Advantages of Sharp Shoulders?
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What benefits does a sharp shoulder provide? I understand the basics of how an improved cartridge compares to the original; however, I would like to learn more about how a sharp shoulder angle compares to a shallow one when capacity is the same.
I've read things like longer barrel life due to sharper shoulder keeping the convergence angle inside the neck of the brass, more accuracy (because reasons?) and longer brass life due to less working of the brass. To be frank I don't have enough experience to know what, if any of this, is true.
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Steep shoulder angles inhibit brass growth and creates a more stable condition across many firings. Shallow shoulders will allow a lot of brass flow during firing, which must be subsequently trimmed off after sizing. Trimming is much less frequent on cartridges with steeper shoulder angles.
It also causes the powder force to impact the inside of the brass neck rather than the throat of the chamber. It will typically cause a more desirable pressure curve, rather than that of shallow shoulders which will often cause a narrow and finicky accuracy node.
There is also a bit different force at play in the neck when have a sharper corner at the neck/shoulder junction. By having a more defined transition, the brass flow in the neck seems much more predictable. I'll typically see more consistent seating pressure in something with a 30° shoulder versus something with a 20° shoulder. All of my favorite cartridges have a 30° or steeper shoulder. The most stable cartridges with the widest accuracy nodes all would seem to have a good steep shoulder on them.
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@orkan Isn't this the idea behind Ackley Improved cases as well?
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So it would seem that all of what I've read is true to an extent if I'm interpreting your post correctly.
I wish I'd had understood this better before chambering a few barrels. haha
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@norcal_in_az Yes, Ackley certainly had an early understanding of this stuff.
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Thanks for sharing your knowledge dude.
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