You need to save the profile that you have created for your first rifle (use the 'Save...' tabs on the main screen to do this), then change as required for the subsequent rifles and or ranges. Click the save tab again to save the new rifle setup, but make sure to give it a new name and don't overwrite your original setup.
You can create folders and organise multiple rifle / range configurations quite easily. Note that each round, rifle and range should to be saved and named separately. Then load as needed using the 'Load...' tabs.