I have a Topper Deluxe Classic in 20 gauge. What oneounceload said is normally true of H&R/NEF single shots, but my particular gun is a fairly solid 7.2 pounds. The reason is that the barrel is made from a 12 barrel blank. I know because I have a 12 gauge barrel for the gun too and the outer dimensions are identical. Since the 20 gauge is only bored out around .615" instead of .729" that leaves a thick, heavy barrel.
The gun comes with a modified screw-in choke, and uses common Invector (but not invector+) chokes. Mossberg accu-chokes, and Winchester Winchokes also work.