Changes:

Weapons:

9mm Pistol:
Renamed to: Browning Hi-Power
Fires Slightly Faster
Deals about 2 more damage
Deals 1 more critical damage

.357 Magnum:
Renamed to Colt Single-Action Army
Deals slightly more damage
Fires slightly faster
Stronger
Deals 2 more critical damage

.44 Magnum:
Renamed to: Smith & Wesson Model 29
Deals 3 more damage
Deals 2 more critical damage

9mm SMG:
Renamed to: M3 Grease Gun
Fires slightly faster
+2 Clip Size
+5 Health

5mm SMG(PN):
Renamed to: FN P90
Deals 1 more damage

12.7mm Pistol:
Renamed to:Sig Sauer 14
+4 Damage

.44 Pistol(PN):
Renamed to: Desert Eagle .44
+2 Damage

12.7mm SMG(It didn't exist so I made something up and now the gun is quite different.):
Renamed to: LZ SMG44
-3 Damage
Fires slightly Faster
+9 Clip Size
Chambered in .44 Magnum
Deals 4 more critical damage
+0.6 Weight

That Gun:
Renamed to: 2019 Detective Special
+14 Damage
+0.4 Weight
+38 Skill Requirement
+3100 Value
+1 Critical Damage
Fires faster
Chambered in .44 Magnum

Caravan Shotgun:
Renamed to: Winchester Model 101
Fires both shells at once (much like the S-OFF Shotgun)
+1 Damage

10mm Pistol:
Renamed to: N99
+2 Damage
+1 Clip Size

10mm SMG:
Renamed to: N108
+1 Damage

Hunting Revolver:
Renamed to: Big Frame
+1 Damage

Silenced .22LR Pistol:
Renamed to: Ruger 22/45
+1 Damage
+2 Clip Size

Silenced .22LR SMG:
Renamed to: American 180
+1 Critical Damage

Hunting Shotgun:
Renamed to: Remington 870
+4 Damage
Less accurate
Fires +2 pellets

Single Shotgun:
Renamed to: New England Firearms Pardner
+7 Damage

Lever-Action Shotgun:
Renamed to: Winchester 1887
+1 Damage

Riot Shotgun:
Renamed to: M37 Ithaca
+1 Damage
+2 Clip Size

Service Rifle:
Renamed to: AR-15
Automatic
+4 Clip Size
+1.2 Weight

Assault Carbine:
Renamed to: M4 Carbine
+1 Damage
+6 Clip Size

This Machine:
Renamed to: Old Reliable
+1 Damage
Chambered in 10mm

Battle Rifle(WMX):
Renamed to: M1 Garand
+1 Damage

Cowboy Repeater:
Renamed to: Winchester 1886
+4 Damage

Trail Carbine:
Renamed to: Marlin Model 336
+1 Damage

Chinese Pistol(PN):
Renamed to: C96 Mauser
+16 Clip Size
+2 Damage

Chinese Sniper Rifle(PN):
Renamed to: Dragunov SVD
+1 Damage
Chambered in 5.56mm

Chinese Assault Rifle(PN):
Renamed to: Type 93
+10 Clip Size
-1 Damage
Chambered in 10mm

Hunting Rifle:
Renamed to: Winchester Model 70
+1 Damage

Light Machine Gun:
Renamed to: FN Minimi
+1 Damage

Anti-Materiel Rifle:
Renamed to: HECATE-II
+15 Damage
+100 Health

European Battle Rifle(PN):
Renamed to: FN FAL
+2 Damage
+2 Clip Size

DB Shotgun(PN):
Renamed to: TOZ-66
+1 Damage

Sawed-Off Shotgun:
Renamed to: TOZ-66 S-OFF
+1 Damage

Big Boomer:
Renamed to:Boom Stick
+2 Damage
Fires one shell at once
Much faster firing speed

Varmint Rifle:
(Nobody likes the VR,so I made it into a BA Shotgun.)
Renamed to: Savage 220
+23 Damage
Much more spread
+16 Value
Chambered in 20 Gauge

Three-Shooter(PN):
Renamed to: Triple Threat S-OFF
Fires all 3 barrels at once (for a total of 243 DMG/Shot)
+1 Damage
Can score critical hits 
7 STR requirement
75 Guns requirement
Less accurate
+1 Weight
+2100 Value

Marksman Carbine:
Renamed to: Colt Model 933
+1 Damage
Automatic
+300 Value

Minigun:
Renamed to: Vulcan Minigun
+1 Damage
Fires 5 projectiles per shot

Grenade Rifle:
Renamed to: M79

Grenade Launcher:
Renamed to: ChinaLake

Ammunition:

12.7mm:
Renamed to: .50 Action Express

12.7mm HP:
(This isn't real,but it's much more fun to use than HP.)
Stats:
Renamed to:.50 Action Express,Expanded Case
0.75x Condition Wearing
1.3x Damage
Penetrates 15 DT
Costs 85 Caps/1 Round
Much heavier than standard 12.7mm round.

10mm JHP:
(It's better than JHP,I also didn't know .40 cal was actually shorter than 10mm auto at the time of making this..)
Stats:
Renamed to: .40 S&W
Heavier than normal 10mm
1.2x Damage
0.80x Condition Wearing
0.35x Spread
Costs 11 Caps/1 Round

.50 MG:
Stats:
Renamed to: .50 BMG

9mm +P
(It's sort of realistic,but it's better than +P IMO)
(If you were to shoot a .38 inside of a 9mm pistol it would still fire,just not eject the casing..)
Stats:
Renamed to: .32 ACP (This was an error on my part,it's supposed to be .38 ACP.)
0.75x Condition Wearing
0.90x Damage
Weighs a bit less than regular 9mm
Costs 5 Caps/1 Round