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Old December 27, 2009, 11:38 PM   #1
Plaz
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Cartridge length tolerance and consequences

I am reloading 45 ACP. The book says the length of my reloaded cartridge should be 1.23 inches. Sometimes I exceed that length.

Question #1: How much tolerance do I have in length?

Question #2: Would 1.244 be unacceptable for my reload of 45 ACP when the book specifies a length of 1.23 inches?

Question #3: What are the consequences for exceeding any length tolerance?
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Old December 28, 2009, 06:13 AM   #2
sourdough44
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That 1.244 with a book 1.23 would not be a problem in my loading. There is less room to vary with handguns, compared to rifle. I also load at mid charge levels, so at max it would mean more. Semi-auto handguns require careful length to cycle reliably, within a short range. Of course the powder speed & charge weight have to be matched to the cartridge. There are a multitude of bullets styles, book COLs can vary some with very similar bullets. This is where I cross reference several manuals & choose a COL to go with. If it's rifle I measure the length at which the bullet will touch the rifling, then back off a tad.
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Old December 28, 2009, 07:24 AM   #3
darkgael
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COL

Excessively long cartridges are going to present problems both fitting into the magazine and feeding from it, depending on the bullet. I loaded up two different 200 grain bullets the other day after a similar question was posted. The two seated at different lengths from the same die setting. The longer ones would not chamber fully - the gun would not go into battery. One was a 200 grain LSWC from an H&G mold, sized to .452"- at an OAL of 1.207", they would not fully chamber. Reseated to 1.17", they worked perfectly well. The other 200 grainer was a FMJ - at 1.215", it chambered just fine. .
Depending on the bullet that you use, you will find quite a bit of variance on OAL. Just looking in the Lee "Modern Reloading" manual shows minimum OALs from 1.150" to 1.275".
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Last edited by darkgael; December 28, 2009 at 07:55 AM.
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Old December 28, 2009, 10:25 AM   #4
wncchester
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"Question #1: How much tolerance do I have in length?"

Usually quite a bit of tolerance, especially if you're only referning to a book OAL.


"Question #2: Would 1.244 be unacceptable for my reload of 45 ACP when the book specifies a length of 1.23 inches?"

Yes. All the book OAL means is is it's the length they used to develop the load. Vast differences can make some difference in peak chamber pressure with max loads. But any common sense seating difference won't matter, not enogh to blow anything up anyway. Your very small difference example. either direction, is quite safe.


"Question #3: What are the consequences for exceeding any length tolerance?"

It really isn't a "tolerance." Much longer rounds (or much shorter) may not feed but the limits vary with the pistol. Seating longer in a handgun reduces chamber pressure. Most of the time.
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