I can do midrange with a pistol.You cant?Oh well,have fun being lunch.At any rate small calibure or not a bullets a bullet and a head is still a head.And anyways military bases would be locked up.Even if you got the keys to get in youd have top get past people who died in the base and even then they dont just leave guns lying around.They do have an armery were the guns are stored and im pretty shure thats under lock and key....
I see your point, and I guess it comes down to preference and personal experience. Tearing target dummies in half from a 300m distance with 90% accuracy felt better for me than shooting a glock 17, so I guess my opinion may be severely biased.
Under zombie attack conditions, I'd rather have to aim for center body mass (much larger target) than aiming for the head.
Additionally, where I come from guns are a rarity among civilians. Your best bet to get one would be either a hunter's rifle, or something from a police or military base. Granted, they'd be under lock and key, but that would be only an inconvenience in most situations. Most reinforced doors and locked gun cabinets open easily if you can tow them to a car or jeep.
And about people who died in the base... Statistically, an army base should be a lot safer than any other infected place, given the fact that since the beginning of the infestation 100% of the survivors were probably trained for combat and had immediate access to firearms and equipment. Which means, even in the case there are no survivors by the time you reach it, the zombie ranks will be considerably thinned.