Can a 12 gauge Glenfield Model 778 shotgun be fitted with slug barrel?

The Glenfield Model 778 shotgun is not a firearm manufactured by Remington, but by Marlin. It is a pump-action shotgun that was introduced in 1968 and discontinued in 1981. The Model 778 is chambered for 20 gauge shells and has a 4-round magazine capacity.

No interchangeable barrels were offered for the 778.