  We report on an investigation of the LANL method for determining the O(a)
improvement coefficient c_A nonperturbatively. We find we are able to extract
reliable estimates for the coefficient using this method. However, our study of
systematic errors shows that for very accurate determinations of c_A, the
smearing function must be tuned and the volume fixed to keep the O(a) ambiguity
in c_A fixed as beta varies. Consistency was found with previous results from
the LANL group and (within fairly large errors) 1-loop perturbation theory; c_A
does not change significantly over the range beta=5.93-6.2. The big difference
between our results and those of the ALPHA collaboration, around beta=6.0, show
that the O(a) differences in c_A between the different methods can be large. We
find that the lattice spacing dependence of f_pi and the renormalised quark
mass is much smaller using our values of the coefficient compared to those of
the ALPHA collaboration.
