Quoted:
Try 25.0 grains with the Sierra 69 grain bullet.
I'm a little surprised at the vertical stringing with 25.3 grains. Maybe try shooting a series again starting with a maximum load, then working down so you're shooting when you're not tired. 25.3 grains should be showing some pretty high pressure signs, too.
Aero,
I was very surprised by the results as well. After seeing the first two groups, I thought the heavier loads would really put a smile on my face. And you are right, my eyes (and elbow) were getting tired by the time I started the 25.3 group. What really surprised me the most was the velocity of the last group. Based on my 5th edition Sierra reloading guide, I was trying to duplicate their 25.3 load. The chart shows 2750, so I was thinking I would land somewhere between 2750 and 2800. I was really surprised to see almost every shot above 2900. Now I'm glad I stayed away from the 25.7 max load (which shows 2800 fps in the chart).
I'll start out next time at 25.0 grains and work down to 24.0.