Question

why where the sepoys unwilling to use the cartridges for the Enfield rifle

Answer 1

The Sepoys did not reject the Enfield rifle. They rejected the cartridges used to fire it because as a waterproofing method the British coated the paper cartridges with animal fats.

Answer 2

The sepoys were not willing to use the cartridges of the Enfield rifle.

Those cartridges were made by the fat of pig and beef.

The sepoys were from the Muslim and the Hindu communities.

Their religion opposed the use of those cartridges as cow is considered as sacred for the Hindus and pig cannot be tasted by the Muslims.