The interiors of the VFW post were shot on location at a real VFW hall in Grand Prairie, Texas (specifically Post #2494). Several of the hall's real veterans appear as extras in the bar during the opening scenes.
At 01:08:12, Boz (Travis Hammer) says "Fire it up". This was a chant by T-Bird (David Patrick Kelly) and his crew in The Crow (1994).
On the list of features seen above the cinema, one of them is called Bliss (2019), a reference to Begos' previous film.
Although it's never spoken onscreen, Walter's army jacket- and the end credits- indicate that his surname is "Reed," a reference to Walter Reed National Military Medical Center, one of the United States' most prominent military hospitals.
All the gore f/x were done practically.