Should I change the nut? (BF#BE or CGCF tuning)

LSW

Guest
May 30, 2016
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I have a Warwick Fortress one 4st MIG 93.
And I'd like to put a 125(125-85-65-45) gauge string on the 4th.
Should I change the nut to make this tuning?
 
I'm guessing you're going from a .105 to a .125 4th string. You'd at the least have to file the slot to accommodate the larger string. While (from the photo) it looks possible to file the slot you may need a new nut.

Before doing anything take it to a luthier and ask.
 
Try putting on the string and just lowering the saddle. It probably won't fill the saddle perfectly, but since the nut is adjustable it might work anyway.
Using ABM 6250 on one of my basses. It doesn't need a perfect fit to be playable.
 
If the string sits in the slot properly you don't need to file anything. Have a look and see if the string is sitting right into the bottom of the slot. If the slot is too narrow there will be a gap under the string, in which case widening the slot is in order. Use a flashlight and a magnifying glass - you need to look closely.