I have a photocopy of the original series, plus an NRA reprint on Civil War Small arms which as I recall has a slightly different version fo the Weller articles. The passage I quoted re Henry/Turner was from the 'reprints'. I don't recall seeing any reference to the provenance in that. At work right now, so don't have any info with me to check.
The Turner pic is on my Long Range Muzzle Loader web site at www.lrml.org . There's some background info and original texts by Whitworth linked from the 'Directory' section.