The army provides a monthly downloadable excel spreadsheet giving access information and firing times for the Army Ranges, Sea Danger Area, Tynham and the Fossil Forest.  See below

or you can follow this link

https://www.gov.uk/government/publications/lulworth-firing-notice/lulworth-range-firing-times-may-2021 

Or you can call Army Range open times 01929 404714 for a recorded message