A quick search on google revealed:

  http://www.mcdougallittell.com/lit/sts/1299/sts1227.htm
    and
  http://www.mcdougallittell.com/lit/sts/1299/sts1227a.htm

And I quote:

  Idiom        lead with one's chin
  Definition   Take a risk, behave without caution
  Etymology    This term alludes to a boxer leaving his chin, a vulnerable
               point, unprotected.

HTH,
Ted

Thus it was written in the epistle of Gary Sielaff,
> I have heard that phrase but I am at a lose as to
> what it really means.  Please explain??
> Curious in Moses Lake
> Gary
> ----- Original Message -----
> From: Graham, Robert <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, June 20, 2000 3:19 PM
> Subject: Re: [HP3000-L] AS400
>
>
> > > From: Gary Sielaff
> > >
> > > I know.. I know .. An AS400 is an IBM mini.... Right???
> > > So, does it have any value?
> >
> >
> > Boy, talk about leading with one's chin!!!  :-)))
> >
> >
> > bob graham

--
Ted Ashton ([log in to unmask]), Info Sys, Southern Adventist University
          ==========================================================
When asked what it was like to set about proving something, the
mathematician likened proving a theorem to seeing the peak of a mountain and
trying to climb to the top. One establishes a base camp and begins scaling
the mountain's sheer face, encountering obstacles at every turn, often
retracing one's steps and struggling every foot of the journey. Finally when
the top is reached, one stands examining the peak, taking in the view of the
surrounding countrysideand then noting the automobile road up the other
side!
                        -- Kleinhenz, Robert J.
          ==========================================================
         Deep thoughts to be found at http://www.southern.edu/~ashted