Thread: OAL = COL ?
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Old September 2, 2012, 10:34 AM   #18
snuffy
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Join Date: May 20, 2001
Location: Oshkosh wi.
Posts: 2,779
Quote:
Book oal is meaningless to a handloader.

I don't know why they even include it in the book.

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No it's NOT! It's the overall length of the bullet-case used in their testing---period! If you use a different overall length, then you're not going to duplicate their shown velocity. But more important, you're not going to duplicate their pressure either. In fact, if you go with a shorter bullet seating depth, you'll RAISE the pressure. Sometimes to a dangerous level.

Bullets of the same weight are made with different profiles. That means some are more pointed, or have a truncated cone profile. This makes for different full caliber bullet diameter that actually rides the bore. Some are a cupped bottom, or hollow base profile that pushes the weight forward and results in a longer section that rides the bore. This results in more friction with the bore. Friction and weight are responsible for pressure. That's all figured into the charge weights for the powder.

As some said, I take most manuals as suggestions. As long as the weight is the same, or within 5 grains, I use the suggested starting powder charges as just that, a place to start.

Fly sub was correct to be worried his suggested shorter seating depth might produce higher pressures. But Hornady took the shorter depth into account when testing and publishing the load data.

9mm is a high intensity, high pressure cartridge, it's loading parameters are very narrow. But most guns chambered for it can withstand higher pressure without letting go. Reading pressure from what the fired case looks like is like reading tea leaves. If you've shot your pistol a lot, excessive recoil/muzzle flip will tell you somethings not right. Excessively flat primers or extractor damage to the rims helps identify excess pressure.

Quote:
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WTH is that? French latin? What does that say, and how does it pertain to reloading?
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