Compare the BC of the 458 250gr Monoflex and a 458 325gr FTX. The are nearly identical in size and shape. The MonoFlex is guilding metal. The FTX is your standard cup and core. Both have a polytip.

The Monoflex is FAR less in BC. Roughly .175 vs around .230 for the FTX. Even the Barnes 458 300gr SOCOM boat tail is nothing to write home about in BC. Its pretty poor actually compared to a similar weight Parker BE. Its down right bad compared to a Parker Match Hunter.