.308 Win

[mitchell koster]

Would i get a .308 to shoot flatter if i lowered the bullet weight and upped the powder in the shell? I'm new to reloading.
THanks MK

[hammie]

In general, yes. The actual result can vary widely with bullet type (round nose or spire point) and by manufacturer (depending on manufacturer's ogive) within the same bullet weight. Even seemingly same bullet designs can vary in their ballistic coefficients (for example: a plain spire point, a spire point boat tail or a sharp plastic tipped spire point). To make sure we are comparing oranges here, the following data was extracted from a hornady manual for hornady's plain spire point bullet. The velocities are typical maximum for a .308 and give the trajectory rise and drop in inches for a 200 yard zero.

weight bc vel, 50 yd 100 yd, 200 yd, 300 yd, 400 yd,
110 .256 3200, +.5, +1.4, 0.0, -7.2, -22.0
130 .295 3000, +.6, +1.7, 0.0, -7.8, -23.5
150 .338 2700, +1.0, +2.2, 0.0, -9.4, -28.0
165 .387 2600, +1.1, +2.3, 0.0, -9.8, -28.6
180 .425 2400, +1.5 , +2.8, 0.0, -11.4, -33.0

[Legionnaire]

Hammie is right ... out to mid-range. Beyond 800 yards, though, the lighter bullets run out of steam whereas heavier bullets (with higher ballistic coefficients) will carry farther before going subsonic. So "flatter" needs to be defined over a predetermined distance. But again, you are generally correct that, say out to 500 yards, a lighter, faster bullet will also drop less.

[Head-Space]

Yeah but --

Heavier bullets buck the wind better, and sustain velocity over distance. .308 Win. loads, for rule of thumb, for the "longer" shots -- 300 / 500 metres -- prefer a 165 / 172 gr. boat-tail. That's what the Dept. of Defense uses in .308 for the snipers.

If you're shooting smaller game (deer) at less than 300 metres, a 150 gr. bullet works. If you're shooting elk, moose, bear, you want a heavier bullet, 180 gr. or more. But you need the rifling to stabilize a heavy bullet, and you're going to limit range in the .308 Win. with this sort of bullet weight.

So it comes down to "balance." The right load for the application. Sort of like picking out a girlfriend.

[srsmith]

Some of the successful long range 308 competitors are now using Lapua 155gr Scenars at about 2900 fps.
It is a very long bullet wiith a BC of just over 0.500.

http://www.bigamericanman.com/blog/gun-stuff/

-steve

[Unclenick]

That's correct. And the new 155 grain Palma MatchKing redesign by Sierra (#2156, superseding the #2155 which is still made but no longer carries the "Palma" title) that competes with the Scenar has the same high BC and has also been winning 1000 yard matches. The BC is all that matters for being blown by the wind. Weight is already taken into account when BC is figured. The advantage a heavy bullet has over a lighter bullet with the same BC that is fired at the same velocity is not wind, but that it carries more kinetic energy and momentum to any given distance. That is why a 175 grain .308 is better at 1000 yards for sniping than a 90 grain .224 VLD with the same BC.

The business of flat shooting often gets overblown for most practical purposes. People forget that you zero the sights. That means the bullet first arcs up out of the muzzle then falls back to the zero range target center. That up and down path eats up a lot of the drop difference, and only the drop beyond the zero POI that starts to demonstrate the difference in flatness.

For example, the .30-30 running a bit warm from a modern gun might get a flat nose 170 grain Sierra bullet up to 2300 fps. The BC is only .201. At 200 yards, the bullet drop is 16.4". Let's compare that to a .300 RUM driving a 170 grain Lapua FMJBT with BC of .501 to 3000 fps, which has a total drop at 200 yards of 8.5". Almost twice as flat. But now zero both those guns at 200 yards and see how far the projectiles will both stay within an 8" kill zone circle centered at the zero range? Both stay within the circle to the zero point. The .30-30 then gets to 234 yards before the bullet drops -4" below the 200 yard POI. The .300 RUM gets to 270 yards before it drops -4" below the 200 yard POI. So the RUM gets you an extra 36 yards before you have to start holding over.

The amount you hold over at 300 yards will be quite different. 1/2 a foot for the RUM, and 1 1/2 feet for the .30-30. The .300 RUM will hit harder, and it only goes 1.5" high at apogee, verses 4" high for the .30-30. So, I am certainly not saying these rounds are equivalent. I'm just pointing out that difference in flatness at many practical ranges are not nearly as significant as the manufacturers would have you think. And most people don't choose between a .30-30 and .300 RUM, anyway. More likely they are looking at .300 Win Mag verses .300 RUM, or .30-30 verses moving up in power to the .308. When the differences between the rounds under consideration are not as extreme as my .30-30 to .300 RUM comparison, the flatness for a given zero makes a smaller difference in range beyond the zero, and there will be a smaller difference in holdover beyond it.