Here are ideas for Antique Equivalents of LBB4 weapons - based on world.guns.ru - I've tried to match length, weight, caliber and configuration (i.e. bulpup or not) as much as possible.
Assault Rifle: M4 (though a bit lighter than the LBB4 AR),
XM8 (still light but looks like a "space gun"),
FN SCAR (almost a perfect match),
AKS-74U (a bit short but still in the range),
AKM (very similar in all aspects except for caliber),
Galil SAR (a bit too heavy),
SA Vz.58 (different caliber) and
G36K (almost a perfect match).
Advanced Combat Rifle: The best candidate is probably the
G11 despite the different caliber and not the Flechette-centric "
ACR"; is there any 9mm "assault rifle" around anyway, or should we wait to TL10? Anyway, the
F2000 and the
Tavor TAR-21 do have the "ACR looks", even though internally they are closer to the Assault Rifle category.
Light Assault Gun: This seems like a sniper rifle of sorts, though the 20mm caliber is quite big for a rifle (as opposed to a grenade launcher); a heavy sniper rifle which might look similar is the
Falcon.
Light Machine Gun: Minimi Standard Model,
Negev (though a bit heavy and capable of loading a box magazine as well as the belt), or the
RPK-74 (almost a perfect match; could load a box magazine as well as the belt).
Early Grenade Launcher: HK-69, or the
M79.
Auto-Grenade Launcher: AGS-30,
QLZ-87,
GMG,
Mk.19 and the
Mk.47.
