  We describe results of a high-statistics finite size scaling analysis of 4d
compact U(1) lattice gauge theory with Wilson action at the phase transition
point. Using a multicanonical hybrid Monte Carlo algorithm we generate data
samples with more than 150 tunneling events between the metastable states of
the system, on lattice sizes up to 18^4. We performed a first analysis within
the Borgs-Kotecky finite size scaling scheme. As a result, we report evidence
for a first-order phase transition with a plaquette energy gap, G=0.02667(20),
at a transition coupling, beta_T=1.011128(11).
