Smith told me a DX had to shoot 1 1/2 inch groups at 50 yds to qualify as a DX. If it didnt meet that it wasnt designated a DX. I
have several DX guns and they are great and I do have both a 5 inch 629 DX and the 5 inch 29 DX so they were made in that Bbl length. My understanding is the 5 inch DX was only made one year.