When Burke and Tilson enter the private office Burke is on Tilson's left. He is not shown to move at any time, yet when the bodyguard approaches the police officers Burke is now on Tilson's right. There was no sign or reason for the switch in places.
The shooter in the gunfight emptied the magazine of the M1/M2 Carbine he was using, but Captain Burke fired nine shots from his six shot .38 caliber police revolver without reloading.
The rifle used in the killing at the beginning was a folding stock paratrooper version of the U.S. Army's WW2/Korean war M1 or M2 Carbine. Is it fitted with a blank firing attachment which would NOT have been used with live ammunition. In addition the sound of the shot is not the sound of an M1/M2 Carbine firing but a more powerful full power cartridge.
The .357 Magnum is a handgun round. It is a lengthened slightly more powerful version of the .38 Special. It is not used in high powered rifles. A hunter would know this.
The murder victim was killed with a .30 M1 Carbine or 7.62 x 33 mm bullet. The police would have found the round. None of the rifles confiscated for testing would be capable of loading and firing this intermediate round.