Hello, Jason F. That 2.125" brass is the length of the original brass. Winchester, for some reason decided to shorten their .30-30 & .38-55 brass many years ago. This can have a bad effect on the use of cast bullets..especially if black powder is used..as the bullet tends to swell into the excess space between case mouth and chamber end..and then is squeezed down again going into the throat..not a good thing for accuracy!
I have found by actual measurement, that most chambers are much longer..some as much as .050" than factory brass..much longer than the recommended trim length indicate..most of us are probably trimming our already too short brass even shorter! Best of luck!