As I recall, this was a variant of the Mag 10 intended for "Serious" work. The bbl was 22", mag capacity was a mere 3.
All the Mag 10s has an unearned rep for being finicky. Usually, ammo selection cleared this up PDQ, tho some needed a bit of internal adjustments like the gas ports changed in size.
There were a couple reasons the Roadblocker didn't catch on.
One, it was expensive, a dept could buy two or three 870s for the price of a Mag 10. Ammo cost more more than LE style 12 gauge stuff also.
Two, most cops are not enthusiastic shooters, and even at 10 lbs, this piece got your attention at ignition.
Three, that ten lbs was a problem, since many cops these days are of small stature.
Four, special purpose ammo development was mostly limited to the 12 gauge, since that was the national standard gauge for LE.
Five, 3 rounds, even these howitzer rounds, was not enough in the eyes of most cops.
On the up side, these are good for turkey hunting and waterfowl, if the guys in the blind with you wear hearing protection.
Long ago, I got to try one of these for a coupla shots. Blast was intimidating,kick was heavy but tolerable to me, effect on the target was tremendous. IIRC, load was 18 00.
HTH...
