I used to wonder why everyone mounted their pistol scope so far back. Now that I have used a pistol scope for the first time in my life, that question has been answered -- because the eye relief was designed for a midget! From the point of view of weight balance I would prefer to mount the scope centered over the barrel, however, eye relief takes priority over weight balance, so I moved the scope as far back as practical.
I rearranged the bench setup in search of something more comfortable. Because I am shooting through a narrow tunnel, I do not have the luxury of moving to a more comfortable spot. As it turned out, this setup was an improvement over last time, but still uncomfortable and still unsteady, so I'll have to continue trying different bench setups.
Last time plain base bullets leaded the barrel, so today I tried coated plain base bullets. I debated whether to quench the coated bullets. When I experimented with coated PB rifle bullets, I found that they were very fussy about BHN, with a sweet spot between 11 and 14 BHN. Anything softer or anything harder hurt accuracy a lot. So I decided to go with the same BHN for today's revolver bullets, letting them air cool after baking. However, it's certainly possible that coated revolver bullets may play by different rules than coated rifle bullets.
Also I decided that for the time being I will try to adhere to the 35,000 psi SAAMI spec, that way anyone following this thread can feel comfortable with the loads that I post.
Rather than seat the bullets to their crimp groove, I seated to 1.610" COL, leaving 0.010" clearance in the 1.620" long cylinder. The M29-357 does not kick hard so a crimp is not absolutely necessary other than to aid ignition. A charge of WC297 was chosen that would hit 32 - 33 Ksi if you believe Quickload. Quickload predicted 1500 fps from an 8" barrel (it is my habit to omit the cylinder length in Quickload and that seems to compensate for the velocity lost due to the barrel-cylinder gap) and the chrono said 1500 - 1520, so that gave me a warm fuzzy feeling about the pressure estimate.
Today's coated PB averaged 6.0" vs. 5.5" for yesterday's uncoated PB. While I did not shoot enough groups to "prove" anything, strictly speaking, there's no reason to believe that the coated bullets were more accurate, even though they did eliminate leading.
Nor is there any reason to believe that the PB Loverider bullet is more or less accurate than the PB TC design.
FYI the Loverider groups were shot with the scope at 8X, but I was struggling with the eye relief issue at 8X, so I switched to 6X to shoot the TC PB bullets. The eye relief was much more forgiving at 6X.
I felt like today's bench setup was slightly better than yesterday's, plus there was almost no wind today, nonetheless I still could not get comfortable. My uncomfortable bench technique is definitely adding at least 1 inch to the groups, maybe 2 inches.
-- Loverider load averaged 1512 fps
-- Loverider load averaged 69 fps six-shot ES
-- TC load average 1520 fps
-- TC load averaged 58 fps six-shot ES Things To Try Next Time and Down The Road:
-- retest the same loads except quenching the coated bullets.
-- keep trying different bench setups until I find something I have confidence in.
-- design bullets for this M29-357, with the crimp groove in the correct place, etc.. So far th M29-357 has not shown a strong preference for any particular design or weight, but there is much yet to try.