BALDOCK, Circuit Judge.
Over the course of six days in August 2004, Defendant Samuel Rushin and an accomplice robbed six convenience stores in Wichita, Kansas, at gunpoint. In December 2005, a jury convicted Defendant on six counts of interference with commerce by robbery, in violation of 18 U.S.C. § 1951; five counts of carrying a firearm during a crime of violence, in violation of 18 U.S.C. § 924(c); one count of brandishing a firearm during a crime of violence, also in violation of § 924(c); and one count of being a felon in possession of a firearm, in violation of 18 U.S.C. § 922(g)(1). The district court sentenced Defendant to 139 years imprisonment. We affirmed his convictions on direct appeal. United States v. Rushin, 211 Fed.Appx. 705 (10th Cir.2007) (unpublished). Now before us is Defendant’s second appeal — this time from the district court’s denial of his motion, pursuant to 28 U.S.C. § 2255, to vacate or set aside his sentence. United States v. Rush-in, 2009 WL 5171781 (D.Kan.2009) (unpublished). Defendant claims entitlement to post-conviction relief because he ostensibly was denied his Sixth Amendment right to [1302]*1302counsel when his trial attorney failed to seek dismissal of the indictment based on a violation of the Speedy Trial Act (STA), 18 U.S.C. §§ 3161-3174.1 Our jurisdiction arises under 28 U.S.C. § 2255(d).
In considering the denial of a § 2255 motion for post-conviction relief, we review the district court’s findings of fact for clear error and its conclusions of law de novo. United States v. Orange, 447 F.3d 792, 796 (10th Cir.2006). This is consistent with our view that an ineffective assistance of counsel claim presents a mixed question of law and fact ultimately reviewable de novo. Id. But where, as here, the district court does not hold an evidentiary hearing, but rather denies the motion as a matter of law upon an uncontested trial record, our review is strictly de novo. See Boltz v. Mullin, 415 F.3d 1215, 1221-22 (10th Cir.2005). To succeed on an ineffective assistance of counsel claim under § 2255, a defendant has the twofold burden of establishing that (1) defense counsel’s performance was deficient, ie., counsel’s “representation fell below an objective standard of reasonableness” as measured by “prevailing professional norms,” and (2) defendant was prejudiced thereby, ie., “there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.” Strickland v. Washington, 466 U.S. 668, 688, 694, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984). Applying the applicable standards, we affirm, albeit for reasons different than those the district court tendered in denying Defendant’s motion.
I.
To secure the accused’s right to and the public’s interest in the prompt resolution of pending charges, the STA requires that a criminal trial commence “within seventy days from the filing date ... of the information or indictment, or from the date the defendant has appeared before a judicial officer of the court in which the charge is pending, whichever date last occurs.” 18 U.S.C. § 3161(c)(1). But because no two cases are alike and some, for a myriad of reasons, are slower to trial than others, included within the STA is “a long and detailed list of periods of delay that are excluded in computing the time within which trial must start.” Zedner v. United States, 547 U.S. 489, 497, 126 S.Ct. 1976, 164 L.Ed.2d 749 (2006). Experience suggests that the provision courts and counsel most often employ to toll the running of the STA’s time clock is the “ends-of-justiee” continuance provided for in § 3161(h)(7).2 Subsection (h)(7)(A) permits a district court, sua sponte or upon motion, to continue a trial setting and exclude the delay, provided the court, after considering at a minimum the factors set forth in subsections (h)(7)(B)®, (ii), and (iv), places on the record “either orally or in writing, its reasons for finding that the ends of justice served by the granting of such continuance outweigh the best interests of the public and the defendant in a speedy trial.”3 18 U.S.C. § 3161(h)(7)(A). [1303]*1303“Without on-the-record findings there can be no exclusion under § 3161(h)( [7]).” Zedner, 547 U.S. at 507, 126 S.Ct. 1976.
In United States v. Doran, 882 F.2d 1511, 1515 (10th Cir.1989), we explained that subsection (h)(7)’s “exception to the otherwise precise requirements of the [STA] was meant to be a ‘rarely used’ tool for those cases demanding more flexible treatment.” Since at least United States v. Gonzales, 137 F.3d 1431, 1434-35 (10th Cir.1998), we have insisted that where a district court grants an “ends-of-justice” continuance pursuant to § 3161(h)(7), the court articulate in some detail its reasons for doing so, lest it engender misuse of the exception. To such end, we have reasoned that “[a] record consisting of only short, conclusory statements lacking in detail is insufficient.... Simply identifying an event, and adding a conclusory statement that the event requires more time for counsel to prepare, is not enough.” United States v. Toombs, 574 F.3d 1262, 1271-72 (10th Cir.2009).
Because subsection (h)(7)(A) dictates that the district court grant an “ends-of-justice” continuance only “on the basis of its findings,” the appropriate time for the court to place its findings on the record is just prior to or contemporaneously with the grant of the continuance. 18 U.S.C. § 3161(h)(7)(A). While the decision to grant a continuance must be prospective, not retrospective, we have nonetheless acknowledged that “in some circumstances a trial court may enter its ends-of-justice balancing on the record after it grants the continuance, sometimes as late as the filing of the defendant’s motion to dismiss on [STA] grounds.” Doran, 882 F.2d at 1516. In Zedner, the Supreme Court explained:
Although the [STA] is clear that the findings must be made, if only in the judge’s mind, before granting the continuance ... the [STA] is ambiguous on precisely when those findings must be “se[t] forth, in the record of the case.” However this ambiguity is resolved, at the very least the [STA] implies that those findings must be put on the record by the time a district court rules on a defendant’s motion to dismiss under § 3162(a)(2).
Zedner, 547 U.S. at 506-07, 126 S.Ct. 1976 (quoting § 3161(h)(7)(A)).4
In the unfortunate event that seventy days, less excludable time periods, elapse without a trial, a district court has no choice but to grant a defendant’s timely-filed motion to dismiss based on a violation of the STA: “If a defendant is not brought to trial within the time limit required by section 3161(c) as extended by section 3161(h), the information or indictment shall be dismissed on motion of the defendant.” 18 U.S.C. § 3162(a)(2) (emphasis added).5 In other words, “if a [1304]*1304judge fails to make the requisite findings regarding the need for an ends-of-justice continuance, the delay resulting from the continuance must be counted, and if as a result the trial does not begin on time, the indictment or information must be dismissed.” Zedner, 547 U.S. at 508, 126 S.Ct. 1976. Because the STA is designed in part to serve the public interest, that a defendant or his counsel is responsible for all or part of the delay “does not unwind [STA] violations____ [T]he district court and government are no less responsible under the [STA] merely because it is a defendant who requests a continuance.” Toombs, 574 F.3d at 1273.
Despite the STA’s dictate, the district court may, in the sound exercise of its discretion, dismiss the charges without prejudice. In fact, “[a] violation of the [STA], by itself, is not a sufficient basis for dismissal with prejudice.” United States v. Abdush-Shakur, 465 F.3d 458, 462 (10th Cir.2006). Rather,
In determining whether to dismiss the case with or without prejudice, the court shall consider, among others, each of the following factors: [1] the seriousness of the offense; [2] the facts and circumstances of the case which led to the dismissal; and [3] the impact of a re-prosecution on the administration of [the STA] and on the administration of justice.
18 U.S.C. § 3162(a)(2). Absent a showing of appreciable prejudice to the defendant, a district court generally should dismiss serious charges without prejudice under § 3162(a)(2) unless the delay is extended and attributable to “intentional dilatory conduct, or a pattern of neglect on the part of the Government.” United States v. Saltzman, 984 F.2d 1087, 1093 (10th Cir. 1993); see United States v. Artez, 290 Fed. Appx. 203, 207 (10th Cir.2008) (unpublished) (opining that defendant’s showing of “some prejudice from the delay ... was not sufficient to compel dismissal with prejudice”). A dismissal without prejudice, in turn, permits the Government to return “a new indictment ... within six calendar months of the date of the dismissal” in the event the statute of limitations has run. 18 U.S.C. § 3288.
II.
On August 27, 2004, Defendant made his initial appearance on a two-count indictment relating to one of the six robberies with which he and his cohort were ultimately charged. Absent excludable delays, the STA required that Defendant’s trial begin seventy days post, or originally no later than November 5, 2004. The district court scheduled trial for October 19, 2004. From that point forward, things went awry. At an October 4 status conference, Defendant made an oral motion for a continuance of the October 19 trial date. On October 7, the district court granted Defendant’s first motion for a continuance absent any apparent objection by the Government, and continued the trial until November 30, 2004. The court’s sole finding was that the period of delay “was excludable time as provided for in 18 U.S.C. § 3161(h)( [7]) in that the ends of justice served by granting the continuance outweigh the best interest of the public and the defendant! ] in a speedy trial.” Defendant next filed a written motion to continue on November 16. On November 29, the district court granted Defendant’s second motion for a continuance without objection, and again purportedly continued the trial pursuant to subsection (h)(7). In addition to an “ends-of-justice” finding, the court added a second finding to its second order of continuance, namely, “that counsel for [1305]*1305[Defendant] states that additional time is needed to confer with [Defendant] and conduct investigation in the case to prepare for trial or other disposition of this matter.” The court rescheduled trial for January 11, 2005. Then, on January 6, the court, sua sponte and without prior notice or hearing, ordered the trial continued a third time, until February 23, 2005. The court provided no record explanation for its action.
Meanwhile, Defendant, on February 11, 2005, made his initial appearance on a superceding indictment charging him in thirteen counts with criminal misconduct related to all six robberies. Assuming the superceding indictment reset the STA’s time clock at least as to the charges arising out of the five robberies uncharged in the original indictment, the new clock originally was set to expire on April 22, 2005.6 On the same day, February 11, Defendant moved a third time to continue the trial still set at this point for February 23. On February 21, the district court granted the motion once again absent objection, and rescheduled the trial, this time for April 5, 2005. The court’s findings contained in its fourth order of continuance were identical to the findings contained in its second order. The saga continued (no pun intended) when on the day set for trial, April 5, Defendant’s counsel filed a motion for a competency evaluation of his client. The court granted the motion the same day and vacated the trial setting indefinitely.7 Following receipt of Defendant’s psychiatric evaluation report, the court held a competency hearing on October 11, 2005 and found Defendant competent to stand trial. On October 18, the Government filed a motion, to which Defendant did not object, to reschedule the trial for November 29, 2005. On October 19, the court, “being satisfied that good cause exists” continued Defendant’s trial to November 29. Again, the court simply found “that the ends of justice served by taking such action outweigh the best interest of the public and the defendant ] in a speedy trial.” Defendant’s jury trial commenced on November 29 and concluded on December 7, 2005.
III.
In his § 2255 motion for post-conviction relief based on ineffective assistance of counsel, Defendant relied on the Supreme Court’s decision in Zedner to assert that his right to a speedy trial as defined in the STA was violated because the district court failed to make adequate on-the-record findings to support its numerous “ends-of-justice” continuances pursuant to § 3161(h)(7). The Government did not disagree with Defendant’s contention that under Zedner1 s rationale the district court’s findings related to its various “ends-of-justice” continuances were insufficient. Nor did the Government dispute Defendant’s claim that his trial commenced outside the STA’s time limits even excluding the period during which Defendant’s competency was at issue.8 Instead, [1306]*1306the Government pointed out that the Supreme Court decided Zedner six months after Defendant’s conviction, and that pri- or thereto, both counsel and the court were following “the legal and customary practice regarding the different continuances.” Rushin, 2009 WL 5171781, at *3. The district court agreed with the Government and denied Defendant’s motion:
Rushin was convicted on December 7, 2005 ..., but Zedner was not decided until June 5, 2006. Rushin’s counsel was not ineffective for failing to anticipate a future development in the law. See United States v. Harms, 371 F.3d 1208, 1212 (10th Cir.2004). Rushin has not demonstrated that his attorney’s performance fell below an objective standard of reasonableness. Strickland analysis utilizes a two prong test, and since Rushin did not meet the first prong, the court finds it unnecessary to address the second prong.
Id.
For reasons painfully apparent from our discussion of the controlling case law construing the STA, the Government on appeal abandons any claim that Zedner was a “future development in the law.” Since at least our 1998 decision in Gonzales and arguably as early as our 1989 decision in Doran, we have insisted that a district court granting an “ends-of-justice” continuance under the STA articulate in more than a cursory fashion its reasons for doing so. Thus, the question on appeal is not whether the STA was violated in this case, for no one disputes that it was.9 Rather the question is whether the performance of defense counsel was constitutionally ineffective when, notwithstanding the STA violation, he failed to move to dismiss the superceding indictment prior to trial.
A.
Consistent with the Strickland standard, we first address the performance of Defendant’s trial counsel under an objective standard of reasonableness. Just this term, the Supreme Court reiterated that “[a] court considering a claim of ineffective assistance must apply a ‘strong presumption’ that counsel’s representation was within a ‘wide range’ of reasonable professional assistance.” Harrington v. Richter, — U.S. -, 131 S.Ct. 770, 787, 178 L.Ed.2d 624 (2011) (emphasis added) (quoting Strickland, 466 U.S. at 689, 104 S.Ct. 2052).
[1307]*1307Recognizing the “temptation for a defendant to second-guess counsel’s assistance after conviction or adverse sentence,” ... counsel should be “strongly-presumed to have rendered adequate assistance and made all significant decisions in the exercise of reasonable professional judgment.” To overcome that presumption, a defendant must show that counsel failed to act “reasonably considering all the circumstances.”
Cullen v. Pinholster, — U.S. -, 131 S.Ct. 1388, 1403, 179 L.Ed.2d 557 (2011) (quoting Strickland, 466 U.S. at 688, 690, 104 S.Ct. 2052). In other words, “[t]he challenger’s burden is to show ‘that counsel made errors so serious that counsel was not functioning as the “counsel” guaranteed the defendant by the Sixth Amendment.’ ” Harrington, 131 S.Ct. at 787 (emphasis added) (quoting Strickland, 466 U.S. at 687, 104 S.Ct. 2052).
In support of his claim that his trial counsel’s performance was deficient, Defendant posits “there was no downside to moving to dismiss the indictment.” Defendant states that in the worst case scenario the district court would have dismissed the charges without prejudice, in effect requiring the Government to seek a new indictment.10 Defendant elaborates as follows: If his defense counsel had moved to dismiss the indictment, the district court “may or may not” have dismissed the indictment without prejudice. If the district court had dismissed the indictment without prejudice, the grand jury “may or may not” have reindicted him on the same charges. If the grand jury had reindicted him on the same charges, he “may or may not” have gone to trial on those charges.
We categorically reject any suggestion that because Defendant now appears to have had “nothing to lose,” his trial attorney necessarily acted unreasonably within the meaning of the Sixth Amendment by failing to file a motion to dismiss. Rarely in hindsight would a defendant — especially one who stands convicted of serious offenses and sits imprisoned for a substantial number of years— appear to have had something to lose by filing such a motion. Yet not every decision on the part of defense counsel to forego filing a motion to dismiss upon an apparent violation of the STA is suspect under Strickland’s first prong. Unlike a panel of federal appellate judges, defense counsel “observe[s] the relevant proceedings, kn[ows] of materials outside the record, and interaet[s] with the client, with opposing counsel, and with the [trial] judge. It is ‘all too tempting’ to ‘second-guess counsel’s assistance after conviction or adverse sentence.’ ” Harrington, 131 S.Ct. at 788 (quoting Strickland, 466 U.S. at 689, 104 S.Ct. 2052). Defendant “may or may not” have had something to lose by filing a motion to dismiss. Defendant “may or may not” have lost the progress that his counsel had made in plea negotiations with the Government to that point. Defendant “may or may not” have lost the favor of a district court that had granted him multiple continuances to date. Because possibilities without proof are endless, they are no measure of counsel’s performance. Defendant does not carry his burden to show his defense counsel’s performance was constitutionally deficient simply by telling us that “there was no downside to moving to dismiss.”
[1308]*1308In formulating a defense strategy, counsel is entitled to “balance limited resources in accord with effective trial tactics and strategies,” or, in other words, to critically undertake a cost/benefit analysis of any proposed course of action. Id. at 789 (emphasis added). Rarely, if ever, can we acquire from an appellate record a complete understanding of all the intangible factors that influenced a defense counsel’s decision not to undertake a particular course of action. What we can say based on the record circumstances of this particular case, however, is that a reasonable attorney in the sound exercise of his or her professional judgment arguably might have decided to forgo the filing of a motion to dismiss the indictment as largely ineffective, an imprudent use of limited resources, or even unwarranted gamesmanship. See Zedner, 547 U.S. at 502, 126 S.Ct. 1976 (recognizing a defendant might “forgo moving to dismiss”). Let us explain why.
A district court does not have unfettered discretion to dismiss an indictment with prejudice for a violation of the STA. See Abdush-Shakur, 465 F.3d at 462. Whether a district court has abused its discretion “depends, of course, on the bounds of that discretion and the principles that guide its exercise.” United States v. Taylor, 487 U.S. 326, 336, 108 S.Ct. 2413, 101 L.Ed.2d 297 (1988). Here, the three nonexclusive factors set forth in § 3162(a)(2) bound the district court’s discretion in such a manner that we may say, with a degree of confidence, that the district court would have abused its discretion in dismissing the indictment other than without prejudice. The charges against Defendant were quite serious — six robberies with a firearm over the course of six days resulting in thirteen counts of criminal misconduct. By our calculation, Defendant’s mandatory minimum sentence was 132 years imprisonment. See Rushin, 2009 WL 5171781, at *1. Furthermore, the only significant period of nonexcludable delay in which Defendant was not complied was the 31 days, more or less, resulting from the district court’s sua sponte continuance on January 6, 2005. See Saltzman, 984 F.2d at 1092-95 (holding a seven-month delay insufficient, in itself, to warrant a dismissal with prejudice). Defendant meanwhile moved for three continuances, resulting in 127 days, more or less, of nonexcludable delay, and agreed to another continuance, resulting in 41 additional days, more or less, of nonexcludable delay. See Artez, 290 Fed.Appx. at 207 (reasoning the Government should not be penalized for “delays in which the defendant was complicit.”). As to the impact of counsel’s performance on the administration of justice, Defendant asserts that if his trial attorney had filed a motion to dismiss on the basis of a STA violation, the necessary grant of the motion likely would have improved the strained relationship between counsel and his client, and may have resulted in a plea deal and substantially reduced sentence for the latter. But absent some testimony or offer of proof to that effect, such abstract claims do not persuade us.
To be sure, we do not discount the possibility that some criminal defense attorneys may have moved to dismiss the indictment in this case. The question under Strickland ’s performance prong, however, is not whether counsel’s representation “deviated from best practices or most common custom.” Harrington, 131 S.Ct. at 788. Instead, the question is whether defense counsel’s failure to file a motion to dismiss, if error at all, was an error “ ‘so serious that counsel was not functioning as the “counsel” guaranteed the defendant by the Sixth Amendment.’ ” Id. (quoting Strickland, 466 U.S. at 687, 104 S.Ct. 2052). Surely something was to be gained, howev[1309]*1309er slight, by filing such motion because the Supreme Court has said so: “Dismissal without prejudice is not a toothless sanction: it forces the Government to obtain a new indictment if it decides to reprosecute.” Taylor, 487 U.S. at 342, 108 S.Ct. 2413. This possibility alone encourages Government compliance with the STA, thus promoting the STA’s sound administration and furthering the public interest. See Zedner, 547 U.S. at 499, 126 S.Ct. 1976. A defendant too “may derive some benefit” from a dismissal without prejudice: “For example, the time and energy that the prosecution must expend in connection with obtaining a new indictment may be time and energy that the prosecution cannot devote to the preparation of its case.” Id. at 503 n. 5, 126 S.Ct. 1976 (emphasis added). But given the dearth of evidence Defendant presents to support his claim of deficient performance, we are loathe to conclude that the Sixth Amendment required his defense counsel to avail him of the indeterminate benefit of a motion to dismiss and place on the Government the corresponding burden to reindict.
When counsel focuses on some issues to the exclusion of others, there is a strong presumption that he did so for tactical reasons rather than through sheer neglect. ... That presumption has particular force where [as here] a petitioner bases his ineffective-assistance claim solely on the trial record, creating a situation in which a court may have no way of knowing whether a seemingly unusual or misguided action by counsel had a sound strategic motive.
Yarborough v. Gentry, 540 U.S. 1, 8, 124 S.Ct. 1, 157 L.Ed.2d 1 (2003) (per curiam) (internal quotations omitted). Defendant simply has not overcome the “strong presumption” that his defense counsel performed adequately under Strickland’s first prong because Defendant has not shown his defense counsel’s performance, under the circumstances presented, “fell below an objective standard of reasonableness” as measured by “prevailing professional norms.” Strickland, 466 U.S. at 688, 104 S.Ct. 2052.
B.
Because Defendant has not proven his trial counsel’s performance was constitutionally deficient as required by Strickland’s first component, we need not address Strickland’s second component which requires us to ask whether counsel’s performance prejudiced Defendant. See id. at 697, 104 S.Ct. 2052. We do dispel any notion, however, that Defendant was somehow prejudiced because he was tried and convicted on an indictment that should have been dismissed without prejudice. Defendant argues that if the pending indictment against him had been dismissed, the result of the proceeding against him necessarily would have been different, notwithstanding any subsequent course of events. Defendant grounds his argument in the Court’s oft-repeated words from Strickland that to establish prejudice, “a challenger must demonstrate ‘a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.’ ” Harrington, 131 S.Ct. at 787 (quoting Strickland, 466 U.S. at 694, 104 S.Ct. 2052).
Unlike Defendant, we do not confine our reading of the term “proceeding” in the foregoing excerpt to those court processes related to a particular indictment. Prejudice is the touchstone of Strickland’s second component. The standard measure of prejudice in the context of an ineffective assistance of counsel claim is the effect an attorney’s deficient performance had on the result or outcome. In no meaningful sense has Defendant established a reasonable probability that the result or outcome of the “proceeding” to which he was sub[1310]*1310jected would have differed if the indictment on which he stands convicted had been dismissed without prejudice. Rather, in all likelihood the Government would have reindicted Defendant, placing him in the same posture as before the dismissal. See Zedner, 547 U.S. at 499, 126 S.Ct. 1976 (recognizing that where charges are dismissed for a violation of the STA without prejudice “the prosecutor may of course seek — -and in the great majority of cases will be able to obtain — a new indictment”).
“A reasonable probability is a probability sufficient to undermine confidence in the outcome.” 11 Strickland, 466 U.S. at 694, 104 S.Ct. 2052. The reasonable probability standard “asks whether it is ‘reasonably likely’ the result would have been different.” Harrington, 131 S.Ct. at 792 (quoting Strickland, 466 U.S. at 696, 104 S.Ct. 2052). Only where “[t]he likelihood of a different result [is] substantial, not just conceivable,” can we say confidence in the outcome is undermined. Id. One surely can conceive of a different outcome here if Defendant’s trial counsel had moved to dismiss the indictment based on a violation of the STA. The end result “may or may not” have been different. But Defendant in no sense has proven the substantial likelihood of a result different from that he now faces.12
AFFIRMED.