About:

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8/8/62 Hindman to Rains, Cooper, Carroll via Fort Smith [...] Col Cooper will take either West’s or Howell’s Company, as he prefers, with 3 of the 6 bronze guns moved from Ft McCulloch [left there by Pike] Col Carroll will take the company not selected by Cooper and the remaining 4 bronze guns"
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and

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Is it possible that in the second message a sentence is lacking?
Something like:
"...3 of the 6 bronze guns moved from Ft McCulloch, and 1 of the 2 left there..."
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I have finally located the original:
http://mdh.contentdm.oclc.org/cdm/compoundobject/collection/mack/id/11175/rec/1 (Alexander Papers Collection, page #1, item #1)
page 272, or image 271 of 325
The "text" label reads (with my corrections):

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[...] Col. Cooper will take wither [either] Wheat [West's] or Howells [Howell's] Company, as he prefers, with three (3) of the six (6) bronze guns moves [moved] from Fort McCulloch, and one (1) of the two (2) bronze guns orders [ordered] to be moves [moved] from that post. Col. Carroll will take the remaining one of the two companies last named, and the remaining four (4) bronze guns. [...]
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Quod erat demonstrandum.