Bullet ID please ..Maynard or Burnside ?

[Randy769]

Am I even close...Cant find tape measure but looking at some google pics it looks real close to either .50 Maynard or .54 Burnside...first flat bottom bullet i have found

 

[mirage83]

Don't suppose you have a set of calipers you could borrow to get a more precise measurement of it? There's a couple of different bullet possibilities depending on exact caliber and length.