The 930 Tactical already has a 18.5” barrel.
Back when, prior to Reagan, I bought an Eastfield 12 Ga pumpgun at a gun show down in Kankakee, Il, for $70.
A stop at the factory model shop, $10 to an old toolmaker, and he clamped the barrel and receiver into the lathe and parted off the barrel at 18.75, measured from a closed bolt. He brazed the front sight back on, mostly for show.
It was in my gun case for a few years, til my stoner brother pawned it for some pot...
Was it a 916? No idea. It worked like a charm, tho, action was slick and fast. Probably since I ran 200 rounds through it. I'm a believer in the fact that, like any other machine, it's best if the machine is worn in.
(Something you might consider when you get a new toy, and your fanny is going to depend on it...)