As I've mentioned in several threads, my wife and I have been exterminating ground squirrels over on our friend's ranch over the course of the last few weeks. Most of the time I've been using my Kimber bolt action .22LR, and it came with 3, 5-round magazines. I've been keeping 2 loaded magazines in my shirt pocket, and 1 in the gun, and when there's kind of a lull in the shooting, I just eject the magazine that's in the gun (regardless of whether or not there's still a round or two left in it) and shove a fresh magazine in - with the bolt closed.
Then, if another ground squirrel doesn't pop up right away, I "top-off" the ejected magazine from the pouch full of .22LR rounds in my vest or jacket pocket.
My wife does the same thing with her Ruger "American Rimfire" bolt action, only she has a 10-round and a 15-round magazine - same magazines as a 10/22.
BTW, we went ground squirrel shooting yesterday morning, and again after lunch and a nap. Ground squirrel shooting is about over for this year because the grass is getting tall, making the ground squirrels hard to spot, and they'll be going back down into their dins for their long hibernations pretty soon anyway.
We've sure killed a lot of them this spring though. I think they're like rabbits in that their populations go in cycles, and this is a big year for them. My wife, our grandson and I have probably killed somewhere around 500 ground squirrels this year. And over on our friend's ranch yesterday, it didn't seem like we've put much of a dent in the population. It seemed like every time we'd shoot one, another would pop up out of a hole not two feet away, and the ones in the tall grass behind us were "chirping" at us the whole time we were there.