8mm-.06 vs .308: thoughts on odd load data?

Sierra data seems more on par with what you can expect. The 308 was designed to perform near what a 30-06 would do and using IMR 4064 with a 150 gr Nosler BT the max velocity between the 2 is only 25 FPS.

The reason your seeing the close velocities is the powder itself. IMR 4064 is a faster powder an is not going to give you the better velocity in a larger case like the 8mm. If you ask me you need a better suited powder if velocity is what your looking for. Something Like IMR 4350.

The advantage is with heavier bullets, not light bullets like a 150gr bullet.

That isn't unusual. I can get near 2900 fps with 47 gr of powder in my 308 with 150"s, while I need 60 gr of powder to get 3050 fps in 30-06. That's 22% more powder for 5% more speed. And that isn't using the same powder, that is using powders that are matched to perform best in those cartridges. I can get 2800 fps with 180's in my 30-06 with 57 gr powder, while I need 75 gr of powder to get 3050 from a 300 WM. That is 24% more powder for 8% more speed.

The Sierria load is faster, but you're still burning 20% more powder to gain 8% more speed. A slower powder might help get more speed from your 8mm-06, but you're going to always see a pretty small increase in speed in relation to powder burned.

Also, anytime you're using the same bullet weight with the same powder charge in the same parent case the one with the larger diameter will have more MV. But it will also slow down faster downrange. The larger diameter bullet in the same weight will be shorter, has less contact with the barrel and less resistance so it moves out the barrel faster.

The 8mm-06, 338,06, 35 Whelen, and 30-06 share the same case. If using 180 gr bullets in each of them, with the same powder charge the 35 caliber bullet will leave the muzzle the fastest, followed by the 338, then 8mm and 30-06 will be the slowest. But within 100-150 yards those speeds will be reversed with 30-06 being the fastest and 35 Whelen the slowest. The smaller diameter bullet in the same weight will also be longer, meaning it will penetrate deeper in game.

In theory, the larger case of the 8mm-.06 should hold.more powder and thus give more push to the same.mass of boolit as the .308. Yes?

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It holds more powder, but there is a lot more to this. WHICH powder matters, and even within the same cartridge different powders work best with different bullet weights. In 30-06 the same powder I'd use with 150's and lighter isn't going to be a good choice with 180's and heavier.

Jgjgjg said:

The Sierra numbers are least arguably sensible. The Speed figures less so. I have several other manuals and the trend seems to be the newer the book the more downgraded the 8mm-06 performance is.

What are your thoughts on the above?

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In my opinion, if I were creating data and releasing data, I would not be publishing data that exceeded the pressure limits of military Mauser actions. World War 1 era M98's were chambered for a cartridge that produced 43,000 psia and by the time you get to WW2, the pressure of the cartridge is 46,000 psia. I think it is irresponsible, and if I were on a Jury that decided liability, I would rule against any Organization that published data that exceeded the pressure limits of the actions most likely to be chambered in 8mm-06. And those actions would be military actions. And the barrels would be military barrels that were deepened with a chambering reamer.

Now the 308 Win, the average operating pressures of the 308 Win exceed the proof pressures of the military actions.

Those old gunsmiths, in the era before product liability, were free to chamber old rifles to cartridge combinations that were unsafe. He had zero liability for the accident he created.The customer may have lost a hand, or face, and the gunsmith could credibly claim that it was all the fault of the customer. Neither the gunsmith, nor the customer had the slightest idea of the operating pressures of the military cartridge, the structural limits of these actions, or the pressures of the 8mm-06 cartridges reloaded by the customer. Who, if he was an Ackleyite, believed that the "principle of straightness" made the added bolt thrust go away.

Ignorance, stupidity, and superstition do not protect the ignorant, stupid and superstitious from catastrophic events. Only luck or the benevolence of God protects the unlucky from harm, and as a regular practice, I would not count on Divine intervention to save me from harm. Modern product liability law does not have exclusions for ignorance, stupidity, or unreal belief systems concerning the laws of nature. Manufacturers and creators are assumed to be knowledgeable about what they are doing, and are held to that standard.

If you want to do 150s, .308 is a better call, but for 195+ 8x57 is is a better call.

2 barrels coming off the same production line will not shoot the same velocity. All barrels are unique to them selves. If you were to use a different gun the values would be different. I've see as much as 200 fps differences between barrels with the same length.

There's nothing wrong with using the 150s in 8mm. The Speer and Hornady examples are fine deer bullets, haven't tried the Sierra. You just won't be pushing them as efficiently as the .308 will. Larger pressure vessel (including the bore)=more gas needed (powder) to propel a projectile of given weight at given speed.