It very definitely looks like a dropped muzzle loader ball, possibly rifle or pistol. The exact measurement of the ball in 1/1000's of an inch gives the caliber. Bullets are weighed in grains, so a lead ball 9.65 grams = 148.9 grains, which in turn works out to be .46 caliber. Muzzle loading rifles use a ball smaller than bore size, and the difference is made up with greased patch material. In my .50 caliber rifle I used a .490 ball with .017 patch. Cap and ball revolvers use an over size ball and actually cut a ring of lead off the ball when it is loaded, so it's possible that your ball is for a .44 caliber revolver like the 1861 colt which looks like this.
<img src="http://www.treasurenet.com/forums/attachment.php?attachmentid=1035419"/>
The revolver is loaded by placing powder in the cylinder first.
<img src="http://www.treasurenet.com/forums/attachment.php?attachmentid=1035420"/>
Then the ball is placed on top, and is rammed down on the powder using the lever under the guns barrel, and this cuts a small ring of lead off the ball.
<img src="http://www.treasurenet.com/forums/attachment.php?attachmentid=1035422"/>
