Complex sentence: The gun was a firm favourite among shooters in the 1970s and 1980s and it's considered by some to be a scaled down BSA Meteor Air Rifle, although this isn't the case.
Split into simpler sentences: The gun was a firm favourite among shooters in the 1970s and 1980s. It is considered by some to be a scaled down BSA Meteor Air Rifle, although this isn't the case.