Another interesting angle, with regards to rifle transactions in the procurement period for Lewis at Philadelphia 1803. Bear in mind this is all complicated, and not totally fleshed out in my mind - this could be a good dialogue if anyone out there has their own info to share to help me out or correct me - but here goes:
Who's who in March - June, 1803 at Philadelphia, Lancaster and York:
Israel Whelan - purveyor of public supplies. Basically he was the army's purchasing agent, who was responsible for obtaining materials for Meriwether Lewis per the direction of Henry Dearborn's in Dearborn's March 14, 1803 letter.
Tench Coxe - replaced Whelan as purveyor later in 1803
William Irvine - superintendent of military stores at Schuylkill arsenal
Gratz brothers - Philadelphia merchants Hyman and Simon Gratz
Joseph Simon - trade agent / merchant in Lancaster PA
Solomon Myers - trade agent / merchant in York, PA
Summary of rifle trade and US rifle procurement 1792 - 1803 in Philadelphia / Lancaster / York - Gratz Bros, Joseph Simon and Solomon Myers:
This was a close-knit and interrelated group of jewish merchants / traders that worked between York = Lancaster = Philadelphia. Their trade worked westward, with the Indians, but also eastward. These agents / merchants worked with, and coordinated at least some of the efforts of the Lancaster and York rifle makers to provide contract rifles for the US government at Philadelphia (Schuylkill Arsenal). Joseph Simon actually for a long time was partner with William Henry of Lancaster, going way back to the 1750's or earlier, and actively obtained / delivered 1792 contract rifles (Moller), who in turn delivered them to Philadelphia. The Gratz Bros. were also key merchant for US arms from Lancaster / York. For example, when US muskets were manufactured by Jacob Dickert in 1798, his deliveries were coordinated with the government by Simon and Hyman Gratz (Papers of the War Dept). Solomon Myers was brigade inspector for York county, and he held the main role of delivering the 1792 / 1794 contract rifles from York to the US government, and delivered indian rifles made in York to the government in Philadelphia in 1803.
Indian trade rifles: Up to late 1803, while a good number of 1792 / 1794 contract rifles were still in storage at Schuylkill arsenal, indians usually received 1792 / 1794 contract rifles (Moller). It was not until roughly September, 1803 after Tench Coxe replaced Whelan, that the US appeared to begin contracting for new rifles made for indian trade in appreciable numbers (few known before that per Moller). for example in the fall of 1803 Coxe was in direct communication with Lancaster and Solomon Myers at York for indian rifle procurement.
Meriwether Lewis procurement period (March-June, 1803) in Philadelphia:
March 14, 1803 - Henry Dearborn, sec. of war, has his chief clerk write to Israel Whelan to obtain any materials that Lewis may require. He does not mention rifles, or anything specifically. On March 24, Dearborn follows up with a letter to Whelan an indicating that he will send a check for $1,000 to obtain equipment for Lewis. apparently Whelan would have no idea that Lewis was obtaining any guns at HF - perhaps assuming that rifles would be part of what he will supply to Lewis.
May 6, 1803, the Gratz brothers at Philadelphia receive payment for 20 new rifles at $13 each (Moller). These are paid for directly by Whelan, and delivered to William Irvine. Based on what we know from above, these could well be Lancaster or York made rifles. In George Moller's book, he assumes these rifles are intended for Indians, and possibly imported, since he never heard of the Gratz Bros. We do know that there were rifles traded to the Indians through this same period, but as Moller notes they had used rifles in public storage at the arsenal. A letter written by Dearborn in this same period talks about Whelan obtaining rifles for the Indians from Irvine (therefore from public stores). So why would Whelan go through the Gratz bros. unless the government wanted brand new rifles for a more important reason (if they still had plenty of 1792's)?
May 7, 1803, Lewis arrives at Philadelphia from Lancaster - he then works with Whelan to obtain everything he needs. According to the receipts, some of Lewis' purchases were paid for out of the indian dept. Lewis purchases his gun slings (perhaps for the 'new" rifles he sees at Schuylkill arsenal), and other riflemen equipment in Philadelphia. His purchases shown on receipts include 10 packing boxes for rifles. Does each box possibly hold two rifles? At the same time, he obtains boxes for swords - though he never mentions buying swords in Philadelphia, he must have since they were included on the expedition. Therefore this could explain why additional rifles were not listed either.
This could all be coincidence, but who knows? Why else would Lewis take 10 rifle boxes from Philadelphia? Did they not have boxes for rifles at HF? I don't know why not since they shipped from there for the government. I am convinced he obtained guns at HF, but as Mike notes above also, it is likely that other rifles were obtained also. After all when he left HF the first time, he went through York and Lancaster and would have seen what the makers have to offer.