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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
.280 AI vs .284 Winchester AI...
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<blockquote data-quote="Trickymissfit" data-source="post: 450249" data-attributes="member: 25383"><p>except for the shoulder angle, the case fits all of Ackley's specs. He would have probably not called it an improved case because he would have increased the neck length to about .31" by pushing the shoulder back a little bit. For the case to be an improved case you have to be able to chamber and fire a factory case in the chamber. All I'm saying is that by changing the shoulder angle to 40 degrees you will not see much improvment in velocity, but have a slightly better flame path (very slight). But you push the shoulder back .06 to .093" with the 40 degree shoulder, and you have a different ball game. (also helps with case shrinkage issues during fire forming) You will see little if any loss in velocity, but increase case & barrel life signifcantly (6.5/.284's often eat barrels in 600 shots). Ackley didn't always improve a case to gain velocity, and often did it to increase case or barrel life. He was just way ahead of his time. </p><p> </p><p>this weekend I'll make a CAD drawing of the two cases. One with the 40 degree shoulder and the other with the standard 35 degree shoulder. Yet keep the shoulder deminsion in the same place to see how the neck comes out. May do a third one with a .062" shoulder setback as well. Guys I know that are shooting 6/.284's (a real barrel eater) are pushing the shoulder back .100", and seeing no loss in velocity while the barrels lasts much longer. There are a couple I know that have gone so far as to push it back .150" (also shortening the neck a little bit), and are seeing about a 75 fps loss in velocity with much tighter groups. These barrels tell me that Ackley's vision of overbore was dead right.</p><p>gary</p></blockquote><p></p>
[QUOTE="Trickymissfit, post: 450249, member: 25383"] except for the shoulder angle, the case fits all of Ackley's specs. He would have probably not called it an improved case because he would have increased the neck length to about .31" by pushing the shoulder back a little bit. For the case to be an improved case you have to be able to chamber and fire a factory case in the chamber. All I'm saying is that by changing the shoulder angle to 40 degrees you will not see much improvment in velocity, but have a slightly better flame path (very slight). But you push the shoulder back .06 to .093" with the 40 degree shoulder, and you have a different ball game. (also helps with case shrinkage issues during fire forming) You will see little if any loss in velocity, but increase case & barrel life signifcantly (6.5/.284's often eat barrels in 600 shots). Ackley didn't always improve a case to gain velocity, and often did it to increase case or barrel life. He was just way ahead of his time. this weekend I'll make a CAD drawing of the two cases. One with the 40 degree shoulder and the other with the standard 35 degree shoulder. Yet keep the shoulder deminsion in the same place to see how the neck comes out. May do a third one with a .062" shoulder setback as well. Guys I know that are shooting 6/.284's (a real barrel eater) are pushing the shoulder back .100", and seeing no loss in velocity while the barrels lasts much longer. There are a couple I know that have gone so far as to push it back .150" (also shortening the neck a little bit), and are seeing about a 75 fps loss in velocity with much tighter groups. These barrels tell me that Ackley's vision of overbore was dead right. gary [/QUOTE]
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.280 AI vs .284 Winchester AI...
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