Gas turbine combustor

A fuel/air mixing apparatus, such as a main swirler assembly (400) comprising a sleeve (410), provides for additional air entry around the perimeter of a bore (440) through which passes a fuel/air mixture. The additional air reduces or eliminates flashback during operation of a gas turbine comprising the assembly (400). In some embodiments, a plurality of gaps (464) exists between spaced apart tabs (462) along a downstream end (460) of the sleeve (410). During gas turbine operation, air flows through both a flashback annulus (411) and the gaps (464). In other embodiments, a plurality of holes are placed upstream and in line with the tabs (1004) to supplement the air flow through gaps (1006). In yet other embodiments, rows (1102) of holes (1104) are provided to supplement the airflow. Downstream ends (460, 1218) may interface with a downstream-oriented lip (460) or with an upstream-oriented lip (1224). The interfacing may comprise a fit effective to damp vibration and to increase the natural frequency.