O*

Effective interactions derived from first principles used to describe elastic scattering of nucleons from nuclei can be formulated consistently within a multiple scattering theory based on the spectator expansion. In its leading order the NN force enters into the description of the nucleus as well as the reaction itself and is treated on the same footing in both. Employing a semilocal coordinate-space regularized chiral EFT NN force and corresponding one-body density matrix elements from the LENPIC collaboration, we study the truncation errors of the chiral expansion for proton elastic scattering observables from ¹⁶O for projectile energies between 100 and 200 MeV. Using a Bayesian truncation error model developed by the BUQEYE collaboration, we quantify these errors in the NA system for the first time while examining the reaction cross section, differential cross section, and analyzing power for this reaction.