An extended-range Single-Particle Soot Photometer (SP2) coupled to a Marin-5 nebulizer was used to measure the refractory black carbon (rBC) mass and number size distributions in 1004 samples from a West Antarctica snow/firn core. The SP2 was calibrated using Aquadag and a Centrifugal Particle Mass Analyzer for BC particles ranging from 0.5 to 800 fg. Our results from 1.03 x 10 particles indicate a significant contribution of rare, large particles of mass-equivalent diameter (D) > 500 nm to the total rBC mass (36%), while small particles (D < 100 nm) are abundant but contribute < 8% to total rBC mass. We observed a mass median diameter (MMD) of 160 nm, smaller than reported for snow comparing to other regions of the globe, but similar to East Antarctica rBC size distributions. In addition, we observed a secondary mode at 1880 nm, possibly originated from a combination of rBC aging processes in the atmosphere and particle agglomeration during snow formation/deposition. We compared two sets of samples from different seasons (wet vs. dry), and observed different contributions of large particles to the total rBC mass of each. Particles with D > 500 nm contributed 45% and 33% of the total rBC mass for the wet and dry season, respectively, indicating that larger particles are more common during the wet season. Post-depositional processes (millimeter thick melt layers) have been observed in some samples, although they did not change the observed median diameter. This study provides the first detailed rBC size distribution from West Antarctica.