Originally Posted by TN Lone Wolf

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For my 270, I wanted to test the new IMR 4955 with 130 grain SST bullets. This is the Enduron powder closest in 4831 in performance, which is a powder I've had recommended to me quite often. I created nine groups of five loads ranging from 56 to 60 grains of powder in 0.5 grain increments. Sunday, I set about testing them.

In short, I was very disappointed. The majority of the groups were at least 3" across, even though I felt as though I did well on most of the shots. My two best groups came from 58.0 and 59.0 grains:
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That said, I was very happy with the velocity data I got. Using 58 grains of IMR 4955, I got an average velocity of 3142 fps with a standard deviation of 14, while 59 gave me an average of 3152 fps and 18 fps s.d. With that kind of consistency, I would expect a bit better accuracy.

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Thoughts?