SO, the question is, where do I look for a cause and how to fix it. I have not dropped pin gauges into the barrel or cylinder yet.
I pulled the old 44 mag SBH long barreled silhouette gun out of the safe this past weekend. First time it's been shot in 20 years. I saw a distinct pattern develop as I checked targets. It was really windy so I wasn't concerned with the horizontal stringing, but two of six shots were consistently low and the pattern was consistent at 25, 50, and 100 yards. I don't recall if I noticed this 25 years ago when I shot steel.
Had some fairly heavy lead in the forcing cone and first two inches of the barrel. From what I remember this was normal for this pistol as none of the old timers I shot with back in the day knew or cared to share the "voodoo" required to make a revolver shoot without leading up. I'm deciding what to do with this pistol. The front sight is off by several degrees so it will either need to go back to Ruger, or out to a competent revolver-smith to properly time the front sight to 12 o'clock. I didn't mind it when I shot IHMSA as it allowed for a natural hand\arm angle in creedmoore and I just paid attention to it when shooting off my hind legs. Now, it kinda annoys me so I want it fixed. I mention this because it will have to be corrected prior to any kind of fire lapping, and the correction may preclude firelapping.
FWIW the loads were all with components purchased in the 1990's. the WW296 was an unopened can from 1992:
240gr PENN cast SWC .430".
8.5 gr Unique
CCI 350
220gr Sierrra FPJ
24gr WW296
CCI 350
220gr Sierra 25 yds (this is a 6 shot group)
240gr Penn 50 yds
240gr Penn 100 yds