I don't know why the projectiles are not mentioned in any official classlist. They can be useful for weapon tests , mine/arty scripting , etc.
Here is an example for usage and the list of some projectile types for IF44.

Example on a Panzerschreck rocket propelled grenade:
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projectile1="lib_r_88mm_rpzb" createvehicle position trigger1; /(a rpg with name "projectile1" will be generated at a trigger with name "trigger1")
projectile1 setpos [(getpos projectile1 select 0),(getpos projectile1 select 1),3]; /(in this case the generated projectile's height will be set at 3m above the ground , from where it will start)
projectile1 setdir 0; /(direction of generated projectile , seem not really to work with heavy gun projectiles.)
projectile1 setvelocity [0,110,10]; /(the speed in m/s is here in the second entry , bullets need the first entry for m/s *i don't know why , and the third entry is direction/angle (?),-i'm not really sure , but it significantly changes shooting angle)
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List of IF44 projectiles:
-----------------------------------------------------
  • B_9X19_Ball -(MP40,P38)
  • B_762X25_Ball -(PPSh41,M1895,TT33)
  • B_762X54_Ball -(DP28,DT)
  • B_762X54_Ball_NoCartridge -(M91/30)
  • B_792X57_Ball -(MG42)
  • B_792X57_Ball_NoCartridge -(K98k)
  • B_792X33_Ball -(StG44)
  • B_127X99_Ball -(M2)
  • B_127X99_Ball_noTracer -(M2)
  • LIB_8Rnd_81mmHE_GRWR34 - (GrWr34-Magazine)
  • LIB_8Rnd_82mmHE_BM37 - (BM37-Magazine)
  • LIB_Sh_81_HE -(GrWr34)
  • LIB_Sh_82_HE -(BM37)
  • B_23mm_AA -(Flak38) *seems that they took russian 23mm from Arma2 as projectile for the 20mm
  • B_37mm_AA -(61k)

-----------------
T34/85 & Su-85
  • LIB_BR365_AP
  • LIB_BR365P_APCR
  • LIB_O365_HE

------------------------------
T34/76
  • LIB_BR350B_AP
  • LIB_BR350P_APCR
  • LIB_OF350_HE

----------------------------------
JS-2
  • LIB_D25T_AP
  • LIB_D25T_HE

-----------------------------
ZIS-3
  • LIB_BR350B_AP
  • LIB_BR350P_APCR
  • LIB_OF350_HE

------------------------------
PaK40
  • LIB_PzGr39_KWK40_AP
  • LIB_PzGr40_KWK40_APCR
  • LIB_SprGr34_KWK40_HE

----------------------------------
StuGIII
  • LIB_PzGr39_KWK40_AP
  • LIB_PzGr40_KWK40_APCR
  • LIB_SprGr34_KWK40_HE
-----------------------------------
PzIV
  • LIB_PzGr39_KWK40_AP
  • LIB_PzGr40_KWK40_APCR
  • LIB_SprGr34_KWK40_HE

------------------------------------
PzV
  • LIB_PzGr3942_KwK42_AP
  • LIB_PzGr4042_KwK42_APCR
  • LIB_SprGr42_KwK42_HE

-------------------------------------
PzVIb
  • LIB_PzGr43_AP
  • LIB_PzGr40_APCR
  • LIB_SprGr39_HE

Explosions

  • LIB_boom
  • LIB_boom_PP
  • LIB_boom_TMI42
  • LIB_boom_Ladung_Small
  • LIB_boom_Ladung_Big
  • LIB_boom_SMI_35
  • LIB_boom_pomzec
  • LIB_boom_STMI
  • LIB_boom_shumine42
  • LIB_boom_m3
  • LIB_boom_PMD6
  • LIB_boom_TM44
  • LIB_boom_TROTIL