What is the bore size of Warburton mouthpieces? Print
#27 is the standard bore size of Warburton trumpet mouthpieces. The designation corresponds to standard drill bit sizes, with the size increasing as the number decreases. #27 (.144") has long been the standard of the industry and has proven to be a good choice for most players, but there are cases in which opening the bore size does make sense,

If you are experiencing a "bottle-neck" or stuffy feeling, it is necessary to first consider other factors which may be the root cause such as:
  • Rim diameter too small.
  • Wrong backbore choice for you. What does the backbore do?
  • Wrong cup depth or style for you.
  • Too large of a gap.
If you have fine-tuned to your preferred resistance via the backbore system only to result in a sound which is just too dark or unfocused, a larger bore size may be in order. Opening the bore size will increase the maximum flow of air per second that the mouthpiece can accommodate without significantly changing its characteristic sound. If you choose to do this, have it done on a lathe by a qualified repairman or at the Warburton factory. You will need to alter both top and backbore. Remember, there is some risk involved, so never open the bore size by more than one step at a time.