Familiarity

The timeframe that Funny New Guys is set is 1967.

That sets some important points for weaponry.

It means all the "work" I did looking up Blooper stuff is still relevant and the more familiar M203 won't be on the scene yet.  The XM148 has started field trials.

It also amends my list of available rounds:

See High Tech p.143 and p.145 and SEALs in Vietnam p.33 for stats.

M381 HE (1967) - 3 yard min distance. 32g Comp-B. 0.503 lb.

M406 HE (1967) - 15 yard min distance. 32g Comp-B. 0.503 lb.

M576 MP (Multi-Projectile) (1967) - No min distance. 20 #4 Buckshot pellets. 0.254 lb.

M585 White Star Flare (1967) - 330 yard min distance, 7 sec, 55,000 candela. 0.41 lb.

M651 Riot Control CS tear gas (1967) - 33 yard min distance, 6.5 yard sphere, 20 sec burn time. 0.45 lb.

M676 Yellow Smoke (1967) - 150 yd. min distance. 90 sec burn time. 0.48 lb.

M680 White Smoke (1967) - 150 yd. min distance. 90 sec burn time. 0.48 lb.

M682 Red Smoke (1967) - 150 yd. min distance. 90 sec burn time. 0.48 lb.

I should also note that the date I've shown is just the earliest reference I have for the round in question.  Some of them must pre-date that because the M79 is first fielded in 1961.

That makes my infantry weapons list:

M16A1 rifle (XM16E1?)
M60 machine gun
M79 grenade launcher
M1911A1 pistol (but I'm amused to change that to M4...)
M26 (lemon) and M33 (baseball) are the common fragmentation grenades.