How do you determine the proper seating depth for bullets (9mm 125 fmj) of unknown manufacture? Thanks for your help.

Rule #1

Make sure it is shorter than magazine length.

Rule #2:

Make sure at least half a caliber of the bullet shank is in the case.

#1 - I don`t personally load the 9MM!

#2 - From everything I`ve read the 9MM is known to alter pressures with little changes in seating depth.

I`d load a few rounds at the starting load listed for that wgt/type of bullet at the max SAAMI lenght or lenght listed for another brand bullet in your manual that`s close in shape and of the same wgt and see if they fit my magazine. If so try them in the pistol and see if feed and ejection is fully RELIABLE. If not try seating deeper in small increments ~0.005" / .010" useing the same starting load until they run through the pistol properly. You may need to raise the charge just a bit from starting to insure enough "oommph" to work the action, especially with a new weapon.
Once the COL is establised stay with this lenght and work up your load.

I load them to just feed through the mag. Or if you have factory ammo of the same bullet weight uwe that lenght.

go by the oal your loading manual suggests... i have a 9mm cartrage assembled without powder or primer and set at the perfect seating depth for the bullets i use... i use it for a gauge to set the seating stem on my die.....


LIFE IS SHORT.......