This paper presents the application of beam transmission modeling to the problem of large aperture transducer focusing in cylindrical billets. This work is to aid in the design and procurement of large aperture bi-cylindrically focused transducers for use in the multi-zone billet inspection system being developed under the FAA Engine Titanium Consortium (ETC) program. Need for this work arises from 1) errors due to diffraction and focusing aberrations which occur when established optical lens formulas are employed in the design of acoustic lenses, 2) focusing errors resulting from billet surface geometric irregularities which are not readily handled by other beam model approaches.