WW748: a spike-friendly powder?
'Since WW748 powder seemed to alleviate the secondary spikes in a 7-30 carbine, it seemed worth trying in the 30-06, too. Since the last range session, my 20 year old can of 748 was used up and replaced by a new jug, so there may be some small differences in burning rate.
47.5 gr. WW748, 180 gr. cast loverin, 0.314" x 0.308", heat treated wheelweight, Rooster HVR lube, 2.965" COL, seated to engrave lightly.
10 rounds were loaded with WLRM primers, 5 with CCI #250.
5 shot groups at 100 yards
#1 (WLRM) = 2"
#2 (WLRM) = 4 shots in 2.5", 5th was flyer making 7.4" group
#3 (CCI250) = 2.25"
You guys who only shoot jacketed or low velocity cast may not be impressed with 2" groups, but this is as good as this rifle has ever done with full throttle cast loads. I'm delighted.
Velocities & pressures
#1 (WLRM) = 2572 fps, 94 ES
#2 (WLRM) = 2575 fps, 70 ES, 59.2 ksi
#3 (CCI250) = 2610 fps, 20 ES, 61.2 ksi
Here's the trace for WLRMs. Lots of shot-to-shot variation, but only moderate secondary spikes.
Here's the trace for CCI 250s. Very consistent traces and velocities -- so go figure why the group had vertical stringing. Maybe due to the differences in muzzle pressure ??????? I should add that there were large differences in seating effort. Some cartridges chambered effortlessly while I had to use my fist to hammer the bolt closed on others. That's a common problem with cast bullets that are seated to engrave, due to variations in diameter or due to lube build-up in the seating die.
I've never had good luck using 748 for jacketed bullets in any cartridge. 748 has been prone to vertical stringing and mediocre accuracy. But it seems to be the trick for getting rid of secondary spikes, and these low-spike loads were more accurate in this rifle than any other high velocity cast bullet load that I have tried. Coincidence?
Next time I'll drop the powder charge a bit, because today\'s pressures were too high. I'd like to try still more primers, and I need to work on getting a consistent degree of engraving.