  Suzaku X-ray observations of the Type Ia supernova remnant (SNR) 3C 397
discovered exceptionally high mass ratios of Mn/Fe, Ni/Fe, and Cr/Fe,
consistent with a near $M_{\rm Ch}$ progenitor white dwarf (WD). The Suzaku
observations have established 3C 397 as our best candidate for a near-$M_{\rm
Ch}$ SNR Ia, and opened the way to address additional outstanding questions
about the origin and explosion mechanism of these transients. In particular,
subsequent XMM-Newton observations revealed an unusually clumpy distribution of
iron group elemental (IGE) abundances within the ejecta of 3C 397. In this
paper, we undertake a suite of two dimensional hydrodynamical models, varying
both the explosion mechanism -- either deflagration-to-detonation (DDT), or
pure deflagration -- WD progenitors, and WD progenitor metallicity, and analyze
their detailed nucleosynthetic abundances and associated clumping. We find that
pure deflagrations naturally give rise to clumpy distributions of neutronized
species concentrated towards the outer limb of the remnant, and confirm DDTs
have smoothly structured ejecta with a central concentration of neutronization.
Our findings indicate that 3C 397 was most likely a pure deflagration of a high
central density WD. We discuss a range of implications of these findings for
the broader SN Ia progenitor problem.
