I think you need to do more research on your "great great grand dad that was in the revolution", as weapons changed over time during the war. The American Revolution can be broken down into Early - Pre-1777 - Mid- 1777 til 1778 Late - 1779 til1781
- Early war or what is sometimes called the New England & New York Campaigns
- Common civilian smoothbores & fowlers, Committee of Safety muskets, Brown Bess, and older French musket from the F&I war such as the model 1728
- Rifles are a Pennsylvania / Maryland / Virginia / Carolinas thing
- Mid War - The Battles in New Jersey, Capture of Philadelphia, Valley Forge and Monmouth
- After the battle of Saratoga in 1777, large number of French 1763 or 1766 Charleville muskets start making their way to the Continental Army
- Captured German Muskets from the battles of Trenton and Princeton
- Committee of Safety muskets, and Brown Bess
- Late War, the Southern Campaigns ending with Yorktown
- I would say the French 1763 or 1766 Charleville or a Brown Bess muskets
Brown Bess patterns would have been most likely Long Land from the Royal Colonial Armories,
Committee of Safety muskets, would have been locally made with little conformity between makers, based off of a list of specifications closely looking like a Brown Bess. Things like caliber, barrel length, bayonet lug & bayonet, locks would be very similar to an English round faced,
Older French musket from the F&I war such as the model 1728, were captured and given to the Colonial governments as reserve weapons for their armories, Some were kept by F&I Colonial troops and passed down or rebuilt by local gunsmiths,
Rifles are a more specific tool and more regionalized firearm of the period.
Fowlers or smoothbores, were also very regionalized. The are French, Dutch, and British styles. Western New York, Maine and Western PA may see more French styles. Eastern PA and New Jersey more English influence. The Hudson Valley and areas surround New York City Dutch.
So again, there is no one size fits all as there was nothing like a single War Department equipping units. Each State or Colony was responsible for equipping their units if possible. That is what makes the French Alliance so important, the French provide a logistical base to manufacture uniforms and arms that result in standardization in the Continental Army.
What I will say is if you are looking for a modern reproduction, stay away from the Indian or Pakistani pieces whish are not proofed. A Perdersoli Brown Bess or Charleville are acceptable representatives of period muskets. There are many fowlers and smoothbores out there, as well as rifles; but research is important as there is a lot of difference between an 19th century flintlock and a 18th century one.