Home Forums Hunting & Shooting Hunting Rifles Why is .338-06 with 200 grain bullets faster than .30-06?

Oops, I only read the second page, didn't see all the earlier posts that explained this much better than I did.

What about the fact that you can use a faster burning powder in a larger bore and keep things at the same pressure with the same weight bullet. What is the physics explanation for this?

Bb

Same reason a .308 will push a 130gr bullet a lot faster than a .260 will?

space time continuum, it's tied in there with the theory of relativity

In addition to larger bullet area for the gas to push against, I had it in my head that because the bore is larger, there is more volume in the bore to act as a gas expansion chamber.

To that end I think that a larger bore size to some extent acts similarly to adding a couple of inches of length to a barrel. Both have the effect of increasing bore capacity and velocity potential.

I am prepared to be shot down in flames if that's wrong.

All I know is it allows me to push a 160gn bullet to over 3000 FPS with a .308 case necked up to .338. Can't do that with a straight .308 or a .308 case necked to 7mm, .260, 243, etc.

bobnob,

That's also correct.

There's actually more than once factor that goes into the velocity advantage a larger bore has over a smaller one, given the same case. The general rule is that potential velocity will increase at 1/4 the rate of any increase in bore area. The .338 has a bore area of about .0897 inch, versus .0745 in a .30-caliber bore. Do the math and we find the .338 has just about a 5% advantage over the .30 caliber, given the same bullet weights.

Case capacity for this formula (or any other purpose) is best measured using water, with a bullet seated in a fired case, instead of just filling a case with water to the base of the neck.

Muzzle velocity is one factor. But with the lower sectional density of a 200 grain .338 bullet compared to a 200 grain .308, I would expect the terminal effect on Game past one hundred yards would be different.

Am I wrong? Someone tell me if I am.

Sounds like you are right but no expert am I.

The wounding effect might well be different for a couple of reasons: the SD difference could cause more or less penetration; while the extra calibre size will cause a bigger hole on entry at least.

Add to that, that all other things being equal, the .308 cal version of the 200 grainer will have a superior ballistic profile and carry speed better the further away the target.

So I'd have thought anyway.

- Bob

Spliting some mighty fine hairs. The 200 gr bullet from the 30-06 will still out penetrate 200 gr bullets from the 338-06 at all ranges.

The 100-150 fps or so advantage at the muzzle gives the 338-06 an energy advantage at close range, but it is offset by less penetration. Either will take any animal in North America at close range. But at ranges beyond the 200 yard mark the 30-06/200 will be faster, penerate deeper, and have more energy. The difference is small, but it is there. Since the 338 starts faster, it is still slightly flatter shooting, at least to 500 yards which is as far as I ever ran the numbers. But the difference is less than 1" at all ranges.

I owned a 338-06 for several years. Liked it well enough. But it offers no real performance advantage over a 30-06 loaded properly.

The .03" diameter advantage is a non-factor. Shoot both into game, measure the diameter of recovered bullets after expansion and I'd bet you could never tell the difference.

You'd probably have a hard time telling the difference on most game animals either. You buy a 338-06 to have a good round that is just a little different from what everyone else is using. You buy the 30-06 to keep your life simple. Neither is a bad choice. I sold my 338-06, not because I didn't like it, just to simplify my life.

Egad! This thread is 11 years old!

A good one though.