Nitro; RE: Polychokes, we've had a few over the years and unless looks is the thing...which on a Mossberg is a ship that's passed as you know...I'd keep the Polychoke. I've had VERY good results with them, and the neat thing is they allow tinkering with the choking to get exactly the pattern you want.

Ignore the markings on the Polychoke body, and with your selected shot charges, start patterning, then just remember or jot down what the marking is for the load and desired pattern. Sometimes the performance is NOT what the marking indicates, which, actually, is true about screw-in tubes, also.

With slugs we just opened it all the way up which I THINK is the proper solution. IIRC, back in the '70's, slugs were said to be a no-no with a Polychoke, then that was wholly debunked and merely cranking the thing to CYL makes it all safe.

If I can find a cheap Ithaca barrel for my old 87, I want to cut it to 18 and have a soupcan installed. I really like them. With the screw-in tube barrel, I always seem to forget to install the right tube, and then compound the problem by forgetting to bring the spares...

Anyway, just another thought/option.