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Old September 22, 2000, 11:35 PM   #1
Steve Smith
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I'l begin loading for .308 Win for my M1A soon. I'm wondering this: Is the most accurate load at 100 yds always the mostaccurate load at 600+? If not, what's the first thing I should start changing in my loads?
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Old September 23, 2000, 12:19 PM   #2
Zach Vonler
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Consistency is consistency, so the most accurate load at 100yds has the theoretical potential to be the most accurate at 600yds. However, the longer the distance the more the bullet will be affected by wind. Thus if you develop a load with a low ballistic coefficient and it shoots well at 100yds, it might actually be harder to get as good of accuracy out of it at longer ranges (because the more the bullet is affected by the wind, the more variance there will be in exactly how much it's affected). Thus if you're planning on long range it would be best to work up a load using a bullet with a high ballistic coefficient.
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Old September 24, 2000, 12:56 AM   #3
Cheapo
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A lot depends on what bullet you use and how far beyond 600 you want to go. When your bullet goes transsonic, it becomes VERY susceptible to wind drift and the dispersion no longer resembles a straight-sided cone. It flares out a lot.

Your 147-gr M80 pills go subsonic somewhere beyond 600 yards, IIRC. Sierra 168s go sub somewhere around 800. The Sierra 155 Palma will carry to 1,000 if you launch it at 2800 fps, while the 175 requires 2600.

Testing in the .30 calibers has shown that some good performers at 100 yards *can* puke at either 200 or 300. But if a load does well at 300, it will almost always hold up well until the bullet goes transsonic.

Don't use pulled M2 ball bullets. Besides having the crimp groove too far back for your 7.62 (OAL is too long if you use it), their flat base design makes them go subsonic BEFORE 600. I've pulled targets for people shooting M2 Ball at 600, and it was not a happy experience for anyone.
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Old September 25, 2000, 11:34 PM   #4
alan
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Frontsight:

What works well as 100 might not even hit the target at 600, for various reasons. The 300 yard dictum mentioned is usually sound.

Depending on what bullet you are going to use, and which brass, military match is good if available, try 4895 in the range of 39 to 42 grains, assuming a bullet weight not greater than 180 grains.

Slightly greater charges of 4064 would work, as would slightly lesser charges of 3031. I mention these powders, because I was personally familiar with them, especially 4895 and 3031. There are many others though. With a gas gun, you would likely be best off with propellants in the "medium" burning rate range. Try to duplicate the military loading, or come close to it.

If you could find a worth while quantity of FA Match Bullets, nominally 173 grain, .308" dia, though usually a little fatter and heavier, they often shot quite well in "service" rifles (gas guns). Otherwise, Sierra 180 and 168 grains Match King, and Hornady equivalent usually shot well too.

Hope the foregoing helps.
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Old September 26, 2000, 06:07 PM   #5
HankL
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Frontsight, NO But the most accurate at 600 yds. will most likely be the most accurate one at 100 yds. in the .308 as well as most regular calibers at least. While shooting matches it was a question of economics. 200 yard line = 147 gr. military ammo. The longer range slow fire stages = 168, 173, or 175 gr. quality projectiles.
600 yds. is quite a distance to use in working up a load but if you have a place where you can shoot 200, you can usually see the bullet holes in your target at this range, that would be a good place to start.
Sierra 168 gr hpbt Match, 41 gr. of IMR 4895 or 42 gr of IMR 4064 or W 748, using military brass and Fed. match primers would not be a shabby place to start.
Best of Luck
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Old September 26, 2000, 07:49 PM   #6
Steve Smith
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My range has a max of 200 yds at this time...sounds like I'd have to work on a load for that and then try a couple of other ranges. Thanks for the info, guys.
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