I like the same guns as I do for pheasants, prairie grouse, Huns, and the like. Those have mostly been O/U shotguns in 12, 16, and 20 ga. with 28" barrels. I used a Citori Upland Special for many years but later realized I shot longer barrels better. My most preferred are fixed choke or standard Invector/Mobil choke guns as the barrels are lighter. Whether Citori, 68x, older Miroku, Vamet, etc. I liked them.
For just bobwhites I preferred an ounce of 7.5 regardless of bore. I tried 8s but they produced more cripples than I liked as ranges opened up. It is my preference for Mearns quail too.
Gambel's and blue quail I move to heavier shot charges and often larger shot as the birds can flush at longer distances. An once and an eighth of 7.5 is a minimum and these birds are one of the places I'll think 6s have a serious place.
The little I've hunted California quail I would lean toward the loads for Gambel's and blues but bobwhite loads would probably do well too. The two years I chased them were after poor hatches so what I found were older and wiser than normal. I probably wasn't in the best habitat either which can make a difference in how well they will hold for a point.
