Found it just doesn't like the HyTech coated Missouri Bullets as the barrel is leaded up after 10 rounds but they shoot well.
Also brought along my Ruger SBH with 7.5 inch barrel and after 12 rounds of MB coated bullets the barrel was perfectly clean.
My 69 shoots the 230 gr. gas checked lead bullets,from Matt's Bullets fine with no leading as well as the Xtreme bullets.
Cylinder throat diameter on both revolvers is the same size .4305-.431
Anyway enjoy the short video of shooting the MB coated bullets!
My M69 is now a very nice shooter!
YouTube