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Old September 10, 2001, 06:30 PM   #1
Jim March
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Join Date: February 14, 1999
Location: Pittsburg, CA, USA
Posts: 7,413
Is there a difference in optimal barrel bore between .45ACP and .45LC?

c title. I'm also aware there may be twist rate issues.

This stems from a possible concern that a Ruger SA in "double-caliber" may not ever achieve optimal accuracy in .45ACP, because I seem to recall that there may be a small difference in peak barrel bore.

I know that Ruger is using a 16:1 twist rate on all SA .45cal guns, which seems like it would do OK for most of the loads I'm contemplating. Does anyone know what a peak .45ACP slidegun twist rate is, as done by Wilson/Kimber/etc?
Jim March
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Old September 10, 2001, 11:39 PM   #2
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Join Date: October 29, 1999
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Lyman uses twist rate in their test guns of 1 in 16" for both the 45ACP and the 45 Colt.

Pre WWII .45 Colt bores were in the neighborhood of .454 while post war guns were/are mostly made with bore diameter of approximately .451.

.45ACP nominal bore size is .451.

Hence a barrel for .45ACP should be just fine for .45 Colt. Some .45 Colt dies may not size the case down far enough to grip .451-.452 bullets firmly enough. In that case trim the expander plug to not over .450.

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