Are you verifying that the holder goes all the way in and all the way down on the 2 pins?
Also, the holder can be mounted reversed.
Are the holes that the pins move in clean and not binding the pins?
Not questioning your experience, just beginning at the beginning.
If you have calipers, measure the rim thickness of your rounds and see if you might have out of spec
rim thickness.

If everything mentioned above checks out ok, I would call RCBS customer service, they are outstanding to work with and will go out of their way to honor their warranty if you have defective parts.

good luck
Covey16

The cases with .049 rim fit fine (25-06, 30-06 etc.) the cases with the .054 don't fit, there to tight. (.308, 260)
Do I have to adjust the pins every time I change rim thickness?
When I open the pins that hold the shell holder to fit the fatter rim, than the others spin.

On the RCBS trimmer I had, you pushed down on the lever and the pins extended.
The shell holder had 2 holes that tapered upwards.
You placed the shell holder all the way onto the extended pins and pushed down on the holder until the tapered portion of the holes in the holder slipped down into the grooves on the pins.
Release lever.
Press lever again, slip rim of cartridge down into the shellholder and release lever.
Spring tension should hold the case firmly and allow for a certain amount of variation in rim thickness.

If that doesn't work, either the shell holder is backwards or something is out of spec on the trimmer. JMO

good luck

Covey16

Sorry I did not reply sooner-The washers (springs) were installed incorrectly. The screw that holds down the head was very loose that it fell out. The pins that hold the shell holder were not screwed in all the way. After making the appropriate adjustments the cutter works great.
I called R.C.B.S. and told them that there product is good BUT there quality controll needs improvement.