Bullberry.com lists 45 -70 as an option for both Contender and Encore........
For the Contender they post this: ‡ The 45-70 US Government when used in the classic Contender or G2 actions should be limited in pressures by utilizing original Marlin Model 1895 loading data.
I do not see that limitation for the Encore...
Speak with Troy if you call them....