Trying some slightly different bullet designs. Based on the results of the water tank tests I eliminated the bore riding bands and put more and bigger grooves on the top half of the bullet.
First up, a 190 gr. GC. The 0.090" long crimp groove is overkill for crimping, but it is intended to also act as a "shock absorber" that gives displaced lead somewhere to go when the bullet slams into the forcing cone.
FYI I photoshopped today's target images to clean them up and make them easer to understand.
The 190's first group (top left) put 5 shots into 1.1". But a second group with the same load (top right) was ho-hum.
Switching to Federal 200 magnum pistol primers (bottom left) gave slightly slower velocity, about the same ES, and a ho-hum group.
Going back to CCI 550 primers and increasing the powder charge (bottom right) resulted in an uninspiring group.
The good news is that using CCI 550 primers and R-P cases seems to bring the ES down to a tolerable but still not great 52 ES, compared to the 70 - 80 ES I was getting with mixed brass and WSPM primers.
The Federal primers were OK but no better than the 550's.
Increasing the powder charge may hurt accuracy.
The three 15.9 gr. groups had mostly vertical dispersion despite decent ES, making me suspect that my grip and my benchrest technique may be to blame. I'm definitely rusty at wheelgunning and I'm still not that comfortable with my benchrest set up. Since adding the "cheater sled" the crosshairs look good when the gun goes bang, leaving consistent grip the remaining thing that needs improvement. It doesn't help that I have to release the gun between shots in order to type in chrono data. Perhaps once I am satisfied with a load's chrono results I should try shooting a group without releasing the gun between shots?
Next, a 180 gr. coated bevel base. This is nearly the same design as the 180 BB I have tested previously, the difference being adding the big-ass crimp groove and getting rid of the bore rider band.
The first group with the 180 was uninspiring, and I was running short on daylight, so I did not shoot more groups with the 180. But it's possible that I was to blame for the fliers, or it's possible that the powder charge may be a little too warm for a plain base bullet, even if it is coated. Next time I may try again with a lesser charge.
The good news is the ES was a decent 52 fps with R-P cases and CCI 550 primers.
Next, a revised 140 gr. GC, this time with the crimp groove stretched to 0.070", designed for seating out to 1.612", and no more bore riding band. There is no lube groove other than the check shank, and I wasn't sure if that would be enough lube, so I coated a few of these bullets as a fail-safe measure.
I am attracted to this bullet weight because Quickload thinks it can safely reach 1800 fps from a revolver -- that would make for an impressive "Whitetail Whacker."
I switched to WW296 for the 140 gr. bullet because I figured the faster burning powder would be more appropriate for the light bullet. But WW296 did not burn well -- velocity was well below the predicted 1800 fps, ES was high, and it produced a big ball of fire!
Nonetheless the coated version turned in middlin' accuracy, with 3 bullets touching -- it acted like it was trying to shoot despite the poor powder burn. My webcam software was acting up during that string so it only recorded 3 shots -- for what it was worth the 3 shots had a 56 fps spread.
The uncoated version made a bigger pattern, was 45 fps slower, and had 105 ES. A single group is rarely enough to prove anything, but I'm leaning toward the coated version of this bullet.
While 4 MOA will not win target matches, consider that it's minute-of-whitetail-heart and better than most of us can hold under field conditions.
Since WW296 did not burn well, I will make a note to retest the coated 140 with WC297 and perhaps with 2400.
In general, the revised designs turned in about the same 6-shot groups as their original designs, but at least the revised designs sometimes acted like they were trying to shoot if the guy behind the trigger would do his part. I'll try to follow up with load tweaks and water tank tests.