Need some load workup advice
I'm doing a workup for a 300wm and having some difficulties getting anywhere. I've done a full ladder test and can't seem to find anything that works. Hoping I can get a nudge in the right direction to get over this hump.
Fed 215m primers
Winchester Super-x cases, fireformed with full case prep (neck turn was only partial though, no bushing dies uses)
Remington 700 5r 26"bbl
Accurate powders lists 85.5 grains as the max (3146fps), and a starting load of 76.9. I did a pressure workup and found that I got much higher velocities than expected and stopped at 83.5 and 3210fps. I'm a little...confused I guess is the word...because that's 2 full grains short of listed max and over 60fps more. The cases show only a slight polishing of the extractor at that powder charge, with no extra bolt lift force. About one out of every 10 or so need a SLIGHT bit more aft pressure, but once the case moves there's no other resistance. No other pressure signs w/ case or primer
At this point I don't have enough experience to know whether it's normal to get that much deviation from listed data, or should I check into the chrony's accuracy and keep working higher. The Shooters Chrony seems fairly consistant, but prints about 50fps higher velocities on the Winchester factory rounds. Seems like a plausible velocity, though, considering the drops I've verified at a few different ranges are pretty close to what EXBAL shows.
After all that, I ran a ladder test from 678 yards. The target data doesn't show any well-defined "nodes" except a slight tightening around 81 grains and another at my max load of 83.5grains. The velocity data supported a tight node around 83-83.5 (3fps ES one day and 10fps ES another day), at around 3108fps, so I figured that one was my best bet, even though it's pushing max.
Today I set up four different loads, two near the middle "node" and two near the upper node...with five shots each. Just got back and don't have a single load showing any promise. All groups (from 400yards) are around 6" plus or minus. Then I put 5 of my go-to factory round, Winchester Super-X cheapies, into a 4.1" group, with only about an inch of horizontal spread. Grrrrrrr.....
I'm not sure where to turn next...different powder? Bullet? Primer? Should I call BS on the chrony? I've shot close to 100 rounds and wasted several DAYS with nothing to show....I guess I'm still hoping that there's still hope...If someone can lend some experience I'd sure appreciate it.