meplat trimmer issue

[parker_chp]

I borrowed a tubbs 308 meplat trimmer from a friend and run in to the issue that it wont reach the meplat of the 175 smk's im trying to trim. He has used the trimmer before and had no issues. I loosened the set screw all the way and the cutter still wont reach the meplat with the screw in the flat spot. the directions just say to insert the bullet and adjust the bit to cut the desired amount. I have tried with loaded and unloaded bullets. any ideas besides moving the set screw out of the flat spot that helps keep it from slipping?