How to Determine Proper Bullet Seating Depth for YOUR Gun

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Tools:

 
  1. A cartridge case that has been fired in your gun, and not resized.
  2. A bullet of the type to be used, with a full, undamaged nose.
  3. Calipers.
  4. A dark felt-tipped marker.
 

 

Process:

 

Step 1

Insert the bullet into the neck of the fired case. It should fall freely into the case, with no resistance.

Step 2

Remove the bullet from the fired case and press the case neck lightly on a flat surface to create a small indentation or flat surface in the case neck so that it will grip the bullet.

Step 3

Insert the bullet, base first, into the case so that the case just grips the bullet by itself.  Just get the bullet started into the case—don’t seat it too deeply.

Step 4

Completely color the bullet with the marker.

Step 5

Gently insert the case and bullet into the chamber of the firearm, and close the action. Do not pull the trigger.

Step 6

Carefully open the action and gently remove the case.

Step 7

Retrieve the bullet. It will either be stuck up in the lands of the barrel or still in the case. If the bullet is stuck in the lands, it can be removed by tapping the butt of the gun on the ground. Or, it can be dislodged by gently pushing it out with a cleaning rod. If the bullet is still in the case, then gently remove it with your fingers, taking care not to mar the ink, and proceed to step 8.

Step 8

During Step 5, the lands will have contacted the bullet and pushed it back into the case, causing the case neck to scrape the ink off of the bearing surface of the bullet. Simply push the bullet into the case until the edge of the case neck is just to where the ink has been scraped off.

Step 9

Carefully measure the overall length of the dummy cartridge. This overall length is called your “rifle seating” depth. It is where the bullet contacts the lands of the barrel. This length is different for every different type of bullet, as it depends upon the shape of the ogive (the taper) and the meplat (the tip of the nose) of the bullet. This process should be repeated three or four times to obtain a consistent average.

Step 10

A. Set your seating die to seat at a depth between .015 and .03 inches less than your rifle seating depth.

B. Lightweight bullets may need to be seated further from the rifling. A depth of one bullet diameter inside the case neck gives good alignment and neck tension for ignition.

C. The overall length must be short enough to function through the magazine.