I have extensive experience with both the .38 Special shot caps for reloading and with CCI's loaded shotshells. Most recently, and in most volume, I've used .45 ACP and .22 lr shot loads. I've killed over 15 pack rats with the .45s, and a couple more with the .22s, from a Model 63. I've also used the 63 to shoot sparrows and starlings that have gotten into my barn, without risk of damaging the sheet metal, though I did break one light bulb. Several years ago, a big, apparently rabid tomcat holed up in the corner of my barn. I didn't want him to escape, or to fight with my dog or cats. As I approached him with my Commander, loaded with the CCI .45 shotshells, he was on top of a stack of boxes about 3 feet tall, and he rose up and started snarling, hissing and spitting. When I shot him the first time, he jumped at me, and I shot him twice more in the air. He was dead when he he hit the floor, but was only about 4-5 feet from me when I fired the last shot. He'd have weighed close to 20 lbs., and I sure don't recommend using these loads on critters that big.
I used to use a lot of the reloaded .38 capsules, but had problems a couple of times with the caps not breaking up when fired. They worked well when they did break up. I like the factory loaded ones better. As to how far they are effective, it depends on what you're shooting. I've killed pack rats up to about 30 feet away with the .45s, and sparrows on the wing at up to about 25 feet, but patterns are getting pretty thin by then, and closer is better. BTW, the .45s have functioned in at least 3 of my 1911-types.