Gents,
I'll second Ross Seyfried. I've always liked his writing style, and talk about a broad knowledge base. If it goes "bang", he probably has experience with it. And he's got some serious bona fides...Africa PH...IPSC...
Warren Page was another one who could wield a pen as good as he could a rifle.
Although not considered a gun writer per se, Dave Brennan, the editor for the now defunct Precision Shooting magazine, used to write some stuff for the magazine about the early days of bench rest, and the equipment used. I always liked reading his writings.
I'm relatively new to shotguns, and so far, I'm really enjoying McIntosh's stuff.
Justin