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Old February 16, 2013, 09:26 AM   #1
BlackSheep
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.308

What has the flattest trajectory at 1000 yds and still push through paper for competition shoot?
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Old February 16, 2013, 11:30 AM   #2
Jim Watson
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Flat trajectory is meaningless at 1000 yards, you must know the range and set sights for it.

The thing to look for is high ballistic coefficient and minimum wind drift.
Plug load data into your favorite ballistic program and see which is blown around the least. Hint, long range shooters are leaning towards heavier bullets than used to be considered standard. I thought a 175 gr .308 Win was a lot when I was shooting F-T/R regularly, but there are plenty of 185-208 gr bullets in use now.
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Old February 16, 2013, 03:08 PM   #3
JD0x0
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Well the flattest .308 is going to be whatever pushes the heaviest boat tail fastest. Not that flatness matters too much at 1000yrds.

You mainly want the highest BC possible to minimize drift and energy loss
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Old February 16, 2013, 03:17 PM   #4
Bart B.
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People have been shooting bullets from .308 Win. cases winning 1000 yard matches and setting records with weights from 147 to 250 grains. You'll probably have the flattest trajectory with a 155-gr. bullet leaving at 3100 fps from a 32 inch barrel that will drop 280 inches at 1000 and have a wind drift for a 10 mph cross wind's 86 inches. A 240-gr. bullet can leave at 2200 fps and drop 480 inches at 1000 yards but has a 10 mph wind drift of 81 inches.

Lighter ones have less recoil and are therefore easier to shoot accurately. But the heavier ones can have less wind drift if shot fast enough. Most top competitors will pick the most accurate, easy to shoot well bullet over the one that bucks the wind the best. But a flatter trajectory does not mean better accuracy. All match bullet weights shoot the same accuracy wise from properly built and fed .308 Win. rifles regardless of their weight

Pick one. Then get the right twist, barrel length and chamber size for it, load up some ammo and go put a smile on your face out performing others who don't start off on the right foot.
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Old February 16, 2013, 05:20 PM   #5
JD0x0
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Ballistic Calculator says:
a 150gr boattail with a BC of .442 drifts 113.39 @ 1000yrds
a 240gr boatail with a BC of .7 drifts 81.15 @ 1000yrds

Both fired at velocities with comparable muzzle energy.

Shooting long range in the cold at sea level makes BC increasingly more important.
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Old February 19, 2013, 02:39 AM   #6
allaroundhunter
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Quote:
Well the flattest .308 is going to be whatever pushes the heaviest boat tail fastest. Not that flatness matters too much at 1000yrds.

You mainly want the highest BC possible to minimize drift and energy loss
Negative. The flattest trajectory will be a lighter bullet pushed at a faster muzzle velocity.

A 155 gr Lapua Scenar leaving a barrel at 2,950 fps will have a flatter trajectory than a 175 gr SMK going 2,650 fps.

The heavier bullet will usually buck the wind better, however.
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Old February 19, 2013, 05:49 AM   #7
Rainbow Demon
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Ballistic tip bullets show less drift on the charts than equivalent conventional bullets. Whether they have consistent accuracy at longer range I couldn't say.

A friend had great results using pull down M2 AP bullets, 168 gr steel core flat base.
The 7mm hardened steel core of these is boat tailed but the base has a copper alloy plug to center it in a flat base jacket. This reduced oscilation of base and nose to give better penetration and prevented core breakup when striking amor plate at an angle.
The longer bullet for its weight and diameter seems to give excellent long range results.
Don't know of any similar civilian bullet designs out there.

PS
Due to some matchgrade ammunition being loaded extra hot to maintain supersonic speeds further downrange the British NRA instituted newer inspection methods for rifles to be entered in long range matches.

Last edited by Rainbow Demon; February 19, 2013 at 05:58 AM.
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Old February 19, 2013, 03:31 PM   #8
kraigwy
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Load a 175 SMK to 2600 fps and you're good to go.

Its the standard for M118LR (the Army's 308 sniper round), works great in a M1A (or mine anyway) and bolt guns.
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