The stress effects in various multifilamentary Nb₃Sn superconductors have been investigated for a large scale, high field magnet. The experimental apparatus utilizes a 6T splitpair magnet with the sample in a straight geometry. The results show that at stresses above 250-800MPa the critical current is significantly degraded, with the magnitude of the reduction dependent on reinforcement techniques and construction in the conductor. The effects are related to mechanical properties, especially 0.2% yield strength and apparent Young's modulus of Nb₃Sn composites at 4.2K.