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March 11, 2010, 08:48 PM | #1 |
Senior Member
Join Date: January 7, 2010
Posts: 155
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Old Lyman manual and OAL'S
I ordered a 74 model Lyman Pistol and cartridge manual. I thought the OAL was always the same on a given caliber round but this manual shows a different OAL. for most every load in a given caliber. Which way is right...all have the same oal or each different load has a diff. oal? Thanks, FullCry
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March 11, 2010, 10:15 PM | #2 |
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Join Date: December 24, 2008
Location: Loveland, CO
Posts: 1,476
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You could expect "seating depth" to be the same for a given caliber. The variation comes from the length of the bullet. However, reloading manuals haven't listed seating depth since the early 70's, and only a few did.
What is important is the height of the base of the bullet above the inside bottom of the case. That is what dictates pressure. |
March 12, 2010, 07:52 AM | #3 |
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Join Date: November 8, 2007
Posts: 2,001
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Cartridge overall lengths (COLs, but sometimes written COALs or OALs) are not always the same for a particular cartridge. There are some limits on how long or short a cartridge can be loaded, due to dimensions of the gun that is to use it (e.g., magazine length, amount of freebore in the barrel) and the bullet (e.g., nose shape, length of straight section). In auto-loading pistols, the COL often needs to be adjusted to get reliable feeding.
Because the peak pressure when a short pistol cartridge is fired depends strongly on its COL, the manuals typically list the COLs that were used to produce their pressure-tested load data. That way, you can use the same COL for your loads and avoid a pressure-changing difference (although there are other pressure-changing factors). If you find that you need to change the COL, you will know by how much and can make appropriate calculations to adjust the powder charge to keep peak pressure about the same. SL1 |
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