I was able to try some 33.8gn .25cal Western pellets and tested a few groups in friends' back yard.
We measured their weight, out of roughly 30 pellets 95% of them are 33.7gn and 33.8gn, even split, with exception of 2, are 33.9gn. Standard deviation 0.14 gn, very tight. We didn't measure the whole tin, it became obvious that we won't find any wild spread. They look good, clean, thick skirt, dish base, dark grey.
Brought my Impact M4 with 600mm liner. Outdoor condition, 42 yard, light wind, tested velocity from 865 fps to 923 fps. All groups are less than 1/2 inch CTC. Longer range test would be nice but we were limited by the fence.
The 865fps group has 12 shots in the hole. The rest of groups are 5 shots each. Lower right group has a flyer caused by operator, me. Interestingly, the best group is 923fps. I didn't think pellets like high speed, guess I was wrong.
These pellets hits hard, and accurate, their heavier weight is good for windy days. Most importantly, it allows me to shoot heavier lead without going to .30cal. Will definitely stock up.