Probably a Snider bullet. The Snider projectile was generally 31 grams but the most likely identification is indeed Snider. The Snider rifle was developed by an American Jacob Snider, born Montgomery, Georgia about 1811 - died in England (Kilburn? London) in 1866.
His patent covered an action which could convert an 1853 Enfield muzzleloader into a breech loader. At trials against other conversions (Storms patent, Cornish Patent and so on) it won and was adopted by the British in 1866 but was superceded by the Martini Henry of Zulu War fame in 1874 though it was still used in India until nearly 1900 and still in use in the Colonies up until about then as well.
It is the original Earsplittingloudenboomer. The projectile was a great find. I used to find a lot in my grand parents front yard in the early 1980s and at the very front of the front yard about 50 yards away the shell cases.
As a kid my grandfather used to speak of them and when at High School I read this and LOVED this verse from a Rudyard Kipling Poem
'A Snider squibbed in the jungle—
Somebody laughed and fled,
And the men of the First Shikaris
Picked up their Subaltern dead,
With a big blue mark in his forehead
And the back blown out of his head.'