I took a penny and a 22cal bullet and compared them to your pic and it looks close but not quite a match, your round looks larger in diameter and obviously longer then a 22 long round. Can you give exact measurements of the bullet?
Your pic is close to scale when holding a penny to the computer screen so I would say its closer to a 30cal round. I compared it to a 30-30 round and it looks like a good match. Thats my guess its its an old winchester round.