Those who may have to identify historic gun parts at some point in their 
lives (or simply love oogling lovely old guns) might want to snag-onto 
copies of these two references ... they are FABULOUS & FREE !!!!

Regards,

Bob


U.S. Ordnance Department Memorandum No. 15 (1873), wherein the U.S. War 
Department is considering EVERY American-made carbine and musket 
(including wooden models) then available (including foreign models) for 
use by the U.S. military forces ... and has a section for each gun 
submitted for testing/evaluation, but also in the report is included 
a/photographic plate/ of each disassembled gun, and /all its parts 
nicely laid-out/, with a key ...

http://books.google.com/books?id=4R25AAAAIAAJ


Norton's beautifully illustrated 1880 compilation of the latest & 
greatest inventions and improvements in American small & sporting & 
military arms & ordnance (replete with cutaway drawings of working parts):

https://archive.org/download/cu31924030759702/cu31924030759702.pdf

Or you can view the book directly online with their excellent book 
viewer, for example ...

the Remington magazine gun (Keene's patent) section ...

https://archive.org/stream/cu31924030759702#page/n161/mode/2up

Sharp's rifle Model 1878 ...

https://archive.org/stream/cu31924030759702#page/n179/mode/2up

Be sure not to overlook Norton's chapter on the Gatling gun ... 
copiously illustrated ... (he even depicts one mounted camel-back ... 
the ultimate "Apache gunship" of its day for the Camel Corps ?):

https://archive.org/stream/cu31924030759702#page/n257/mode/2up

  Here is a version of this book digitized and made available for 
download by Google Books (although a few of the scanned images are 
inferior to those in the one scanned by the Internet Archives, 
by-and-large the Google Books images are usually consistently higher 
resolution than those on the Internet Archive ... although this may not 
be the case in this particular example ... 3especially when using their 
fine online book viewer app) ...(lately it seems Google has tended 
making these FREE old illustrated books really difficult to find in 
their search engine after various booksellers [paid advertisers of 
theirs ?] have taken to selling knock-off print-on-demand copies of 
these at highway-robber prices ... just search for it ... you'll find a 
HUNDRED ads to buy a modern knock-off before you'll find the freebie):

http://books.google.com/books?id=zl9GAAAAYAAJ

Norton's 1872 edition on Google Books is here:

http://books.google.com/books?id=vl5GAAAAYAAJ