Lincoln's repeater is a very high-powered lever-action rifle, dealing 25 more damage than the hunting rifle. It lacks a scope, but remains accurate at long range by ignoring the bugged scope auto-aim. It also has three times the ammunition capacity of the hunting rifle and is very effective at long range in V.A.T.S.
Lincoln's repeater is located in the Museum of History. To find it, enter the Museum of History, go through the lobby and enter the room with the statue of a wooly mammoth, left of the skull hanging over the entrance to Underworld. Inside this room, next to the statue of the wooly mammoth, are some doors that lead to the Museum of History Lower Halls. Go through these doors. Next, go to the top of the stairs into a room with several broken display cases, and in the back left corner of the room will be a door that leads to the Museum of History Offices.
After entering the Museum of History Offices, go to the top of the stairs. Take a left and then a right. Go to the end of the hall, through the prison door (Very Easy lock) and into a big room with a turret. In this room you'll find a staircase. Go up these stairs. At the top of the staircase, you will see a large hole in the wall. Go through the hole, and in the back left corner of the room, you will see the body of a dead raider on the ground, a Chinese Army: Special Ops Training Manual, and a display case with Lincoln's repeater inside.
This weapon is based on the Henry Rifle. The specific example referenced in the game, with its engraved gold mounting and serial number 6, was given to President Lincoln by the New Haven Arms Company in hopes that it would influence the purchase of the rifles for use in the Civil War.