I got out to the range this afternon to try a new load in my 257 AI. The bullet is a 90gr Sierra BTHP Gameking on top of IMR 4320.
The first pic is of the first 5 rounds. This load was with 46.0gr of powder and the average velocity was 3301fps. This was the most consistant load speed wise with a spread of 23fps. But, it measured 1.89"
This pic is of the next 5 rounds with 47.0gr of powder. The average speed was 3454fps with a spread of 75fps.
It measures 1.26". Better but I know that both the rifle and I are capable of better. Maby if I play with seating depth I might shave a little off that but I won't be happy unless I get it under an inch.
With the next 5 things start to go down hill in a hurry. This is with 48.0gr of powder. Our average speed is 3452 with a spread of 72fps.
One more grain of powder and the same speed? The worst thing is that this group measures 1.487" verticly by 2.840" horizontally!
To say that I'm not impressed at this point would be an understatement.
This brings us to our last group of 5. By this time some clouds had moved in and it was too dark for the chronograph so I was unable to get the speeds but by looking at the group it's pretty irrelevant as I won't be tryign this load again anyway. Can you say horizontal stringing? Sure. I knew that you could. This group measures 2.75" horizontal by .94" vertical.
If I can consistantly get the 47.0gr load to group an inch or less with that kind of speed I'll be happy. I don't know how much I can shave off, if any, by toying with the seating depth. Also it's been a little while since I've been out but I don't think that I'm that out of practice. Any hints or insight that you guys have would be greatly appreciated.
new 257 AI load
Threaded Mode
