P O Ackley
How come either P.O. or someone else has "Improved" just about every cal. based on the .308, and 06, except the .270 Win. It is not even mentioned in his handbook vol.2. I'm sure there are other cartridges that will duplicate it's performance, but that never stopped a wildcatter before. Has any one here Improved the 270 on his own? I've had, or have just about every one of his cartridges from the .223, to .375, but not the 270. HAWKSHAW
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Vol I, pg 382. .270 Winchester Improved(Ackley). He states that it is inefficient and that the standard form should be better. 0 -
I'll check that out. So what about the 25-06 imp.? Is it even more inefficient? THX HAWKSHAW 0 -
Hawkshaw,
The terms 'efficiency' and 'inefficiency' have more than one connotation or definition especially when it comes to cartridges and reloading. Many folks have too narrow of a perspective of what efficiency really means when reloading and shooting.
P.O. Ackley's observations about the inefficiency of the .270 Win. stem from the lack of powder selection available for that cartridge and the bullets used in combination with those powders. Currently that same determination is made because the manufacturers decide to use short barrels to save money in manufacturing while kowtowing to shooters who believe that short barrels are necessary.
The basic '06 case itself is a design relic of the military's need for no-fail feed and function for battlefield conditions. Understandable to be sure. In essence, the shape is exaggerated with long tapers to aid in never fail feeding. But these same tapers do not contribute to the efficiency when it comes to consuming the powder which can be used to fill the case. Fact is, they are detrimental to that same efficiency.
By 'improving' the case we aren't just simply increasing the case capacity in order to increase the horsepower. This is often the lackadaisical criticism levered against the improved cartridges by those exercising the mindless repetition of incorrect information. In reality, we gain efficiency by being able to use a broader selection of powders which can provide a better match to the bullet design or weight. With careful testing of loads we can establish a combination which will consume all of the powder in the case and first few inches of barrel while producing the maximum amount of plasma to push the bullet out of the barrel at the higher velocity but within the limits of standard pressure. Think of it like better gas mileage in a car. We are trying to make the best use of the amount of powder available in the case. This is the situation with the .25-06 AI, it take some investigation and testing to achieve efficiency. A barrel longer than 22" helps, too...
The .30-06 Springfield and .308 Win. don't tend to benefit from improving the case shape as much as other case designs. However, when we neck either or both of those cases down, we do see greater efficiency through the improved shape. A great deal of work has been done privately on the variations of improvements made to these cases. The improved body taper has loosely been standardized but it's the angle of the neck which receives the most attention. Ackley used the 40 degree shoulder as his standard, yet we're finding that the area somewhere between 30 and 35 degrees provides more subtle refinements in efficiency and balance.
Best.0
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