I' ve got an undertaker in one of my 1300 black shadows. Have used it in both guns with 26" barrels and have had identical results. It likes #6 shot. Whether it' s federal or Winchester, 2 3/4" or 3" , a heavey payload or the lighter HV loads. In my guns it shot #5 shot ok. But the set up really liked the #6 shot. Your results may vary.

No problem with the threads either. Homer J must have got a bad one. I' ve heard the same thing happening with other choke brands as well.

Good Luck!