I think a man named Pratt in Lexington was making rifles at that time.
Concord, maybe? From the text I linked:
PRATT, Alvan — Concord, Mass., gun maker, was born at Sherborn,
Mass., Nov. 23, 1790, and served his apprenticeship at the Whitte-
more gun factory in Sutton, Mass. After serving full time as
apprentice and some months as journeyman, went into business
with his brother Nathaniel, also a gunsmith, in Water town; how-
ever, they failed and Alvan returned to Sutton. His establish-
ment prospered for a while, then was burned out, after which he
returned to Concord, his birthplace, where he remained until his
death Jan. 20, 1877.
Pratt was well known for the accuracy of his rifles and excel-
lent quality of his products. However, being over-conservative,
if not actually old fashioned, he was opposed to improvements
and new machinery, and gradually his custom fell off and the
last ten years of his life were spent in repair work.
A musket lock-plate marked "A. PRATT" is described by
Mr. Walter White, which though converted to percussion shows
the characteristics of a Model 1795 musket. Certainly the arm is
of not later than 1808 vintage. In view of Alvan Pratt's birth
in 1790, it is not likely that he is the maker. An Asa Pratts
blacksmith, was located in Essex County, Mass., in 1756-1811.
There is no record known to date of Pratt contract.