The results are in!
https://orchidadvisors.com/top-30-largest-usa-firearm-manufacturers-of-2023/

The top US pistol manufacturers for 2023 are:

1) SIG Sauer - 944,562
2) Smith & Wesson - 604,696
3) Ruger - 505,735
4) Glock - 345,119
5) Springfield - 177,331

The ATF Annual Firearms Manufacturing and Exportation Report (AFMER) documents the number of firearms produced in the United States and sold worldwide.
https://www.atf.gov/resource-center/data-statistics