The specific facts -- found by the trial Judge on conflicting testimony at a voir dire -- articulating with specificity (see Commonwealth v. Silva, 366 Mass. 402, 406 ) the defendant's actions, which Officer McKenzie saw as the police arrived in response to a "trouble call," reasonably justified the officer in reaching for the front of the defendant's waist, where he found a gun. See Commonwealth v. Dottin, 353 Mass. 439, 442 (1968); Commonwealth v. Hawkes, 362 Mass. 786, 789 (1973); Commonwealth v. Almeida, 373 Mass. 266, 271-272 (1977); cf. Commonwealth v. McGrath, 365 Mass. 631 (1974); Commonwealth v. Silva, supra at 407. See generally Terry v. Ohio, 392 U.S. 1 (1968). There is no indication of "calculated harassment" (Commonwealth v. Hawkes, supra at 789) or that the action of the police officer was a pretext to look for other things such as narcotics rather than the result of a genuine apprehension that the defendant had a gun. See Commonwealth v. Anderson, 366 Mass. 394, 400-401 (1974); cf. Commonwealth v. McGrath, supra at 632; Sibron v. New York, 392 U.S. 40, 64-65 (1968). This case is distinguishable from People v. LaPene, 40 N.Y.2d 210, 221-226 (1976), relied on by the defendant, in which the police, who entered a barroom on the basis of a radio call that a person described in the call was in the barroom and armed, saw someone who answered that person's description but, unlike our case, saw nothing to corroborate the information that he had a gun. Cf. Commonwealth v. Anderson, supra at 399-401; United States v. Hernandez, 486 F. 2d 614 (7th Cir. 1973), cert. denied, 415 U.S. 959 (1974).