Thanks for the kind words.
There's a difference between producing enough long arms in the US, however, and simply having enough to equip the existing forces as of December, 1861, and any additional forces raised.
The only truly exhaustive and comprehensive lists for the Army would be in the Ordnance Department's records, which are available on microfilm at NARA; they are not on-line, which leads to various individuals using various other sources, including Congressional reports, communications between the Ordnance Department's investigators and various contract manufacturers, etc. That, in itself, is fairly spotty; add in the reality that the Navy and Treasury departments also had wartime procurement responsibilities, much less that in a federal system, every state and even territorial government had an executive branch and military department with the authority to raise and equip troops, entirely separately from the federal government and its departments, and a comprehensive survey of the issue becomes even more problematic. Then add the reality that the civilian arms stockpile and trade in the US was, as always, significant, and the potential sources of supply becomes even more diffuse.
One can come up with various lists, most of which are reasonably sourced in terms of the US Government arsenal production of (for example) the M1855 and M1861 rifle musket; but after that, there is the wartime production by civilian contractors of the M1861, the "Special" Colt 1861 design (which had features both of the M1861 and the British P53 that had been made under license by Robbins & Lawrence for the British Army during the Crimean War because of shortcomings in the British supply chain), the Remington contract design (which had a lot in common with the M1841 rifle, which was a modern percussion weapon that remained in production until well into the 1850s);, and then the changeover to the M1863.... these lines were being set up in 1861-62, began producing in 1862-63, and hit their stride in 1863, but the issues of supply chain for components gets pretty convoluted before deliveries began...
The prewar production numbers for the USG are pretty well known, but how many of those remained in loyal hands in the US vs. those that the rebels took control of in 1861 are another delta; there are estimates that I've read that less than 12,000 M1855 rifle muskets and 15,000 M1841 rifles produced on federal account actually ended up in what became rebel states in 1861 - if so, then the entire remaining stock of these modern weapons - at least 12o,ooo, if not more (150,000 or more is possible) - were in loyal states. Then, in terms of US-made rifles and rifle muskets in the standard calibers (.54 and .58) in US hands by the winter of 1862, when any conflict along these lines might break out, are the M1861s produced at Springfield (~40,000 or more by January, 1862), the R&L made P53s that were not exported to the UK (possibly as many as 10,000 to 15,000, in .577 or .58), the 4,000 or so M1859 Sharps breechloading rifles manufactured before the wartime orders for Berdan et al, etc. There are 200,000 or more weapons, at least, in these categories.
Then consider the reality the US had begun to mobilize in April, 1861, a full 9-10 months before any Anglo-American conflict would or could break out in the winter of 1862, and consider the flood of British and Belgian made Enfields/P53s (in .577 or .58); Austrian-made M1854s and variants (in .54 or .58), the M1851 "Saxon" rifle in .58, etc. These were all modern rifle muskets, designed for percussion caps and in calibers that were standardized; given that 330,000 P53s and 220,000 M1854s and 25,000 M1851s were imported in 1861-63, the numbers that came into the US and were accepted by Army Ordnance alone in 1861-62 numbered well between 200,000 and 300,000 of those weapons, as well.
Then consider older military rifles, whether US Government procurement (~25,000 M1819 breechloaders and ~60,000 M1803 to M1817 muzzle loaders, all in standard .52 or .54 calibers) or older European weapons (usually in the larger "Minie" calibers in the .69 to .71 range, so heavy, but still useful) all of which had been manufactured as or could be converted to percussion cap, or US civilian manufactured rifles. Then consider the vast stocks of US Government procured muskets, both made as percussion (275,000 M1842) or converted (675,000 M1816/M1822) which in a regiment with mixed weapons, add to the volume of fire and are as deadly in broken country as any rifle, and which, in fact, could be converted to rifled muskets. Then consider carbines (USG production or contract), civilian muskets, and shotguns, all of which could accomplish the goal of sending lead down range in vast quantities.
By the first quarter of 1862, that's a SWAG/ROM of a half million modern percussion rifles and rifle muskets, of US and European manufacture; presumably 100,000 or so older or 2nd-line rifles; and the same or more (~500,000) in US-made percussion muskets, designed as such or converted; etc. That's more than enough to equip an army of a million infantry; certainly more than enough to equip the 527,800 regulars and USVs on active duty in December, 1861 plus as many more of the 506,000 as mobilized historically to the call late in 1862 for additional USVs, plus as many state troops, militia, or auxiliary federal troops as one could wish for...
All of the above is basically just back of the envelope, of course; the only really reliable numbers are in NARA, and until their collections are digitized, they will remain there.
Best,
Bringing the