Today, almost all firearms are made in Factories, and that has been the norm since about 1850. The problem is prior to about 1850 the vast majority of firearms (And especially the "American Rife" that name it was called in the 1700s when it was built) were custom made by gun smiths. Some were fancy, some were plan, but rarely numbered. Many were re-built well into the late 1800s (and some gun smiths were making them on equipment in use since the 1700s as late as the 1970s when the demand for black powder weapons took off).
Given that we do NOT know how many Gunsmith were making them, we do not know how many each gunsmith made, and we do not know how many were converted to other uses (i.e. shotguns once the rifling worn away) to give any number is at best an educated guess.
The biggest problem with the number 1100 is that Pennsylvania/Kentucky/American Rifles were used by Rifle regiments during the Revolution (and were used by rangers and other riflemen before and after the Revolution). 1100 sounds to low for me, that would equip just one rifle regiment and the US Army had more then one Rifle Regiment during the Revolution (Through given that Rifles had no bayonet and were slow to re-load, and when their misfired very slow to made usable, General Washington issued standard orders that any Rifle Regiment had to be supported by one infantry regiment armed with smooth-bore muskets that had bayonets, could be loaded up to six rounds a minute AND if a misfire occurred (And that averaged about one out six times the weapon was fired) could be brought back into action within 30 seconds (Rifles had to have the ball physically pulled out of the Barrel, Muskets just left the ball fall out of the smooth-bore barrel, thus smooth bore muskets were faster getting back on line).
Yes, at the time of the Revolution the Smooth Bore Musket was superior to the Rifle for general combat use. This changed with the invention of the Percussion cap in about 1820 (The idea of using what we know call the percussion Cap was first made in 1804 but the actual Cap was not invented to the original patents ran out about 1820). The Percussion cap dropped misfires from one in Six fires to one in a thousand (British test of 1830) thus permitting the replacement of the Smooth-bore musket with the Rifle by the time of the US Civil War (Thus rifles were in general use by 1861). The Minnie ball, a round with a hollow base that could be loaded into a rifle, just like a ball into a Smooth-bore musket, but then expands to engage the rifling had been around for at least 300 years before the invention of the Percussion Cap. The Minnie Ball never took off do to the high rates of misfires of pre-percussion cap weapons (The Minnie Ball would jam a rifle and be out of action for 1-5 minutes till the ball was physically pulled out) UNTIL the rates of misfires was reduced by the percussion cap. Thus the Minnie Ball was an important innovation when it was re-invented by French Colonel Minnie in the 1840s, it had been know for centuries but do to the high misfire rates never adopted. The adoption of the Minnie Ball was the result of the invention of the Percussion Cap NOT something unknown to its re-invention in the 1840s, thus it is the percussion cap that is the important invention NOT the Minnie ball.
Getting back to the Pennsylvania/Kentucky/American Rifle the number produced were higher then 1100, but no one really knows the number, no one was keeping such records (and what records that were kept are long destroyed, more do to neglect than anything intentional). 1100 is the number that can be determined. Remember these rifles were NOT made for the rich as collectibles, but for working class Americas who used them to hunt game not only for food but for the pelts. Once these rifles were worn out, most owners did not keep them (some did update them for example a Rifle Won by Davy Crockett in the 1820s was later converted by the request of one of his child to a Percussion from the Flintlock it was originally made in). The metal in them had value and thus sold but many were buried with their owners such as the famous Story Of Lewis Wetzel and his rifle "Long Tom" (For more on Lewis Wetzel see
http://www.earlyamerica.com/review/spring97/wetzel.html a rifle was found buried with a man in the area where Lewis Wetzel as suppose to be buried and the same report said he was buried with his rifle for his relatives did NOT want that weapon in their home for it had killed to many people).
One of my favorite observation when I go to a Colonial era house is the constant reference to spinning wheels. Many spinning wheels survive for no one wanted just to burn them (When no longer is widespread use after about 1830 the only real use for them) while the male equivalent, the set of nails used to convert flax into thread for women to spin into thread disappeared. The nails could be used otherwise, especially after 1850 when homes converted from tongue and grove construction (Common pre-1850) to what we call nail construction (i.e. using nails to hold the wood together instead of cutting the wood with tongues and groves and then fitting them together). Thus the nails had a subsequent use and were used and most such tools were thus destroyed. Spinning wheels had very little parts and could be used for anything but spinning so spinning wheels survive in vast numbers compare to the nail board men use to slap the Flax into and then pull the flax threw, and men did this constantly till the flax was thin enough to be spun by women in spinning wheels (and then when spun taken to a weaver who weaved the threads into cloth for clothing).
I bring up the Spinning wheels and Nail boards for about the same number of each was made (someone needed to make the threads and someone needed to take those short threads can spin them into what we would call threads). Like the nails in the boards, the metal of an old and worn out rifle had a market price and thus could be sold. Many were so sold (Civil War Cannons were collected and melted down during WWII in metal drives to help solve the steel storage caused by the demand for Steel during WWII for another example of value metal had). Now the Steel used in such rifles are low value Steel today (Nickel was not discovered till 1854, and nickel mixed with steel makes the steel stronger then steel without nickel, the better steel of the post Civil War Era saw a lot of older rifles just disappear as people threw them away, or just sold them for the value of the Steel in the rifle so they would have some additional money to buy a more modern weapon in the late 1800s).
Just comments on the fact 1100 seems to low a number, but also why only a couple of hundred survive to this day. The US Population was only 5 million by 1800 (
http://en.wikipedia.org/wiki/Demographic_history_of_the_United_States) so we are NOT talking about more then 50,000 Rifles (One rifle for every 100 Americans,please note I believe 50,000 is five times to many, less then 1% of the population has such rifles so I suspect about 10,000 rifles which would mean one out of every 500 Americans) but a number like 1100 would be one out of 5000 Americans and that is to low for how while known the Rifle was known in the 1700s (While enough to already have its own name by the 1700s, the "American Rifle".
According to this source, Pennsylvania supplied Rifle Regiments had 12 companies of 68 Privates each (Total of 816 Rifle men NOT including officers and NCOs). Virginia Regiments had 3 companies of Riflemen and 7 companies of Musket-men per regiment (64 Privates per company or 192 Rifle Men per Regiment, the rest being Musket-men).
http://www.history.army.mil/books/revwar/contarmy/CA-04.htm#table3Later on the Author points out Virginia raised 8 Regiments, thus 576 Rifles were needed (Again this is the number of privates, NCOs and Officers are NOT counted, through the NCOs probably carried Rifles while the Officers did not).
http://www.history.army.mil/books/revwar/contarmy/CA-07.htm#table5Maryland and Virginia also operated a Combined Rifle Regiment along Virginia lines of 420 Officers and men. This was captured and cease to be an effective unit after 1776. for more see:
http://en.wikipedia.org/wiki/Maryland_and_Virginia_Rifle_Regiment#DisbandingIn any regards, this regiment used about 400 rifles.
Thus with just these three units you had a need for 1792 Rifles. These are just the "Regular forces"
the Militia also had rifles (through as a lower percentage then the Regular Army with the New England units have almost no Riflemen). The US Government did NOT Supply the riflemen Rifles till 1804. Till 1804 Riflemen received extra paid to compensate them for the use of their own rifles. Just further evidence that the 1100 number is just to low.
To give the above numbers some prospective, remember when Britain and France declared war on Germany in 1939 both mobilized their Armies. Britain had in service (Including its regular forces and the mobilized reserves) one out of every 48 Britain males. France, which had the Draft and almost universal military service, called up one out of 8 Frenchmen, Thus one out of 100 American being a Riflemen would still make him a rare breed in terms of people serving in an Army. One out of 1000 would make him almost unknown unless he was operating some big piece of equipment like a Fighter plane (Rifles were important during the Revolution but no where need the power of a modern fighter-bomber). Just some numbers to put the above numbers in prospective.