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Load Workup for the .338-06 with Light for Caliber Bullets
Old 12-09-2017, 08:59 PM
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Default Load Workup for the .338-06 with Light for Caliber Bullets

You can look here: http://thehunterslife.com/forums/showthread.php?t=19372 for where this got started.

Lehigh Defense has a bullet design they call the "Close Quarter". You can see lots of performance tests in ballistic gelatin on YouTube. Here's a place to start: https://www.youtube.com/watch?v=I1mQ...gHqK8lCxzZUriH

Since I like Light for Caliber (LfC) bullets, I ordered some of these CQs in .308 and .338. The .308 bullet weighs 79 grains nominally, and the .338 weighs 103 nominally. (The ones I have in my hands are just shy - 0.15 grains - of each of those values.) Since I have the bullets in hand, it's time to start working up loads. I decided to start with the .338-06.

As I mentioned in another thread, Lehigh Defense provides some interesting information on their bullets. One piece of valuable information is the maximum rotational value the bullet can handle without coming apart. As those of you that have followed my exploits with the .17 Predator (http://www.thehunterslife.com/forums...t=.17+Predator) know, I've had some issues with bullets coming apart when driven past about 4500 f/s in the .17 Predator. Given the 1:9 twist of the Predator's barrel, at ~4500 f/s, it's doing about 360000 revolutions per minute. So... I have some interest in knowing what a bullet manufacturer thinks is "too fast" for their bullet.

Given a 1:10 twist rate, a muzzle velocity of 3750 f/s will generate 270,000 rpms - the 'legal limit' for the 103-grain, Lehigh .338 Close Quarter bullet. I thought that would be 'no problem' in the .338-06, and it isn't... but... there are a couple of powders that get 'right up there'. According to QuickLOAD, BL-C(2) generates a MV of 3671 f/s at a max pressure of only 56,875 PSI in a 24-inch barrel. That MV with the 1:10 twist puts the bullet's rpms at 264,312. That's purty close to 270,000. About 2% close. And, that's using closely measured numbers for input into QL, that are specific to my rifle and the bullets I have in hand.

That 102.9-grain bullet doing 3672 f/s generates 3080 ft-lbs at the muzzle, (about the same as an '06 with 180-grain bullet doing 2775 f/s), but the .161 BC means it sheds both velocity and energy PDQ. At 100 yd, it has just over 3000 f/s velocity and just under 2100 ft-lb of kinetic energy. At 200 yards, the velocity has dropped to 2450 f/s and the energy to 1370 ft-lb.

Another "nice" piece of information that Lehigh provides for these bullets is the minimum impact velocity required to make their terminal performance be as-designed. For this bullet, that figure is 2350 f/s. Given the above QL load, and the manufacturer's ballistic coefficient of .161, when this bullet starts out at 3671 f/s, it's velocity drops to 2350 f/s at 220 yards. It's energy is 1261 ft-lb at that velocity.

According to the "experts", one needs at least 1000 ft-lb of kinetic energy to "ethically" kill a white-tail deer. (I'm not gonna argue about that figure.) So, this bullet theoretically (QL paper-whipped numbers) has sufficient impact velocity (according to the manufacturer), AND sufficient energy, (according to the "experts"), to "ethically" kill a white-tail deer out to 220 yards.

220 yards ain't bad, but... considering the .338 caliber and the really good bullets available in it, 220 yards is kinda "short range". It should be kept in mind though, that the manufacturer's intent was "CLOSE QUARTERS" use for this bullet. I'd say 220 yards is well beyond "close quarters".

As it turns out with this particular barrel, there is only about 0.165" of leade in this chamber. ("Leade" being the distance from the mouth of the cartridge to the point where the lands engage a bullet.) That turns out to be OK for this and a couple of other LIGHT FOR CALIBER bullets I have in mind, but not so good for "normal" bullets that weigh above 160 grains. I'm not sure how I will deal with that. I think it depends on how these LfC bullets shoot.

According to QL, 60.4 grains of Benchmark produces a MV of 3525 f/s at a max pressure of 'only' 53,835 PSI. I THINK that may be what I start out with.
Then you will know the truth, and the truth will set you free. John 8:32

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