
597 S.E.2d 373 (2004)
278 Ga. 45
SILVERS
v.
The STATE.
No. S04A0800.
Supreme Court of Georgia.
June 7, 2004.
*374 Ramon J. Fajardo, Albany, for appellant.
Robert W. Lavender, Dist. Atty., Thurbert E. Baker, Atty. Gen., Raina Nadler, Asst. Atty. Gen., for appellee.
CARLEY, Justice.
Mark Wayne Silvers and three others were jointly indicted for commission of the following crimes: malice murder; three alternative counts of felony murder; four counts of armed robbery; eight counts of aggravated assault; and, burglary. Silvers was tried separately, and the jury found him guilty on *375 all counts. Determining that the verdicts on the alternative felony murder counts were vacated by operation of law and applying the principles of merger to the remaining counts, the trial court entered judgments of conviction for malice murder, three counts of armed robbery, seven counts of aggravated assault, and burglary. Silvers was sentenced to life imprisonment for murder and for one of the armed robberies, and he received sentences of 20 years' imprisonment for the remaining offenses. He filed a motion for new trial, which the trial court denied. Silvers now appeals to this Court.[1]
1. Silvers used his car to transport the other three named in the indictment to and from the scene of the crimes. He waited in the vehicle while two of them donned masks, entered the victims' trailer, fired shots and demanded money. Three of the eight occupants of the trailer were robbed of money and four were shot, one of them fatally. After his arrest, Silvers wrote a letter to the sheriff in which he claimed that he was forced to participate, and that the others had threatened him and his family. However, one of the three alleged co-conspirators was a witness for the prosecution, and he testified that Silvers was a willing participant in the events. When construed most strongly in support of the verdicts, the evidence is sufficient to authorize a rational trier of fact to find proof beyond a reasonable doubt of Silvers' guilt as a party to all the crimes with which he was charged. Jackson v. Virginia, 443 U.S. 307, 99 S.Ct. 2781, 61 L.Ed.2d 560 (1979); Simpson v. State, 265 Ga. 665, 461 S.E.2d 210 (1995).
2. Initially, Silvers was represented by appointed counsel. Subsequently, he retained an attorney to defend him. He urges that both lawyers failed to provide him with effective legal assistance. To prevail on this claim, Silvers must show that either attorney's performance was deficient and that, but for that deficient representation, there is a reasonable probability that the proceeding would have ended differently. Strickland v. Washington, 466 U.S. 668, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984). In making this showing, he must overcome the strong presumption that the lawyers' efforts on his behalf fall within the broad range of reasonable professional conduct. Jackson v. State, 277 Ga. 592, 593(2), 592 S.E.2d 834 (2004). After conducting an evidentiary hearing, the trial court found that Silvers failed to make the requisite showing. We must accept the trial court's factual findings and credibility determinations unless they are clearly erroneous, but we apply the appropriate legal principles to the facts independently. Wilson v. State, 277 Ga. 485(2), 591 S.E.2d 812 (2004).
(a) With regard to the appointed attorney, the allegations of deficient performance relate to the failure to file a demurrer challenging certain counts of the indictment. See Youngblood v. State, 253 Ga.App. 327, 328(3), 558 S.E.2d 854 (2002). According to Silvers, the armed robbery counts, which alleged that he intended to commit theft by taking the victims' money "by use of an offensive weapon, to wit: a firearm," are void because neither the specific type of gun nor the caliber of the weapon was set forth. However, such specificity in describing the weapon used to perpetrate an armed robbery is not required. That crime can be committed by the use of an offensive weapon to accomplish the theft, and the indictment sufficiently charges Silvers with commission of the offense in that manner. See Battle v. Williams, 268 Ga. 35(1), 485 S.E.2d 204 (1997). Thus, there is no merit in the assertion that counsel was deficient for failing to challenge void armed robbery counts. Compare Youngblood v. State, supra.
Silvers also contends that the aggravated assault counts are void and subject to a demurrer, because they do not allege that *376 those crimes were committed with a deadly weapon or an instrument which, when used offensively, resulted in or was likely to result in serious bodily injury. According to the indictment, the aggravated assaults were perpetrated "with a firearm, by shooting" the victims. "The term `shooting' is not susceptible of an overly broad interpretation. It clearly denotes the use of a deadly weapon. [Cits.]" Rushin v. State, 180 Ga.App. 276(1), 348 S.E.2d 910 (1986). Thus, those counts would not have been subject to a demurrer, even if the appointed attorney had filed one. Compare Smith v. Hardrick, 266 Ga. 54, 464 S.E.2d 198 (1995) (aggravated assault by use of hands, which, unlike guns, are not per se deadly weapons); Youngblood v. State, supra.
(b) The record shows that Silvers' retained lawyer consulted with him on numerous occasions, thoroughly investigated the case and was fully prepared for trial. Although he did not visit the scene of the crimes and did not hire an expert, neither action was material to an effective presentation of his client's coercion defense. The attorney is further alleged to have failed to interview and call several potential exculpatory witnesses, but Silvers did not make a proper proffer of their testimony at the evidentiary hearing. Goodwin v. Cruz-Padillo, 265 Ga. 614, 615, 458 S.E.2d 623 (1995). Moreover, such showing as he did make demonstrates that they could not give admissible testimony, in that they lacked personal knowledge of any material exculpatory fact and could only recount inadmissible hearsay.
Silvers also urges that he did not authorize trial counsel to waive his presence at the pre-trial Jackson-Denno hearing held to determine the admissibility of his custodial statement to officers. In that statement, Silvers admitted that he transported the other three alleged co-conspirators to and from the scene, but claimed that he did so only because he was coerced by threats against himself and his family. In that regard, it was completely consistent with the letter that Silvers voluntarily wrote to the sheriff and which was admitted at trial. Thus, the Jackson-Denno hearing did not result in the admission of any evidence which harmed Silvers. If anything, his oral statement to the officers corroborated and bolstered the exculpatory letter that he sent to the sheriff. Under the circumstances, Silvers has not shown that, but for the lawyer's unauthorized waiver of his presence, the outcome of the trial could have been different. See Byrd v. State, 274 Ga. 58, 60(2), 548 S.E.2d 2 (2001).
3. Douglas Roebuck, one of the three others jointly indicted for the crimes, was tried and convicted before Silvers was brought to trial. See Roebuck v. State, 276 Ga. 136, 575 S.E.2d 895 (2003). Roebuck did not testify at Silvers' trial, but he did appear at the hearing on Silvers' motion for new trial. In his testimony in that proceeding, Roebuck exonerated Silvers and corroborated the claim that he had been threatened. Silvers urges that Roebuck's testimony is newly discovered evidence requiring the grant of a new trial.
There is no newly discovered evidence. All that has changed is Roebuck's decision to testify on Silvers' behalf. "`[T]he once-unavailable defendant who now seeks to exculpate his co-defendant lacks credibility, since he has nothing to lose by testifying untruthfully regarding the alleged innocence of the defendant seeking a retrial.' [Cit.]" Hester v. State, 219 Ga.App. 256, 257(1), 465 S.E.2d 288 (1995). In addition to lacking credibility, Roebuck's testimony is cumulative of the exculpatory evidence which was presented at Silvers' trial, and is merely impeaching of the inculpatory testimony of the co-conspirator who was a witness for the prosecution. Under these circumstances, a new trial on the ground of newly discovered evidence was not authorized. Bryant v. State, 274 Ga. 798, 800(3), 560 S.E.2d 23 (2002).
4. Silvers contends that the aggravated assaults merged into the armed robberies and that, consequently, the trial court should have sentenced him only for the armed robberies. "[A]ggravated assault is not a lesser included offense of armed robbery as a matter of law, and the two offenses rarely merge as a matter of fact. [Cits.]" Lowery v. State, 209 Ga.App. 5, 8(4), 432 S.E.2d 576 (1993). The indictment alleged that the aggravated assaults were committed *377 "with a firearm, by shooting" the victims. The armed robbery counts alleged the "use of an offensive weapon, to wit: a firearm."
Thus, the aggravated assault charge[s were] based upon an actual firing of the weapon, but the armed robbery charge[s were] not. [Those] charge[s were] based only upon [the] use of the weapon to commit the robber[ies].... Under these circumstances, the subsequent firing of the weapon was a separate act of violence from the initial pointing of the weapon at the victim[s]. [Cits.] Thus, the aggravated assault[s were] not included in the armed robber[ies] as a matter of fact, and the evidence fully authorized ... separate conviction[s] and sentence[s] for the latter offense[s].
Taylor v. State, 275 Ga. 461, 462-463(1), 569 S.E.2d 520 (2002).
Judgments affirmed.
All the Justices concur.
NOTES
[1]  The crimes were committed on January 12, 2001. The grand jury indicted Silvers and the other three alleged co-conspirators on August 8, 2001. The jury returned the guilty verdicts on April 10, 2002, and the trial court entered judgments of conviction and sentenced Silvers on the following day. On April 18, 2002, Silvers filed a motion for new trial, which the trial court denied on December 2, 2003. Silvers filed a notice of appeal on December 31, 2003, and the case was docketed in this Court on January 15, 2004. The appeal was submitted for decision on March 8, 2004.
