Affirmed by published opinion. Judge LUTTIG announced the judgment of the court and wrote an opinion, in which Judges RUSSELL, WIDENER, WILKINSON, WILKINS, NIEMEYER, and WILLIAMS joined. Judge LUTTIG wrote a concurring opinion. Judge HAMILTON wrote an opinion concurring in the judgment. Chief Judge ERVIN wrote a dissent, in which Judges HALL, MURNAGHAN, and MICHAEL, and Senior Judges BUTZNER and PHILLIPS joined.
OPINION
LUTTIG, Circuit Judge:
We sua sponte granted rehearing en banc to consider Rodney Curtis Hamrick’s appeal from convictions resulting from his attempt to assassinate a United States Attorney with a letter bomb. A panel of our court reversed most of Hamrick’s convictions on the grounds that the bomb was neither a “dangerous weapon” under 18 U.S.C. § 111(b) nor a “destructive device” under 18 U.S.C § 924(c)(1) and 26 U.S.C. § 5861(d)-(f). For the reasons that follow, we affirm Hamrick’s convictions and his sentences.
I.
In 1987, from state prison, appellant mailed letters threatening to murder then-President Ronald Reagan. He was charged with and later pleaded guilty to threatening the life of the President of the United States in violation of 18 U.S.C. § 871(a). For this offense, he was sentenced in July 1988 to five years imprisonment by United States District Judge William M. Kidd. See United States v. Hamrick, No. 88-40 (N.D. W. Va. July 22, 1988) (unreported).
While serving this sentence at the Federal Correctional Institute at Petersburg, Virginia, Hamrick built five improvised bombs. The first was determined to have been an inoperable test bomb after it was disarmed by an Army Explosive Ordinance Detail. The next four exploded, one of them seriously injuring a fellow inmate. In connection with these latter incidents, a jury convicted Hamrick of four counts each of the unlawful manufacture of an incendiary device, 26 U.S.C. § 5861(f), possession of an unregistered firearm, id. § 5861(d), and possession of contraband in prison, 18 U.S.C. § 1791(a)(2). He was also convicted for making a bomb threat, 18 U.S.C. § 875(c), in which he threatened to blow up the United States District Courthouse in Washington, D.C., if he were not released. In November 1990, United States District Judge Robert R. Merhige, Jr., sentenced him to ten years imprisonment. See United States v. Hamrick, No. 90-12 (E.D. Va. Nov. 27, 1990) (unreported).
During the time that he was in federal prison, Hamrick also committed numerous disciplinary infractions that did not result in criminal charges.1 The most significant of these were four incidents in which he constructed improvised guns. He fired one of these guns at a fellow inmate and threatened a guard with another. He also was disciplined for making four bomb threats, threatening at various times to blow up the courthouse in Elkins, West Virginia, a United [879]*879Airlines flight, and the NAACP headquarters in Washington (twice), if he were not released from prison. Hamrick was also caught in possession of a letter containing a “smoke bomb,” which he had addressed to then-President George Bush but had not mailed.
In April 1990, while still in federal prison for threatening the life of the President, Hamrick mailed a letter to Judge Kidd on behalf of “the Nazi Socialist Republican Party” in which he threatened to kill the judge and his family. After he was interviewed about the letter by the Federal Bureau of Investigation, Hamrick sent a second letter to Judge Kidd, in which he stated his resent-, ment that the judge had reported his first letter to the FBI, and again threatened Judge Kidd’s life. On the basis of these letters, a jury found Hamrick guilty in March 1991 of threatening to assault and murder a federal judge. See 18 U.S.C.A. § 115(a)(1)(B). Hamrick was sentenced to 51 months imprisonment for this offense, and a year later, we affirmed both his conviction and sentence. United States v. Hamrick, 960 F.2d 147 (4th Cir.1992) (unpublished).
Pending prosecution on this charge, from December 18, 1990, until February 14, 1991, Hamrick was incarcerated in the Ohio County Correctional Facility in Wheeling, West Virginia. While there, Hamrick constructed an incendiary bomb from items available to him inside the jail. The bomb comprised a nine-volt battery as a power source, steel wires, three butane cigarette lighters as the explosive, and an unidentified pink substance speculated to be lip balm, which was to serve as the detonator. The plastic case of one of the lighters was filed thin; the pink substance, in which the flints from the lighters had been placed, was positioned over the thin spot; and the wires, leading to the battery and an improvised switch, were run through the pink substance. Hamrick wrapped the bomb in aluminum foil and placed it in a manila envelope between a legal pad and a piece of cardboard. The bomb was designed to detonate when the legal pad was removed from the envelope and the wires of the improvised switch touched. The resulting electrical current was supposed to heat the wire and ignite the detonator, which then would melt the plastic casings of the lighters, free the butane, and ignite it. If fully effective, the bomb could have produced a 1000-degree fireball up to three feet in diameter. This fireball would have burned the skin and eyes of anyone exposed to it. If those exposed were inhaling when the bomb detonated, the fireball could have seared their lungs, possibly resulting in death.
Hamrick addressed the envelope containing the bomb to William A. Kolibash, United States Attorney for the Northern District of West Virginia, whose office was responsible for Hamrick’s prosecution, wrote his own return address on the envelope and mailed it. On January 2, 1991, Kolibash received and opened the envelope at his office. The bomb scorched the packaging in which it had been mailed, but did not detonate.
Kolibash, realizing that the envelope contained a homemade bomb, fled his office. The United States Marshals, as well as agents from the Federal Bureau of Investigation and the Bureau of Alcohol,- Tobacco, and Firearms were called to the scene. They immediately piled sandbags around the desk and secured the office. An Army bomb disposal expert and his commanding officer were flown to Wheeling from Chambersburg, Pennsylvania. Upon arriving, the expert ordered the evacuation of the entire wing of the building in which the United States Attorney was officed. While wearing a full-body kevlar bomb suit and a kevlar helmet with an inch-thick Plexiglas shield, he X-rayed and examined the bomb. After covering it with a bomb blanket, he finally dismantled it by attaching a hook-and-line set to the bomb and, from thirty feet away and down a flight of stairs, pulling the bomb’s components apart.
Immediately after Kolibash had received the bomb, and before it had been dismantled, two FBI agents, after advising Hamrick of his Miranda rights and receiving from him a signed written waiver of those rights, interviewed Hamrick at the Ohio County Jail to determine whether the bomb would explode. Hamrick admitted to the agents that he intended the bomb to detonate within minutes of the envelope being opened. He also stat[880]*880ed that he mailed the bomb to Kolibash in retaliation for the pending prosecution. Hamrick then signed a written statement, prepared by one of the agents, in which he admitted constructing and mailing the bomb. He later sent to the United States Marshal a copy of a letter he had written to the West Virginia American Civil Liberties Union in which he again admitted involvement in sending the bomb to Kolibash.
Hamrick was charged with the unlawful making of a destructive device, 26 U.S.C. § 5861(f) (Count I); unregistered possession of a destructive device, id. § 5861(d) (Count II); unlawful transfer of a destructive device, id. § 5861(e) (Count III); mailing of a non-mailable article, 18 U.S.C. § 1716 (Count IV); attempted murder of a federal officer, id. § 1114 (Count V); use of a destructive device during and in relation to the attempted murder of a federal officer, id. § 924(c)(1) (Count VI); assault of a federal officer with a dangerous or deadly weapon, id. § 111(b) (Count VII); and use of a destructive device during and in relation to the assault of a federal officer, id. § 924(c)(1) (Count VIII).2
A jury found Hamrick guilty on all counts and the district court sentenced Hamrick to 210 months imprisonment on the convictions for attempted murder and mailing of a non-mailable article, and to concurrent 120-month sentences for assault with a deadly or dangerous weapon and for the unlawful manufacture, transfer, and possession of a destructive device. The district court also imposed the mandatory sentence of thirty years imprisonment for the section 924(c) violations, to run consecutively to Hamrick’s other sentences.
A panel of this court reversed Hamrick’s conviction on count VII on the ground that the dysfunctional bomb was not a deadly or dangerous weapon. It reversed his convictions on counts I — III, VI, and VIII on the grounds that, as constructed, the bomb was dysfunctional and therefore not a destructive device. See United States v. Hamrick, 995 F.2d 1267 (4th Cir.1993) (“Hamrick /”). The United States, at the direction of the Solicitor General, did not petition either for rehearing or for rehearing en banc of the panel’s reversal of Hamrick’s convictions and sentences on these counts.
By Order of August 20, 1993, we sua sponte granted rehearing en banc. We now affirm Hamrick’s convictions and sentences in their entirety.
II.
The panel, apparently on a finding of “plain error,” reversed Hamrick’s conviction for assault of a United States Attorney with a deadly or dangerous weapon under 18 U.S.C. § 111(b),3 reasoning that, because the bomb could not explode, it could not, as a matter of law, be a deadly or dangerous weapon. Hamrick I, 995 F.2d at 1272. We reject this reasoning and affirm en banc Hamrick’s assault conviction.
Hamrick did not advance before the panel the argument that the bomb he sent to Koli-bash was not a “dangerous” or “deadly” weapon within the meaning of section 111(b). Nor does he advance this argument before the court sitting en banc. Indeed, Hamrick’s counsel candidly conceded at argument before the full court that the bomb was a [881]*881dangerous weapon under existing Supreme Court precedent, and in particular under McLaughlin v. United States, 476 U.S. 16, 106 S.Ct. 1677, 90 L.Ed.2d 15 (1986). We believe that counsel was correct to concede this point.
In McLaughlin, a unanimous Supreme Court held, in an opinion that was barely two pages long, that an un loaded handgun used to commit an assault during a bank robbery is a “dangerous weapon” under 18 U.S.C. § 2113(d), the federal bank robbery statute.4 The Court concluded that “[t]hree reasons, each independently sufficient ” supported its conclusion:
First, a gun is an article that is typically and characteristically dangerous; the use for which it is manufactured and sold is a dangerous one, and the law may reasonably presume that such an article is always dangerous even though it may not be armed at a particular time or place. In addition, the display of a gun instills fear in the average citizen; as a consequence, it creates an immediate danger that a violent response will ensue. Finally, a gun can cause harm when used as a bludgeon.
McLaughlin, 476 U.S. at 17-18, 106 S.Ct. at 1678 (footnote omitted) (emphasis added). This reasoning applies with the same force to 18 U.S.C. § 111(b), the assault of a federal officer statute under which Hamrick was convicted. See United States v. Gometz, 879 F.2d 256, 258-59 (7th Cir.1989) (“Although the McLaughlin case interpreted 18 U.S.C. § 2113, we think that its logic applies to § 111, given that the two provisions contain identical language and are cross-referenced.”), cert. denied, 493 U.S. 1033, 110 S.Ct. 752, 107 L.Ed.2d 768 (1990). McLaughlin dictates what common sense would confirm, namely, that the bomb sent to Kolibash by Hamrick was a “dangerous weapon” within the meaning of section 111(b).5
Two of the Court’s rationales in McLaughlin — the first and the second — are specifically applicable to the case before us. As to the first of these rationales, the question obviously is not whether a dysfunctional bomb is typically and characteristically dangerous, or even whether the combination of parts constituting the bomb sent by Hamrick (assuming they exist elsewhere) is typically and characteristically dangerous, no more so than the question in McLaughlin was whether an unloaded handgun is typically dangerous. Rather, the question is whether a bomb is typically and characteristically dangerous. Of course it is, and the use for which it is produced is a dangerous one. Thus, the law may presume, as it may with respect to a handgun, that a bomb is always dangerous even though, due to the fortuity of malfunction, faulty construction, or defective design, it may in a particular ease be incapable of inflicting injury. See Gometz, 879 F.2d at 259 (zip gun was dangerous weapon, although because of design defect it could not expel metal fragments as intended).
Of course, the presumption that the bomb sent by Hamrick was dangerous was fully warranted, even though the bomb appears to have been dysfunctional. See infra at 882-883, n. 8-9 (citing cases); cf. United States v. Rushcamp, 526 F.2d 1380, 1382 (6th Cir.1975) (rocket launcher with dysfunctional firing mechanism a destructive device); United States v. Tankersley, 492 F.2d 962, 966 (7th Cir.1974) (paint-remover filled bottle with dud firecracker detonator was destructive device); United States v. Greer, 404 F.Supp. [882]*8821289, 1293 (W.D. Mich.1975) (collection of blasting materials a destructive device even though no power source), aff'd, 588 F.2d 1151 (6th Cir.1978). At trial, the government’s two experts testified that the inflammable butane contained in the lighters, if released and ignited, could have produced a large 1000-degree fireball capable of killing persons exposed to its heat. One of these experts, Warren Parker, testified that a nine-volt battery by itself could have easily generated enough heat to have melted the plastic easing of the lighters, liberating the butane within and creating an explosive cloud which could have been detonated by even the smallest spark.6 And they both testified that the substitution of other substances readily available to Hamrick inside the Ohio County Jail (such as hamburger grease or matehheads) for the pink substance actually used in the bomb or some other slight modifications in the bomb’s design (such as adding additional batteries or using thinner wire) would have rendered it fully operable.
As to the second of the McLaughlin rationales, the display of a bomb, like the display of a gun, instills fear in the average citizen, whether or not it is actually capable of inflicting injury. That this is so is amply borne out by the reaction to the bomb received by United States Attorney Kolibash. The United States Attorney fled his office in fear and summoned the United States Marshals, the FBI, and the ATF. The United States Attorney’s office was sandbagged and an Army bomb disposal expert was flown in from another state. The bomb disposal expert thought the risk of serious injury sufficiently serious to wear a bomb suit to examine the device and, even after examining it, to dismantle it by remote means.
“Congress regarded incitement of fear as sufficient to characterize an apparently dangerous article (such as a wooden gun) as ‘dangerous’ within the meaning of [§ 2113(d) ].” McLaughlin, 476 U.S. at 18 n. 3, 106 S.Ct. at 1678 n. 3 (citing 78 Cong. Rec. 8132 (1934)).7 So too for the same reason is a bomb which, unbeknownst to its recipients is inoperable, “dangerous” within the meaning of section 111(b). Every circuit court to address this or a similar issue has held accordingly. See Gometz, 879 F.2d at 259 (dysfunctional zip gun instills fear and is therefore dangerous); United States v. York, 830 F.2d 885, 891 (8th Cir.1987) (broken pellet gun a dangerous weapon under § 2113(d)), cert. denied, 484 U.S. 1074, 108 S.Ct. 1047, 98 L.Ed.2d 1010 (1988).8 Indeed, every circuit court considering even the question of whether a fake weapon that was never intended to be operable has come to the same conclusion. [883]*883See United States v. Spedalieri, 910 F.2d 707, 709 (10th Cir.1990) (“fake bomb, as a matter of law, may constitute a dangerous weapon [under section 2113(d) ], regardless of its actual capabilities, when a victim confronted with it is placed in reasonable expectation of danger”); United States v. Marx, 485 F.2d 1179, 1185 (10th Cir.1973) (fake bomb, because it placed victim in reasonable expectation of death or serious injury, was a dangerous weapon under section 2113(d)), cert. denied, 416 U.S. 986, 94 S.Ct. 2391, 40 L.Ed.2d 764 (1974); cf. United States v. Boyd, 924 F.2d 945, 947-48 (9th Cir.) (road flare, which appeared to be dynamite, a dangerous weapon under Guidelines), cert. denied, 502 U.S. 828, 112 S.Ct. 98, 116 L.Ed.2d 70 (1991).9 The same conclusion has been reached even in circumstances where there was no weapon at all — fake or otherwise— but only apparently a weapon. See United States v. Benson, 918 F.2d 1, 3 (1st Cir.1990) (feigned gun, actually a pocket knife, held in robber’s pocket, a dangerous weapon under § 2113(d)); cf. United States v. Dixon, 982 F.2d 116, 122-23 (3d Cir.1992) (hand underneath a towel, represented to be a gun, a dangerous weapon under Guidelines), cert. denied, — U.S. -, 113 S.Ct. 2371, 124 L.Ed.2d 276 (1993); United States v. Taylor, 960 F.2d 115, 116 (9th Cir.1992) (bulge in waistband, represented to be a gun, a dangerous weapon under Guidelines); but cf. United States v. Hawkins, 901 F.2d 863, 865 (10th Cir.1990) (upward departure for false claim of being armed inappropriate); United States v. Coe, 891 F.2d 405, 411 (2d Cir.1989) (same).
An assault with a dysfunctional bomb poses the same or similar dangers and gives rise to the same kind of harms as an assault with an unloaded gun. Even a dysfunctional bomb engenders in the assault victims the fear of bodily injury beyond that instilled by a simple assault, see United States v. Martinez-Jimenez, 864 F.2d 664, 666 (9th Cir.), cert. denied, 489 U.S. 1099, 109 S.Ct. 1576, 103 L.Ed.2d 942 (1989); United States v. Mahler, 891 F.2d 75, 77 (4th Cir.1989) (quoting Martinez-Jimenez and applying it to sentencing guidelines); see also United States v. Beasley, 438 F.2d 1279, 1282-83 (6th Cir.), cert. denied, 404 U.S. 866, 92 S.Ct. 124, 30 L.Ed.2d 110 (1971), fear that can, for instance, bring on heart attacks and other adverse medical consequences. See United States v. Medved, 905 F.2d 935, 940 (6th Cir.1990), cert. denied, 498 U.S. 1101, 111 S.Ct. 997, 112 L.Ed.2d 1080 (1991). Law enforcement authorities must respond to the perceived threat of explosion, driving them to more deliberate and less efficient means of responding to the assault. Martinez-Jimenez, 864 F.2d at 666. And even though it is actually incapable of inflicting the injuries it threatens, an inoperable bomb creates a danger that a violent response will ensue. See McLaughlin, 476 U.S. at 17, 106 S.Ct. at 1678. Ordinarily, this danger will arise because those threatened, their rescuers, or the police, can be expected to respond with force and possibly deadly force, and thereby endanger the safety of victims, bystanders, and even the perpetrator. See, e.g., Martinez-Jimenez, 864 F.2d at 666; Beasley, 438 F.2d at 1283. But even where, as here, the weapon has been mailed and there is little risk of retaliation against the sender which would endanger those involved, there is still an immediate danger of injury to those who flee or otherwise furiously react to the perceived threat to their lives, and to innocent bystanders. In short, the sender of an inoperable mail-bomb, although distant from his victims, sets in motion events that pose danger to human life and harm society no less so than the criminal courier who delivers the bomb to his victim by hand.
[884]*884We thus conclude as a matter of law that Hamrick’s bomb could be considered by the jury to constitute a “dangerous weapon” under 18 U.S.C. § 111(b). Accordingly, we affirm his Count VII conviction for assault of a federal officer with a dangerous or deadly weapon.
III.
The jury also convicted Hamrick for the unlawful making of a destructive device, 26 U.S.C. § 5861(f) (Count I); the unregistered possession of a destructive device, id. § 5861(d) (Count II); the unlawful transfer of a destructive device, id. § 5861(e) (Count III); the use of a destructive device during and in relation to the attempted murder of a federal officer, id. § 924(c)(1) (Count VI); and the use of a destructive device during and in relation to the assault of a federal officer, id. § 924(c)(1) (Count VIII).10 The panel reversed these five convictions, holding that the jury instructions were “plain error.” See Hamrick I, 995 F.2d at 1271-72. Relying ultimately on United States v. Malone, 546 F.2d 1182, 1184 (5th Cir.1977) (“the complete absence of explosive material would prevent the component parts ft’om being a destructive device”), the panel held that Hamrick’s bomb was not a destructive device because not all of the necessary component parts of a bomb were actually in Hamrick’s possession and working. These convictions are now affirmed by an equally divided court.
IV.
Hamrick also was convicted of sending through the mails a nonmailable article, a mechanical and chemical device which might have ignited, with the intent to injure or kill another. See 18 U.S.C. § 1716. Hamrick challenges the sufficiency of the evidence supporting this conviction, arguing that since his bomb was dysfunctional, it was not a nonmailable article.
A finding that Hamrick’s bomb was capable of operating as designed is, contrary to Hamrick’s assertions, unnecessary to support a conviction under section 1716. Nonmaila-ble matter is statutorily defined as:
explosives, inflammable materials, infernal machines, and mechanical, chemical, or other devices or compositions which may ignite or explode, ... and all other natural or artificial articles, compositions, or material which may kill or injure another, or injure the mails or other property....
Id. § 1716(a). Although Hamrick’s bomb, as constructed, may have been incapable of functioning as a bomb, it was comprised of cigarette lighters containing inflammable liquified butane. As noted, expert witnesses testified that if one of the lighters were ruptured, the butane within could easily have ignited, creating a fireball. Indeed, the plastic casing of one of the lighters had been scraped thin, further increasing the risk it might rupture and ignite during handling by the Postal Service. Cf. United States v. Merrill, 746 F.2d 458, 461 (9th Cir.1984) (.22 caliber bullets, which could have been detonated by mechanical canceling machines, were nonmailable), cert. denied, 469 U.S. 1165, 105 S.Ct. 926, 83 L.Ed.2d 938 (1985). Viewing this evidence in the light most favorable to the government, see, e.g., Jackson v. Virginia, 443 U.S. 307, 319, 99 S.Ct. 2781, 2789, 61 L.Ed.2d 560 (1979); United States v. Tresvant, 677 F.2d 1018, 1021 (4th Cir.1982), we conclude that a reasonable jury could easily have found that Hamrick mailed a device which might have ignited, and was therefore guilty of violating section 1716.
V.
Hamrick also argues that the evidence was insufficient to support a finding that he possessed the intent required for conviction either for assault, see 18 U.S.C. § 111(b), or for attempted murder, see id. § 1114, of United States Attorney Kolibash. [885]*885He argues that he had intended only to register his displeasure at being prosecuted by sending Kolibash a joke bomb, one which he never intended to detonate.
We disagree. From the evidence adduced at trial, a reasonable jury could easily have found that Hamrick mailed the bomb he had built with the intent that it would explode and kill United States Attorney Kolibash. The government’s experts testified that the bomb had been designed to explode when the envelope in which it was mailed was opened and that it was too complete to have been meant as a hoax. Moreover, in his statements to the FBI and his signed confession, Hamrick himself admitted that he had intended the bomb to explode and had mailed it to Kolibash in retaliation for being brought to Wheeling to stand trial. In his letter to the West Virginia American Civil Liberties Union, Hamrick again implicated himself in the attempted bombing. Finally, the very circumstance of Hamrick sending a bomb to the United States Attorney responsible for his prosecution supports an inference of intent. This evidence is more than sufficient to support the conclusion that Hamrick intended the bomb to explode and kill a United States Attorney. The jury did not regard the bomb as a joke (nor do we) and was not required to so consider it.
VI.
Hamrick also claims that the district court erred by refusing to instruct the jury on the theory of legal impossibility as a defense to the charge of attempted murder. The defense of legal impossibility is available where the defendant’s acts, even if fully carried out as intended, would not constitute a crime. Hamrick contends that, because his bomb was incapable of exploding, he could not have committed or attempted murder.
Had Hamrick’s acts been carried out as he intended, i.e., if the bomb had exploded when Kolibash opened the envelope, the substantive crime of attempted murder (if not murder itself) would have been committed. The defense of legal impossibility therefore was simply not available to Hamrick.
Though not denominated as such, Hamrick appears to have been actually seeking an instruction on factual impossibility. Factual impossibility exists “where the objective is proscribed by the criminal law but a ■factual circumstance unknown to the actor prevents him from bringing it about.” United States v. Conway, 507 F.2d 1047, 1050 (5th Cir.1975). However, factual impossibility is traditionally not a defense to a charge of attempt, and we now join those circuits that have expressly held that it is not a defense to an attempt crime. United States v. Medina-Garcia, 918 F.2d 4, 8 (1st Cir.1990); United States v. Contreras, 950 F.2d 232, 237 (5th Cir.1991), cert. denied, — U.S. -, 112 S.Ct. 2276, 119 L.Ed.2d 202 (1992); United States v. Peete, 919 F.2d 1168, 1175-76 (6th Cir.1990); United States v. Luttrell, 889 F.2d 806, 810 (9th Cir.1989), vacated in part on other grounds, 923 F.2d 764 (9th Cir.1991), cert. denied, — U.S. -, 112 S.Ct. 1558, 118 L.Ed.2d 207 (1992).
The district court did not err by refusing to charge the jury on either legal or factual impossibility. See United States v. Camejo, 929 F.2d 610, 614 (11th Cir.1991), cert. denied, 502 U.S. 880, 112 S.Ct. 228, 116 L.Ed.2d 185 (1991).
VIL
Hamrick also challenges three evidentiary rulings made by the district court. He contends that the court erred by allowing the government to cross-examine his expert about admitted errors in the expert’s testimony in previous cases, that his letter to the West Virginia American Civil Liberties Union — in which he admitted involvement in sending a “letter bomb” to Kolibash — was irrelevant and therefore improperly admitted, and, without explanation, that his confession was involuntary. We find these contentions to be wholly without merit. Both the allowance of cross-examination and the admission of Hamrick’s letter to the ACLU chapter were well within the sound discretion of the trial court. And there is no basis whatsoever for questioning the voluntariness of Hamrick’s confession.
[886]*886VIII.
The district court sentenced Hamrick to thirty years imprisonment for the use of a destructive device during and in relation to a crime of violence, this sentence to run consecutively to all other sentences. This sen-' tenee was imposed pursuant to 18 U.S.C.A. § 924(c)(1), which provides in pertinent part:
Whoever, during and in relation to any crime of violence ... uses or carries a firearm, shall, in addition to the punishment provided for such crime ..., be sentenced to imprisonment for five years, ... and if the firearm is ... a destructive device ... to imprisonment for thirty years.
Id. (emphasis added). Hamrick contends that the terms “firearm” and “destructive device” are interchangeable and that the district court thus should have imposed the shorter sentence prescribed for the use of a “firearm.”
While “firearm” is defined to include, inter alia, “destructive device,” see 18 U.S.C. § 921(a)(3), the terms are not strictly interchangeable; rather, a “destructive device” is a subset of “firearm,” the use of which Congress has chosen to punish more severely.11 The statute is unambiguous that the use of a destructive device during and in relation to a crime of violence shall be punished by thirty years imprisonment. The terms of imprisonment specified by section 924(c)(1), therefore, are mandatory, and the district court is without discretion to deviate from the plain command of the statute. See, e.g., United States v. Dumas, 934 F.2d 1387, 1389-90 (6th Cir.), cert. denied, 502 U.S. 1006, 112 S.Ct. 641, 116 L.Ed.2d 658 (1991); United States v. Hatch, 925 F.2d 362, 363 (10th Cir.1991); United States v. Grinnell, 915 F.2d 667, 668-69 (11th Cir.1990).
It has been suggested that a thirty year additional sentence for the use of an improvised dysfunctional incendiary bomb in the attempted assassination of a United States Attorney is too harsh. We do not share this view. However, even if we were of this view, we would have no choice but to enforce this sentence. We have no authority under the law to do otherwise.
The judgment of the district court is, in all respects, affirmed.
AFFIRMED.