NEW AR15 MOD HERE
https://www.nexusmods.com/morrowind/mods/51843

Tactical Morrowind V1.4

Weapons/armor/ammo are located in a crate next to the Seyda Neen census and exise office.
Weapons/armor/ammo are located in a crate in the tactical shooting range.

Enter COC "TACTICAL SHOOTING RANGE" in the console to access the shooting range.

I also recommend downloading these mods in  the following order to fix the missing ammunition in the Seyda Neen crate and add new firearms.
1.https://www.nexusmods.com/morrowind/mods/46926/
2.https://www.nexusmods.com/morrowind/mods/46926/
3.https://www.nexusmods.com/morrowind/mods/47076
4.https://www.nexusmods.com/morrowind/mods/47080
5.https://www.nexusmods.com/morrowind/mods/47081
6.https://www.nexusmods.com/morrowind/mods/47091
 
Firearm list
20MM R - 20 mm Currently uses 50 BMG as a placeholder
Remington 870 - Slug/Buckshot/Dart
ACR - 5.56
AK-47 - 5.45
AK-47 Custom - 5.45
AKS-74U - 5.45
AN-94 - 5.45
Colt ANACONDA - 44 magnum Currently uses 50 AE as a place holder
ARX160 - 5.56
AS Val - 9x39
AS50 - 50 BMG
AT4 - RPG
Steyr AUG - 5.56
Steyr AUG M203 - 5.56/40 mm
Artic Warfare Magnum - .338 lapua Currently uses 50 BMG as a placeholder
Desert Eagle - 50 AE
Desert Eagle Camo - 50 AE
Desert Eagle Scoped - 50 AE
Desert Eagle XIX - 50 AE
F2000 - 5.56
F2000 GL1 - 5.56/40 mm
F2000 Prototype 5.56/40 mm
F2000 Suppressor 5.56/40 mm
FAL - 7.62x51 Currently uses 308 as a placeholder
FAMAS - 5.56
FR-F2 - 7.62x51 Curently uses 308 as a place holder
G3SG1 - 7.62x51 Currently uses 308 as a place holder
G11 - 4.73×33mm caseless Currently uses 5.56 as a placeholder
G36 - 5.56
G36 AG36 - 5.56 /40 mm
G36K - 5.56
GTAR-21 - 5.56/40 mm
HK121 7.62x51 Currently uses 308 as a placeholder
Browning High Power - 9x19
KH2002 - 5.56
KRISS Vector 9x19/45 ACP
KSG-15 Slug/Buckshot/dart
L2A3 - 9x19
L85A1 - 5.56
L85A1 L123 - 5.56/ 40 mm
LR300 - 5.56
LR300 M203 - 5.56/ 40 mm
M3 - Slug/Buck/Dart
M4A1- 5.56
M4A1 Camo - 5.56
M4A1 FDE - 5.56
M14 EBR - 7.62x51Currently uses 308 as a placeholder
M16A1 - 5.56
M32 - 40 mm
M43 - 5.56
M60 - 7.62x51 Currently uses 308 as a placeholder
M92FS - 9x19
M95 - 50 BMG
M249 - 5.56
M700 - 308
M950 - 9x19
M950 Custom - 9x19
M1911 - 45 ACP
M2010 - .300 Winchester Magnum Currently uses 308 as a placeholder
MG36 - 5.56
MK3A1 Slug/Buck/Dart
MK23 - 45 ACP
MP7A1 -  4.6x30mm Currently uses 9x19 as a placeholder
NG7 - 5.56
Falcon OP99 - 50 BMG
P90 - 5.7x28mm
P90 Camo - 5.7x28mm
P90 Suppressor - 5.7x28mm
P99 - 9x19
PB - 9x18
PM - 9x18
PP19 Bizon - 9x19
PP-2000 - 9x19
PSG1 - 7.62x51 Currently uses 308 as a placeholder
PSG1 Camo - 7.62x51 Currently uses 308 as a placeholder
QBB-95 - 5.8×42mm Currently uses 5.56 as a placeholder
QBS-09 - Slug/Buckshot/Dart
QBZ-95 - 5.8×42mm Currently uses 308 as a placeholder
RG6 - VOG-25R
RPG7 - RPG
SCAR H - 7.62x51mm
SCAR L - 5.56
SG552 - 5.56
SL8 -  5.56
SR2 Veresk - 9x21 Currently uses 9x19 as a placeholder
SVD - 7.62x54mm
SVU - 7.62x54mm
TAR-21 - 5.56
TAR-21Laser - 5.56
TRG-42 - 7.62x51/308
ULTIMAX 100 - 5.56
USAS-12 - Slug/Buckshot/Dart
USAS-12 Camo - Slug/Buckshot/Dart
USP-45 - 45 ACP
UTS-15 - Slug/Buckshot/Dart
VSS Vintorez - 9x39
WA2000 - 7.62x51
XM8 - 5.56
XM8 FDE - 5.56
XM1014 - Slug/Buckshot/Dart
XM1014 FDE - Slug/Buckshot/Dart
XM1014 Wooden Furniture Slug/Buckshot/Dart
AR-556 - 5.56
MP5 - 9x19
Ingram M10 - 45 ACP
Benelli M4 - Slug/Buckshot/Dart
HSG-1 - Slug/Buckshot/Dart
MK14 Mod 0 EBR - 7.62x51 Currently uses 308 as a placeholder

Ammunition list
12G Dart
12G Shell
12G Slug
.300 AAC Blackout
308
40mm Grenade
40mm Incendiary Grenade
45 ACP
45 ACP Hydra Shok
50 AE
50 BMG
5.45×39mm
5.45×39mm AP
5.56×45mm
5.56×45mm AP
5.56×45mm Tracer
5.7×28mm
5.7×28mm AP
7.62x54mm
7.62x54mm 7N14
7.62x54mm AP
9x18mm
9x18mm +P+
9x19mm
9x19mm Hollow Point
9x39 PAB-9
9x39 SP-5
9x39 SP-6
VOG-25R
RPG

Upcoming for V1.5
Model improvements
More firearms
More ammo types
Improved shooting range
Fixed ammunition capacity
Optional weapon Magazines
Improved scripts
Improved sounds
Improved tracer effect
Balanced weapon statistics
Optional leveled list replacer