bercov@bevsun.bev.lbl.gov (John Bercovitz) (06/12/91)
The curved ogive of a secant-ogive bullet meets the body of a
bullet at a shallow angle rather than tangentially as is common
practice. This allows a very long radius ogive without giving up
the cylindrical section of the bullet which is needed for proper
guidance of the bullet in the bore. The secant ogive approaches
the long-cone nose-shape of an ideal projectile.
The above is what I speculated some time back in rec.guns.
I just received confirmation from one Charles R. Fagg, contributing
editor of the "American Rifleman", that my definition is correct.
Mr. Fagg had an interesting correction:
"Your assumption of the ideal shape for the front portion of
a bullet is, however, not quite correct. All other characteristics
of the bullet being equal and at typical center-fire rifle velocities,
a bullet with a secant ogive of large radius experiences less drag
than one with either a conical point or a tangent ogive of the same
length."
I found this very interesting because I've never heard from an
aerodynamicist anything except, "A conical point has the lowest drag."
A conical point is what you see on some military cannon shells and
many re-entry vehicles. Military cannon shells have roughly the
same velocities as rifle bullets but are much larger in diameter.
Re-entry vehicles are much larger and are hypersonic. It's easier
to make a conical point if you're machining up a nose but it's easier
to make tangential and secant ogives if you're forming up a nose.
What are the determinants here? What gives? Anyone know?
JHBercovitz@lbl.gov (John Bercovitz)