Based on MAME dumps here are all the confirmed versions of the games in this series:
-System NB1 w/V147 POSITION PCB 2421960102 (2421970102)
Gun Bullet (Japan, GN1)
Point Blank (World, GN2 Rev B, set 1)
Point Blank (World, GN2 Rev B, set 2)
Gun Bullet (US, GN3 Rev B)
-System 11 w/GUN I/F PCB 8645960701 (8645970701)
Point Blank 2 (World, GNB2/VER.A)
Point Blank 2 (World, GNB2/VER.A alt)
Point Blank 2 (US, GNB3/VER.A)
Point Blank 2 (Unknown region)
-System 12 w/GUN I/F A4111 PCB 8645960701 (8645970701)
Gunbarl (Japan, GNB4/VER.A)
Point Blank 2 (World, GNB5/VER.A)
Oh! Bakyuuun (Japan, OB1/VER.A)
Ghoul Panic (World, OB2/VER.A)
-System 10 w/EXIO PCB 8906960602 (8906970602)
Gunbalina (Japan, GNN1 Ver.A)
Point Blank 3 (World, GNN2 Ver.A)
System 11 and 12 share the same Gun IF board but nothing else is shared between them
based on the numbering scheme I'd guess there's an undumped System 11 version of "Gunbarl"
FWIW I own:
Point Blank (World, GN2 Rev B)
Point Blank 2 (World, GNB5/VER.A)
Ghoul Panic (World, OB2/VER.A)