Checking Case Length:
Auto pistol cartridges headspace on the case mouth and not the case rim as revolver cartridges do. To make certain your cases are not too long, do the following:

1. Resize and deprime the case.
2. Drop the case inside the holes in our case gauge.
3. If your cases are flush with the top of the gauge, the cases do not need trimming. However, if they do protrude, then trimming may be required.

Checking Proper Bullet Seating Depth:
1. Install the bullet into a correct length case and drop it in to our gauge.
2. If the case is flush with the top of the gauge, the seating depth is correct (for that shape, style, length and weight bullet).
3. If the case protrudes slightly, remove the cartridge and reseat the bullet just a fraction of an inch deeper into the case and try again. If the case is still protruding, seat the bullet deeper and stop when the case sits flush with the gauge.
4. With the cartridge still in the gauge, hold it in place with your finger and turn the gauge over. The tip of the bullet should not protrude beyond the bottom of the gauge. If it does, the bullet is not seated deep enough and should be set deeper.
5. If the case has been properly resized, the length is correct, and the bullet is seated to the proper depth, you should be able to turn the gauge over and have your cartridge fall out by gravity alone.