Today we tried tweaking loads with WW760 powder and the 57 grain and 78 grain spitzers. We also tried a new 46 grain spitzer.
All of today's loads used oven treated wheelweight, nose-sized, lubed with Rooster HVR, and a CCI #41 primer. The 46 and 57 grain bullets were sized 0.246", but the 79 grain bullet was sized 0.245".
Quickload believes this 46 grain spitzer requires a mere 22,000 psi to hit 2700 fps when pushed by WW760.

-- 27 gr. IMR4350
-- 2.180" COL (jam fit)
-- 2498 fps
-- 2.01% velocity standard deviation
-- 11 shots in 4.38"
-- 27.5 WW760
-- 2.171" COL (deeper than before, but still making contact)
-- 2683 fps
-- 1.13% velocity standard deviation
-- 10 shots in 2.5"
-- 27.7 WW760
-- 2.160" COL (0.003" away from contact)
-- 2757 fps
-- 0.82% velocity standard deviation
-- 11 shots in 3.75"
Conclusions about the 46 grainer:
-- doesn't seem to be a tackdriver
-- WW760 better than IMR4350
-- accuracy best with slight jam fit
-- barrel was clean other than powder fouling.
The same 57 grain spitzer that has been used previously. Quickload believes this bullet requires 25,000 psi to hit 2700 fps when pushed by WW760.

-- 27.5 WW760
-- 2.270" COL (0.010" away from contact)
-- flash hole drilled out to 3/32"
-- 2686 fps
-- 0.99% velocity standard deviation
-- 11 shots in 2.5"
-- 27.7 WW760
-- 2.265" COL (0.015" away from contact)
-- flash hole drilled out to 3/32"
-- 2658 fps
-- 1.04% velocity standard deviation
-- 11 shots in 5.25"
-- 27.7 WW760
-- 2.265" COL (0.015" away from contact)
-- 2681 fps
-- 0.69% velocity standard deviation
-- 10 shots in 3.6"
-- 27.7 WW760
-- 2.275" COL (right at contact)
-- 2661 fps
-- 0.91% velocity standard deviation
-- 10 shots in 5.6"
Conclusions about 57 grainer:
-- no obvious improvement with 3/32" flash hole
-- best accuracy seems to be 0.010" away from contact
-- barrel was clean other than powder fouling.
The same 78 grain spitzer that has been used previously, except nose-sized and loaded Ardito-style, with only the gas check in the neck. The front band engraved the rifling ever so lightly. By the way, sometimes I may call this bullet 77 grains or 79 grains -- it varies depending on the exact batch of alloy I am using at the time.
Quickload believes that this bullet requires 34,500 psi to hit 2700 fps when pushed by WW760.

Note that I determine the jam fit point by poking a bullet into the throat with finger pressure, and using calipers to measure from the base of the bullet to the breach (very easy to do on a Contender). With this bullet, finger pressure was enough to engrave the front band ever-so-ligthly. That created problems as discussed below.
-- 27.7 gr. WW760
-- 2.451" COL (0.013" away from jam but lightly engraving front band)
-- 2623 fps
-- 0.56% velocity standard deviation
-- 10 shots in 2.1"
-- but 9 out of 10 shots popped the action open, suggesting the cartridge was engraving too hard.
-- 28 gr. WW760
-- 2.440" COL (deeper than before but still lightly engraving front band)
-- 2609 fps
-- 1.09% velocity standard deviation
-- 11 shots in 2.1"
-- but every shot popped the action open, so it was still engraving too hard.
-- 28 gr. WW760
-- 2.420" COL (deeper than before but still lightly engraving front band)
-- 2675 fps
-- 0.76% velocity standard deviation
-- 11 shots in 4.7"
-- 2 shots popped the action open, so it was still engraving too hard.
-- 28 gr. WW760
-- 2.400" COL (deeper than before)
-- 2639 fps
-- 1.04% velocity standard deviation
-- 11 shots in 2.95"
-- but every shot popped the action open, so it was still engraving too hard.
Conclusions on nose-sized 78 grainer with WW760:
-- this bullet had shot patterns with WC844 but shows potential with WW760.
-- gotta change the front band diameter so that it is a slip fit rather than an engraving fit
-- it may be that it needs to engrave in order to be accurate, but that just doesn't work in a Contender.
-- barrel was clean other than powder fouling.
All of today's results. No bragging groups, but no patterns, either.
The chrono worked perfectly until the very last string, when it missed a couple of shots and then the display went blank. Troubleshooting revealed that a rat had gnawed on the power supply wires, grrrr.

I bet that was the root cause of the intermittent chrono problems I've experienced in the past few weeks?
Lessons Learned Today:
-- Previously I had assumed that the key to high velocity accuracy in this barrel was keeping the pressure low -- using light bullets and slow powder. But today I did not see a correlation between pressure and accuracy. All bullets shoot 2" - 5" when loaded Ardito-style and pushed by WW760. So it seems like the key is WW760 and the Ardito-style loading technique, not pressure. I don't know why WW760 is so much better than the other powders, but it was also my best powder in 30-06 hi-vel loads.
-- leading does not seem to be a problem in this barrel at 2700 fps.
-- all loads are darned sensitive to seating depth. Whereas 1-diameter bullets usually did best 0.015" away from contact, the Ardito-style loads seem to prefer contact. Unfortunately, Contenders won't lock the action reliably with a jam fit, so I have to err on the side of reliable chambering.
-- So far I have seen no clear advantage between sizing 0.245" vs. 0.246".
-- No clear advantage between the 3/32" flash holes vs. the standard flash holes, so I will stick with the standard.
-- the primer pockets on these cases haven't been cleaned since the 1980's

, and it was tough to seat the primers fully, effectively increasing the COL on some cartridges.
Things to Try Next Time:
-- make the 79 grain front band a slip fit rather than an engraving fit.
-- try a fatter M-die spud such that the bullet can self-seat when the action closes, instead of causing the action to pop open. Currently my homemade M-die spud leaves the neck ID 0.2415", try 0.243" or 0.244" instead.
-- clean the primer pockets.
