"P.S.: Honey, if you read this, blame it on Big Stick, Eremicus, and Ken Howell." Don't blame it on me, Rick! I'd never recommend an Ackley "Improved' to anybody.
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<br>Now I have to defang the inevitable allegation that I have no experience with an Ackley cartridge (I do -- with a nice custom 1903 Springfield sporter) or that my rifle wasn't chambered to the correct specs (Ackley did it). But that's an old story, already told on another board, where it brought down wagon loads of fresh manure onto me. So there's nothing to gain by repeating it here. Extremely unpleasant, personally abusive posts would inevitably follow.
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<br>We now have better powders for both of these versions of the '06 than those I could get in 1955. Even so, the improvement of the Ackley rechambering is slight. Compare the results below, in a modern .30-06 rechambered to the Ackley version. Both sets of data come from the same bullet (180-grain Nosler) and the same seating, in a 24-inch barrel, at the same maximum peak pressure. The slight increases in velocity are understandable, since fire-forming the cases to the Ackley chamber increased the water capacity of the .30-06 from 68.2 to 69.3 grains -- not a great capacity increase (that's an increase of only about 0.95 grain of powder).
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<br>H-414 -- 2,870 ft/sec to 2,880 ft/sec
<br>W-760 -- 2,850 ft/sec to 2,860 ft/sec
<br>H-380 -- 2,780 ft/sec to 2,800 ft/sec
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<br>Notice that the greatest velocity increase occurred with the least productive of these three powders and didn't match the velocities produced by the other two powders. Other powders failed to produce comparable velocities at the same peak pressures, so presumably these are three of the best powders for either the original or the Ackley version of the .30-06.
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<br>I found the 40� shoulder troublesome. The necks of the cases frequently 'turtle-necked" (collapsed into the shoulder during the seating of the bullet).
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<br>None of this negates the basic advantages of other truly improved cartridges. Extending the body of the case forward produces a good bit more real improvement than merely blowing-out the body and increasing the shoulder angle. There's VERY little difference, for example, between the capacity increases of the 30� and the 40� shoulder angles. Also, the smaller the difference between the shoulder and neck diameters, the less a meaningful increase in capacity is even possible.
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