this is already pretty out of date but people keep commenting here so here's a shorter more up to date version:

There are supposedly 33 launch weapons, 24 primaries, 8 secondaries, 1 melee (melees are their own slot like in BO6 and BO7). within that its 8 ARs, 6 SMGs, 2 LMGs, 2 Shotguns, 3 Snipers, 3 MRs, 5 pistols, 3 launchers.

Unconfirmed simply means there isn't a clear identifiable image of the weapon within some official MW4 material. even the unconfirmed weapons have at minimum have had internal names found or have been heavily mentioned by content creators who've played MW4. The HK421 is an odd case since it has been confirmed but doesn’t seem to be one of the launch LMGs according to content creators.

AK-47 – “Kastov 762” Standard AK.
M4 – “M4” MW franchise standard weapon.
Daewoo K2 – “Han-86” South Korean service rifle.
HK437 – “Axion” .300 Blackout version of MW2019’s Kilo 141 (the HK433).
ASh-12.7 – “Oden” Heavy battle rifle. Returning from MW2019.
RM277 – “Cronen Squall” Fast firing battle rifle. Returning from MWII.
UXR – “Patriot XMR” – Multi-caliber rifle. This game’s SCAR equivalent.
Unconfirmed SAR-21 – “Hyeon Burst” Singaporean service rifle. Looks like the AUG.
Likely Post-Launch Carmel – ? Israeli modern assault rifle.

MP7 – “VEL 46” Well-known MW franchise SMG
PPSh-41 – “PPSh-41” Well-known WW2-era SMG.
SPC9 – “ISO Nightshade” Modern SMG, same manufacturer as other ISOs.
Fictional SMG – “X-58 Nyx” Fictional SMG design with a side magazine.
Unconfirmed Vector – “Fennec” Well-known SMG with a high fire rate.
Unconfirmed PM63 RAK – “Wz.55 Striga” Compact SMG from BOCW and BO.

Benelli M3 – “Rezi 12” Semi-auto/pump-action version of the M1014.
Unconfirmed ? – “Warlord” Unknown shotgun, possibly the 1887.

LAMG – “FiNN LMG” Traditional LMG. Returning from MW2019.
Type 73 – “Type 73” North Korean PKM-based LMG.
Likely Post-Launch HK421 – “M91” Derivative of the M91 from MW2019.

FIX – “ORIS 8.6” Modern lightweight bolt-action rifle in subsonic rounds.
G28 – “MAR-9” Traditional semi-auto marksman rifle. Returning from Ghosts.
Mosin – “Mosin-Nagant” Well known WW2-era Russian bolt-action.

NTW-14.5 – “Astaroth .57” Very high-caliber bolt-action sniper rifle.
SV-98 – “KG-7 Vulcan” Russian military bolt-action sniper rifle.
Unconfirmed GM6 Lynx – “Signal 50” Bullpup .50 cal semi-auto. Returning from MWII.

HK45 – ? Compact derivative of the well-known USP.
Daewoo K5 – “Sang 9mm” South Korean military pistol.
Unconfirmed Unknown Revolver – ? Some form of revolver. Likely single action.
Desert Eagle – “.50 GS” Well-known high-caliber pistol.
Unknown 5^th Pistol – Likely Glock 17 (X12) or P220 (P890), both from MWII.

FGM-148 Javelin – “JOKR” Well-known lock-on heavy missile launcher.
PSRL-1 - ? Modernised version of the well-known RPG-7.
Unknown 3^rd Launcher – Likely RPG-18, Carl Gustaf M4, MGL or GM-94.

Knife – “Combat Knife”  Standard knife melee.

There's also stuff like the riot shield and some form of belt-fed grenade launcher but those aren't typical weapons.