I was working the 100 yard line at our club's annual Deer Rifle Sight-In event yesterday. I had my 10.5" SBH .44 Mag with me as I intended to head to the pistol range later in the day to shoot it. It occurred to me that I had never tried shooting the SBH at 100 yards, so during the lunchtime lull, I broke out the gun, securely benchrested it on some sandbags, and proceeded to lob some of my usual "light magnum" target handloads (240 gr. JHP projectile with 19.5 gr. of WC820 powder at an OAL of 1.64") downrange.
Not knowing what the bullet drop would be at that distance, I "guesstimated" and aimed above the bullseye, about a quarter ways down from the top edge of the target sheet. The first shot landed 3" to the right of the bullseye; subsequent ones formed essentially a horizontal line level with the bullseye, but the shots seemed to be randomly going left and right, exhibiting a windage spread of nearly 15", with no adjustments to the rear sight blade.
Upon closer examination, I noticed that there was a small but noticeable amount of sideways play in the entire rear sight assembly, which I suspect was responsible for the windage variations. When I was cleaning the gun last night, I removed the assembly and put a few tiny drops of JB Weld on the left side of the pivoting arm, let them set, then filed them down with a fine jeweler's file until the rear sight assembly could fit into its slot on the top of the frame without any sideways play.
Hopefully, this will reduce the windage variations at 100 yards. I'll test this out on my next range outing later this week.