Thursday, September 27, 2007

Range day

Amazing how some things work when you have a fresh battery

Started out cool, humid and foggy. Clearing when I left the house, but the closer I got to the range the foggier it got. Happily, it cleared off shortly after I arrived. Unhappily, add bright sun and warming temps to that humidity and you get melting feelings by the end.

Main thing I wanted to do today was, since I had the aforementioned battery, set up the chronograph and find out what velocity I was getting with the .30 Carbine loads described here. Which information follows after this brief

DISCLAIMER

This load is not out of any loading manual: it's one I put together based on load information I read and comparing that to the bullet and powder combination I wanted to use. It works well(so far) in my rifle, it may not be safe or accurate or reliable in yours. You have been warned.

As I wrote before, I wanted to load for this cartridge with a bullet that would give better terminal performance* and hold velocity better as the range stretched out. After trying three different bullets I decided on the 110-grain Sierra Varminter. It's a nice spitzer shape, hollowpoint, and the same weight as the standard FMJ bullet. It's longer, so it has to be seated deeper into the case to reach maximum length for this cartridge. That leaves less room for the powder, so I dropped one full grain to try it. Functioned perfectly and gave good accuracy at 100 yards, but I had no way to guess at pressures due to the *!!#@)*#$ dead battery in my chrono last time I went out.

The load is 14.0 grains of W296 powder, CCI standard small rifle primer in Lake City cases. Max length for this cartridge is 1.680" according to the Lyman manual, I actually seated to 1.679", for what it's worth. I fired ten rounds in two groups of five with the chrono about ten feet in front of the muzzle, and got these velocities:

1913 1933
1926 1931
1925 1924
1930 1930
1922 1924

Average velocity works out to 1925.8, and according to the calculator I used that gives a standard deviation of 5.77, which is pretty small. That's very consistent velocity.

And since the standard velocity for ball ammo in this cartridge is 1900 fps, I'm guessing the pressure of this load is pretty close to the standard cartridge. The proper way would be to have a strain gauge to mount on the chamber or access to a test barrel, but I don't have either of those. So I'm going by velocity for a decent guess at pressure. Which is why the big DISCLAIMER up there.

So far, all's well. It cycles through the action no problem, empties eject roughly the same distance & direction as ball, and accuracy is good. So now I need to gather some milk cartons or something so I can shoot them & see how the bullet acts at this velocity. Be a pain to find out it's too low for consistent expansion, but if that's the case then this load isn't what I was looking for. According to the reviews at Midway on this bullet, one guy was getting very good results with it. So we'll see.

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