Yes Spanish guns were the ones used.I have one and it is branded Basque, but I believe the majority that made the base for conversion were Zabala and a few AyA Matadors.
The barrel bulging is due to the fact that the bores are right on (under?) the designated size for 8 bore and the uninformed used standard 8 bore plaswads which are a tad on the large size for these conversions.The majority were bulged in the left barrel due to the higher degree of choke.Hone out the choke to about modified or less and they seem to be okay.
