This paper presents results from an extensive laboratory program of pullout testing of steel reinforcements used for Mechanically Stabilized Earth (MSE) walls constructed in Texas. Results focus on evaluation of pullout resistance factors for sandy backfill and MSE reinforcement combinations used by the Texas Department of Transportation (TxDOT). A unique aspect of this study is that this project uses Texas Tech University's large-scale MSE Test Box, one of the largest such devices in the world, with dimensions of 3.7m x by 3.7m x 1.2m (12ft x 12ft x 4ft) and an applied overburden capacity of 12.2m (40ft) of backfill. This test box facilitates pullout testing at a scale not unlike typical field construction. Results consist of pullout resistance factors for both ribbed strip and welded grid reinforcements for a variety of test variables including overburden pressure, reinforcement length, level of compaction, grid wire size, and grid geometry. We evaluate the data within the context of published AASHTO design guidance for inextensible MSE reinforcements.