I'll second that motion.Johnme,
Your getting there, but --------------
Now that you have shot, 25, 27, 29 and 31gr, and apparently with no pressure or safety issues, you need to go back and shoot 25.5, 26, 26.5, 27, 27.5 and 28gr.
You have some huge gaps in your testing data and many times, 1/2 of a grain makes a huge difference in group size.
If indeed 27gr does again show to be the apparent "sweet" spot, be sure and re-test those loads a number of times and best, 1/2gr. above and below.
I have a good number of test targets on hand, some of which show nice groups, worthy of retesting, and MANY times that load never again shot as well as it did on that first target.
Your well on your way, just close the gaps in your data and let us know the results.
Crusty Deary Ol'Coot
These numbers are certainly over Lyman 47, which is the last data I have located for this bullet and powder combination. I would guess your pressures are in the Ruger area for sure...I shot 25gr, 27gr, 29, and 31gr. with 2400 off the bench yesterday and the 27 gr. grouped the best. All I shoot is 405 gr. cast.