Seems to me a bullet that shoots well at 300 yards in a OEM rifle IS obturating. It seems to me the Parker BE or E-MAX jacket is tougher than a copper clad Powerbelt and would be even harder to obturate into the rifling.

Both have cores made from fairly soft lead. Ive shot some great 100 yard groups with 300gr 45cal PowerBelt Plats but they fell short in terms of holding together.