An informative and engaging post there, Scott.
Particularly valuable was the detail on the Mk VI and VII cartridge, and the popular confusion between the Martini-Henry and the Martini-Enfield.
And that on the Vetterli—though I wonder if there might be some confusion over this rifle? Philip Orr (in The Road to the Somme) points out that Vetterlis came in on the Clyde Valley and ended up in Cavan-Monaghan; they were unpopular because they were stamped annunciata, which was believed to mean they had been blessed by the pope! Is it possible that these rifles might have been seized by the IVF subsequently, after the UVF had been locally depleted through enlistment in the 36th Division? Or maybe even sold or swapped between the volunteer forces? The same Hamburg arms dealer supplied both UVF and IVF so could have included Vetterlis in both shipments, but it’s interesting that the guns all ended up in the same part of the country. Bannerman might be able to cast a light on this?
The Danish Krag-Jorgenson comes as a surprise—though this was a good rifle, the first “small calibre” long-arm adapted by the US military, easily recognised by its horizontal-clip magazine. Rather quickly supplanted by the all-American Springfield Model 1906 (“ought-six”), it remained in use for many years, as cheap military surplus, so doubtless was shipped to dealers far beyond America's shores. Gregory Peck used one on the screen to shoot a mad dog in To Kill a Mockingbird, a plausible detail (the film is set in the Hungry Thirties, when cheap military-surplus guns were all that most could afford).
That the Howth Mauser was believed to be an elephant gun probably had to do with its large bore and black powder charge, which gave it a very loud report, and with the dumdum bullets many of them fired and which could do appalling damage (like taking a head clean off, as happened outside Jacobs).
The belief also reflects on the youth and naiveté of many conscripts, which, in combination with bad leadership, accounts for the carnage at Mount Street Bridge—though the impressive effectiveness of the rebels here, well described in the essay, was a factor too, of course. Margaret Skinnider claims to have overheard a British officer frankly acknowledging the superiority of rebel shooting over that of his own men.
As for the cast-lead shotgun slugs: might other slugs have been manufactured in the field by cutting half-way through the cartridge-casing forward of the brass base? Or opening the front of the cartridge and melting candlewax onto the pellets? These are old tricks; any evidence they were employed?