmons, 773 F.2d at 1459 (holding that ATF trace reports meet the “residual hearsay” exception, since they possess sufficient -indicia of trustworthiness). Furthermore, Davis did not involve Rule 70S, which specifically permits expert witnesses to rely on otherwise inadmissible hearsay of a type “reasonably relied” on by experts in the field. See United States v. Harper, 802 F.2d 115, 121 (5th Cir.1986).
Similarly, Trenkler involved an ATF report admitted pursuant to Rule 803(24), rather than as foundation for expert testimony introduced under Rule 703. See Trenkler, 61 F.3d at 57-62; United States v. Maddix, 96 F.3d 311, 315 (8th Cir.1996) (ATF agent allowed to rely on trace report in reaching opinion on “interstate commerce” element, so long as agent “testified that firearms experts customarily rely upon tracing reports to determine whether firearms have been transported across state lines”) (citing Fed.R.Evid. 703). Thus, Davis and Trenkler are neither legally nor factually apposite.
*92III
CONCLUSION
As the record discloses that the district court acted well within its discretion in rejecting Corey’s narrow contention that Agent Cooney had relied on “nothing more than his recollection of what others had told him,” we need not consider whether the Cooney testimony would have been inadmissible under Rule 703 had he relied exclusively on the telephone conversation to Smith and Wesson employees. Moreover, given the categorical formulation of the argument presented by Corey on appeal, there is no need to determine whether Agent Cooney’s partial reliance on the telephone conversation with Smith and Wesson employees somehow rendered his otherwise well-supported expert opinion suspect under either the Federal Rules of Evidence or the Confrontation Clause.12 But see Gresham, 118 F.3d at 266 (noting that ATF agents may “testify on the basis of hearsay” and may “base[ ] their testimony on discussions with the manufacturers”); Ware, 914 F.2d at 1001-02 (finding no error where ATF agent also testified that he “previously contacted the manufacturer by mail and telephone”); but see also Arkwright Mut. Ins. Co. v. Gwinner Oil, Inc., 125 F.3d 1176, 1182 (8th Cir.1997) (‘Where an expert’s opinion is partly based on hearsay which does not meet the Rule 703 requirements, his opinion is nevertheless admissible if it is supported by the other independent bases upon which he relied to form that opinion.”).
Finally, as Corey challenges only the admissibility of the opinion testimony provided by Agent Cooney, there is no need to comment on the sufficiency of the government’s evidence on the nexus element. Obviously, however, the jury remained free to discredit Agent Cooney’s opinion in whole or in part.13
Accordingly, given the factual record before us, the district court acted well within its discretion in allowing the jury to consider the expert testimony provided by ATF Agent Michael Cooney relating to the “interstate nexus” element. See Shay, 57 F.3d at 132.
Affirmed.
. Cooney explained that before joining the ATF he had worked as a technical assistant and operations manager for two private com-pañíes licensed to import firearms, where he had "evaluated and classified and identified firearms."
. Cooney further testified that the weapon was operational, with a barrel-length of 30 % inches, an overall length of 50 % inches and an original magazine capacity of five rounds, but that a "plug” had been inserted which reduced the magazine capacity to two rounds.
. The dissent suggests that the standard of review should be less deferential than abuse-of-discretion, notwithstanding the fact that the entire legal argumentation in appellant’s fifteen-page brief consists of less than two pages, in which he neither cites Evidence Rule 702 or 703, nor articulates any Sixth Amendment Confrontation Clause claim. See United States v. Bongiorno, 106 F.3d 1027, 1034 (1st Cir.1997) (noting that issues raised on appeal in perfunctory manner are deemed waived); see also infra note 6. Thus, the dissent is predicated principally upon arguments not properly before us. See infra notes 10 & 12.
. Rule 702 provides:
If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.
Fed.R.Evid. 702.
. See, e.g., United States v. Dunn, 946 F.2d 615, 618 (9th Cir.1991) (holding that government may prove the interstate nexus element with expert opinion testimony); Ware, 914 F.2d at 1002-03 (noting that expert opinion will assist jury in determining "nexus,” while leaving the ultimate issue entirely to the jury); United States v. Gann, 732 F.2d 714, 724 (9th Cir.1984) (same).
The dissent contends that these cases were wrongly decided, in that for Rule 702 purposes expert testimony with respect to the place of manufacture is not "specialized knowledge,” unlike an expert opinion as to the manufacturer. None of the authorities cited by the dissent supports the novel proposition that a trial court must "deconstruct” an expert’s opinion into such discrete components. Rather, under Rule 702 the only inquiry is whether the expert opinion, taken as a whole, may assist the jury in resolving an ultimate issue of fact: in this case, whether the gun traveled in interstate commerce.
. Although Corey intimated in his voir dire and cross-examination of Agent Cooney that the ATF files themselves would be inadmissible because all the information therein was hearsay obtained and compiled by ATF agents in the field, he has not raised this claim on appeal. Accordingly, any such claim is deemed waived, and the reliance placed upon it in the dissent is unwarranted. See United States v. Owens, 167 F.3d 739, 745 n. 3 (1st Cir.1999); see also supra note 3.
Moreover, the record cannot support such a claim. Agent Cooney testified: “We have in-house technical information that’s been provided us by the factory, and other information we keep in-house that I use for reference." (Emphasis added.) Thus, the only inference the quoted testimony might support is that some of the ATF file information was factory-derived.
. See, e.g., Gresham, 118 F.3d at 266 (ATF agents "may base[] their testimony on ... corporate literature and reference materials maintained by the ATF.”); United States v. Bonavia, 927 F.2d 565, 567 n. 2 (11th Cir. 1991) ("Interstate nexus” expert may rely on examination of weapon and “consultation of reference books[.]”); Ware, 914 F.2d at 1003 (noting that, under Evidence Rule 703, firearms expert may "reasonably rely” on gun markings, “various ATF publications and lists,” and "firearms trade books, magazines, and reference materials”) (emphasis added); *90United States v. Clawson, 831 F.2d 909, 912-13 (9th Cir.1987) (holding that ATF agent's "nexus” testimony is adequately founded if predicated on "standard reference works,” such as "catalogs, firearms manuals, and reference publications”).
. See, e.g., Gresham, 118 F.3d at 266 (ATF agents "may base[] their testimony on ... their personal experience in law enforcement.”); United States v. Horsman, 114 F.3d 822, 824-25 (8th Cir.1997) (finding sufficient an expert’s testimony on cross-examination that he was not personally aware that the defendant’s gun was ever manufactured in the state where he possessed it); United States v. Wallace, 889 F.2d 580, 584 (5th Cir.1989) (finding no hearsay problem where ATF agent with 13 years of experience "testified that his conclusions were based on his ... training[ ] and experience”); United States v. Gregg, 803 F.2d 568, 571 (10th Cir.1986) (crediting weapon specialist's testimony as to the location of manufacture based entirely on witness’s personal knowledge and experience); United States v. Simmons, 773 F.2d 1455, 1460-61 (4th Cir.1985) (ATF agent with nine years’ experience, who had conducted thousands of firearms investigations, allowed to testify to location of weapon’s manufacture, based on his personal knowledge); cf. United States v. Buggs, 904 F.2d 1070, 1077 (7th Cir.1990) (permitting Indiana law-enforcement officers to testify that Smith and Wesson handguns were manufactured in Springfield, Massachusetts).
. Even if this premise were to be accepted, the record suggests that Agent Cooney did indeed rely upon the Corey shotgun "markings.” When Agent Cooney was asked to provide "a brief description of [the Corey shotgun], including the weapon type, markings, and its history,” Cooney responded that it was "a Smith and Wesson, Model 916-A, twelve-gauge, pump-action shot gun, serial number 7B1279,” "manufactured by the Smith and Wesson firearms company of Springfield, Massachusetts.” As Corey has not attempted on appeal to describe the markings on the shotgun, we can only conclude that the district court fairly inferred that the expert opinion offered by Agent Cooney was predicated, at least in part, upon an examination of the shotgun markings.
. The fifteen-page appellate brief submitted by Corey devotes but two pages to legal argumentation, and cites only Trenkler and Davis.
. These reports enable ATF agents to request the home office to trace the serial number on a firearm to the manufacturer. The ATF then requires the manufacturer to fill out a report detailing the gun’s history, and submit it to the ATF.
. The dissent mistakenly contends that the panel opinion rests on the assumption that Agent Cooney's "reliance on hearsay [viz., the phone call] is irrelevant since [he] also relied on ATF in-house files and his personal experience.” Rather, Agent Cooney's reliance on the phone call is irrelevant simply because Corey formulated his appeal so narrowly, and failed to raise the arguments the dissent regards as persuasive. See supra note 3.
Although we need not resolve the matter, we note also that the trial testimony — that Agent Cooney had followed the same procedure with "every type of weapon” — arguably might sustain the district court's discretionary ruling that the information Cooney used— including the phone confirmation — itself was "of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon a subject,” Fed.R.Evid. 703.
. The district court instructed the jury that it could "accept or reject that [expert] testimony ... [and] should consider ... [t]he witness’s education and experience and training, the soundness of the reasons given for the opinion, and all the other evidence in the case that might bear or impact on that testimony.”