I load 300 grain to 405 grain in my Henry .45-70. They are 2.500" OAL. Load recipes need to be followed, and worked up. My Lee manual has loads from 2.475 up to 2.825
2.550" is the max OAL that will function 100% in lever actions. Some have used 500 grain bullets and stretched the OAL out, but they won't feed well (if at all) through the magazine and need to be single loaded.