in the 300 dollar range it would be tough to beat a 1x4 vx2 leupold. On one power it would be fast enough for most close in work and 4x gives you enough magnification for shots out to at least 300 yards. Ive got a trigicon accupoint 1x4 on one of my ars. Its a bit more expensive then your buget but it does show me that a 1x4 will work well. Personaly if it is a self defence gun and not a long range hunting gun id have a red dot on it. the vortex strikefire is a good unit for about a 150 bucks.
