Here’s an easy task that you can perform to make your seater die fit your match bullets better. You can lap the stem of the seater so that it matches exactly the profile of the bullet. This allows the seating force to be distributed over a greater area of the jacket. This allows for a smoother, more consistent seat, without leaving dents, creases or sharp rings on your bullets. Erik Cortina, a member of Team Lapua-Brux-Borden, demonstrates this process. Erik, one of America’s top F Class shooters and skilled machinists, explains, “Here, I’m lapping the inside of my new seater stem with lapping compounds. I put a bullet into the lathe, and then lap the inside of my seating stem. I applied lapping compound to the bullet as well as the stem. You can do this with a hand-drill and bore paste. In the picture below, you can see how much contact the bullet has with the stem after it’s been lapped. This bullet is a Berger Hybrid 7mm 180-grain. ” READ Related Article about Polishing Seating Die Stems > Q1: Is Lapping Seating Stems Really Necessary? It’s helpful, but not necessary, to match your seating stem to a bullet. This is especially true if you are loading hunting or varmint ammunition. It is useful to polish the stem internally. This should remove any ring or dent that forms on the jacket of the bullet during seating. Photo credit Sierra Bullets. Sharp edges on the seating stem can cause rings to be pressed in the bullet jacket, especially when compressed loads resist downward bullet movement. Q2: Are there any downsides to this process? Not really. If you shoot a variety of bullets for a specific cartridge, you might not want to conform your stem to resemble a certain bullet type. Leave it alone. Lightly lap the stem’s inside to remove burrs and sharp edges. This will prevent the formation of a ring when seating bullets.
Photo credit Sierra Bullets
