Older, 90s era Bushmasters (some) were made by LAR (Grizzly) company.
LAR was one of 4 major receiver companies in the United States at the time that produced AR receivers for pretty much everyone else.
Noveske and Spikes also used LAR Grizzly, who at the time was also a small time defense manufacturer and was building top notch products. You can tell if your older Bushmaster is one of the original LAR guns, as the serial number will start with an L.
I have a couple LAR (Grizzly) billet uppers that are fantastic
