What couldn't you kill with a rifle of any kind? Of course you can kill a hog with an 8mm.
Commonly called the 8mm Mauser, the bullet is actually 7.92mm, but that term is not in everyday use.
A 1915 Erfurt 8mm rifle is worth between $200 and $2,000 depending on its condition. The actual value varies based on individual sellers and the history of the rifle.
8mm Lebel
$450
It appears you may be asking what is the round called fired from an assault rifle. It is a round. some are 5.56mm, some are 7.62mm. some are 8mm, some are 6.2mm (New Chinese round). Most are referred to by their chamber size. Rounds are comprised to two components, the ball or bullet, and the cartridge or brass. As a whole, rounds are often referred to as cartridges as well.
It is .323" in diameter for the JS bullet and .318" for the J bullet. In other words, the bullet is a little larger than a 30-06 round.
You have a rifle which fires an 8mm cartridge, and there's a number 599 on it somewhere which may or may not be a serial number. That is all that can be derived from your question - what which 8mm cartridge it fires, not who the manufacturer is, not what model of rifle it is - the things one would need to know in order to assess the value of your rifle. So, there is no way to give an answer based on the extremely sparse information you've provided.
The 3 most common RIFLE cartridges in use in WW I were probably the 30-06 (2800 fps), the 8mm Mauser (2700 fps), and the .303 Enfield (2500 fps).
That would PROBABLY be the first rifle to use a smokeless powder cartridge- the French 8mm Lebel.
No. If you try that the gun will blow up and you might be injured. You need 8mm Mauser ammunition.
Blue Book of Gun Values