Mark Medearis pleaded guilty to possession of a firearm by an unlawful user of a controlled substance, see 18 U.S.C. § 922(g)(3), possession of an unregistered short-barreled shotgun, see 26 U.S.C. §§ 5841, 5845(a), 5861(d), and possession of a stolen firearm, see 18 U.S.C. § 922(j). The district court sentenced Mr. Medearis to five years of probation. The United States appeals, contending that the sentence is unreasonable. We remand for re-sentencing.
Pursuant to a valid warrant, local and federal officials searched Mr. Medearis’s premises for stolen property. There they found, among other items, a short-barreled shotgun that was not registered to Mr. Medearis in the National Firearms Registration and Transfer Record as required by § 5841 and § 5845(a)(1), a Savage 30-06 caliber bolt-action rifle that had been reported stolen, and some marijuana and methamphetamine. Mr. Medearis admitted to law-enforcement officials that he used both drugs. After being indicted, he pleaded guilty to all counts.
The probation office prepared a pre-sentence report that calculated Mr. Me-dearis’s sentencing range as forty-six to fifty-seven months’ imprisonment. The district court at sentencing first noted the applicable range, but then mentioned that many of Mr. Medearis’s friends and family members had written the court, contending that Mr. Medearis had turned his life around and asking for some form of community alternative to incarceration. The court stated that it believed these letters and was convinced that Mr. Medearis had *920indeed reformed; it acknowledged the seriousness of Mr. Medearis’s offenses, but concluded that incarceration was not necessary to keep Mr. Medearis from re-offending. The court therefore sentenced Mr. Medearis to five years of probation for each count, to be served concurrently.
The government argues on appeal that the district court abused its discretion in sentencing Mr. Medearis to probation. When the district court has correctly calculated the guidelines sentencing range, as it did here, the only remaining issue is whether the ultimate sentence is reasonable. United States v. Booker, 543 U.S. 220, 261-62, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). Our review for reasonableness is akin to what we do under an abuse-of-discretion standard. United States v. Goody, 442 F.3d 1132, 1134 (8th Cir.2006). Thus a sentencing court may act unreasonably if it fails to consider a matter of relative importance, gives significant weight to an improper or irrelevant matter, or arrives at a sentence outside of the range justified by the facts of the case. See United States v. Haack, 403 F.3d 997, 1004 (8th Cir.2005), cert. denied, — U.S. -, 126 S.Ct. 276, 163 L.Ed.2d 246 (2005).
A sentence within the applicable guideline range is presumptively reasonable. United States v. Lincoln, 413 F.3d 716, 717-18 (8th Cir.2005), cert. denied, — U.S. -, 126 S.Ct. 840, 163 L.Ed.2d 715 (2005). When a district court wishes to impose a sentence outside that range, it must justify the variance on the basis of the matters listed in 18 U.S.C. § 3553(a). As the size of the variance grows, so too must the reasons that warrant it. United States v. Larrabee, 436 F.3d 890, 892 (8th Cir.2006). And if a court imposes a sentence dramatically lower or higher than what the guidelines recommend, it must show exceptional facts that make the proposed sentence a reasonable one. See id.
Mr. Medearis contends that the government’s position is that any sentence that varies from the sentencing guidelines is unreasonable. We do not construe the government’s argument to be so broad as that. Instead, the government merely argues that the district court should give the sentencing guidelines considerable weight when deciding the ultimate sentence that should be imposed. Indeed, this argument seems entirely correct, since § 3553(a)(4) requires courts to consider the guidelines range when sentencing a defendant. But to consider the guidelines is not to be ruled by them. As we indicated in Lincoln, 413 F.3d at 718, a defendant may rebut the presumption that a guideline sentence is reasonable. In fact, district courts must vary from the guidelines range in those “highly unusual circumstances” where other § 3553(a) matters would render a sentence within them unreasonable. United States v. Lazenby, 439 F.3d 928, 933 (8th Cir.2006).
After reviewing the facts of this case, we conclude that the district court abused its discretion by sentencing Mr. Medearis to only five years of probation. At the sentencing hearing, the district court considered some § 3553(a) matters, such as the need to keep Mr. Medearis from committing further crimes. But the court paid little notice to other relevant matters, such as the requirement in § 3553(a)(2)(B) that a sentence should deter others from committing similar crimes. Indeed, the district court explicitly noted that a sentence of probation “would do little to deter others,” but thought probation would be sufficient to keep Mr. Medearis from re-offending. General deterrence, however, is one of the key purposes of sentencing, and the district court *921abused its discretion when it failed to give that matter its proper weight.
In addition, we believe that the district court abused its discretion in not giving proper weight to the seriousness of Mr. Medearis’s offenses. Law-enforcement officers found stolen property throughout Mr. Medearis’s residence, including a high-powered rifle; and federal law strictly regulates the possession of short-barreled shotguns because such weapons are easily concealed and extraordinarily lethal. The risk that the rifle and the shotgun posed, moreover, was considerably increased by Mr. Medearis’s use of illegal drugs such as methamphetamine. In all, the offenses to which Mr. Medearis pleaded guilty were of a very serious nature. The district court stated that had this been the only matter, it would have sentenced Mr. Medearis to the guidelines range. But to impose a sentence of only probation indicates that the district court paid too little attention to the seriousness of Mr. Medearis’s crimes and what a just punishment for those offenses should be.
Finally, the district court’s sentence of probation fails to meet the requirement that sentences are to be crafted so as to “avoid unwarranted sentence disparities among defendants with similar records who have been found guilty of similar conduct.” 18 U.S.C. § 3553(a)(6). Other defendants who plead guilty to the conduct that Mr. Medearis admitted will almost certainly receive sentences that include some term of incarceration.
While Mr. Medearis’s rehabilitation may well be entitled to some weight, it cannot be allowed to trump all the other considerations listed in § 3553(a). We therefore conclude that the district court imposed an unreasonable sentence in this case, and we vacate the judgment of the district court and remand for re-sentencing consistent with this opinion.