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Nb3Sn strands extracted from a 20-strand rectangular Rutherford cable were reacted on either stainless steel or Ti-alloy barrels and the critical current, Ic , in the field range of 8-11.5 T was measured on ITER-type barrels made from Ti-6Al-4V alloy, 304 stainless steel and G-10. Measurements on the “standard” Ti-alloy barrel using the test procedure employed at BNL are shown to reproduce Ic for extracted strands to ±2%. The Ic data for the sample mounted on the “standard” Ti-alloy are fit to the deviatoric strain scaling model developed for Nb3Sn by the University of Twente group using an arbitrary pre-strain. Using the parameters for this fit, the Ic data for the other barrels are fitted by only adjusting the strain. Using this procedure, the strain difference due to the barrel material is determined. Assuming a thermal pre-strain of -0.2% for the sample measured on the Ti-alloy barrel, the use of stainless steel barrel increases the compressive strain by -0.07%, that of G-10 by -0.10%. With the wire soldered to the stainless steel barrel, the strain increases to -0.15%. Details of this study are presented.