Complex sentence: This has the effect of lightening the bullet's forward section and shifting the center of mass towards the tail of the bullet, to give an improved ballistic coefficient, greater down-range velocity retention, and greater resistance to by crosswinds.
Split into simpler sentences: This has the effect of lightening the bullet's forward section and shifting the center of mass towards the tail of the bullet, to give an improved ballistic coefficient. An improved ballistic coefficient would yield greater down-range velocity retention and greater resistance to by crosswinds.