<P> There were also grievances over the issue of promotions, based on seniority . This, as well as the increasing number of European officers in the battalions, made promotion slow, and many Indian officers did not reach commissioned rank until they were too old to be effective . </P> <P> The final spark was provided by the ammunition for the new Enfield P - 53 rifle . These rifles, which fired Minié balls, had a tighter fit than the earlier muskets, and used paper cartridges that came pre-greased . To load the rifle, sepoys had to bite the cartridge open to release the powder . The grease used on these cartridges was rumoured to include tallow derived from beef, which would be offensive to Hindus, and pork, which would be offensive to Muslims . At least one Company official pointed out the difficulties this may cause: </P> <P> unless it be proven that the grease employed in these cartridges is not of a nature to offend or interfere with the prejudices of caste, it will be expedient not to issue them for test to Native corps . </P> <P> However, in August 1856, greased cartridge production was initiated at Fort William, Calcutta, following a British design . The grease used included tallow supplied by the Indian firm of Gangadarh Banerji & Co . By January, rumours were abroad that the Enfield cartridges were greased with animal fat . </P>

After the great revolt of 1857 british rule changed in that