To Rename the gun to Pit Viper, go to the strings.gxt2 file in your 1899 firearms folder and go to "Weapon_pistol_m1899 = [something]" and replace whatever that [something] is with "Pit Viper"




To Add accurate weapon stats to the gun, you're gonna need to find the weapons.ymt in your 1899 firearms folder and then search for the "CWeaponInfo" for "weapon_pistol_m1899" and replace the whole entry with :

                <Item type="CWeaponInfo">
                    <Properties />
                    <Name>WEAPON_PISTOL_M1899</Name>
                    <Model />
                    <SwapClipSetHash />
                    <GripClipSetHash />
                    <GripClipHash />
                    <Audio>0xA9A481CF</Audio>
                    <Slot>slot_pistol_m1899</Slot>
                    <FireType>BULLET</FireType>
                    <Group>GROUP_PISTOL</Group>
                    <WeaponType>Shortarm</WeaponType>
                    <SwapWeaponType>Weapon_Shortarm</SwapWeaponType>
                    <Score value="340" />
                    <UNK_MEMBER_0x9A862BD2 value="-1" />
                    <AnimationLookupHash>WEAPON_PISTOL_M1899</AnimationLookupHash>
                    <DamageModes>
            <Item>
              <AmmoInfo>AMMO_45_ACP</AmmoInfo>
              <Name>DM_45_ACP</Name>
              <ClipIndex value="0"/>
              <Damage value="32.01850000"/>
              <DamageType>BULLET</DamageType>
              <Penetration value="12.00000000"/>
              <Explosion>
                <Default>EXP_TAG_DONTCARE</Default>
              </Explosion>
              <AccuracyInfo>ACC_45_ACP_M1911</AccuracyInfo>
              <DamageFallOffInfo>DF_45_ACP_M1911</DamageFallOffInfo>
              <RecoilShakeAmplitude value="2.17050000"/>
              <RecoilShakeAmplitudeFirstPerson value="2.17050000"/>
              <MeleeExecutionDismemberment value="0.00000000" />
              <DismembermentRanges> <!-- DISMEMBERMENT 45 ACP M1911 -->
                <Item>
				  <MaxRange value="2.00000000" />
				  <DismembermentPercent value="0.00000000" />
				  <DismembermentIncrement value="1" />
				</Item>
				<Item>
				  <MaxRange value="8.23600000" />
				  <DismembermentPercent value="0.00000000" />
				  <DismembermentIncrement value="1" />
				</Item>
				<Item>
				  <MaxRange value="12.50000000" />
				  <DismembermentPercent value="0.00000000" />
				  <DismembermentIncrement value="1" />
				</Item>
				<Item>
				  <MaxRange value="17.80000000" />
				  <DismembermentPercent value="0.00000000" />
				  <DismembermentIncrement value="1" />
				</Item>
			  </DismembermentRanges>
            </Item>
                    </DamageModes>
                    <AimingInfo>AIMING_1H</AimingInfo>
                    <UNK_MEMBER_0x6D43951C>
                        <Item>
                            <Type>0x38ED1366</Type>
                            <Size value="21" />
                            <BulletsPerAnimLoop value="21" />
                        </Item>
                    </UNK_MEMBER_0x6D43951C>
                    <UNK_MEMBER_0x16FED869 />
                    <AccuracyInfo>SAA_45SW</AccuracyInfo>
                    <DamageFallOffInfo>DAMAGE_FALLOFF_REPEATER_WINCHESTER_44_40</DamageFallOffInfo>
                    <WeaponHeadShotDistance>
                        <MinHeadShotDistanceAI value="0.00" />
                        <MaxHeadShotDistanceAI value="99999.00" />
                        <MinHeadShotDistancePlayer value="0.00" />
                        <MaxHeadShotDistancePlayer value="99999.00" />
                        <MaxHeadShotDistanceToPlayerWithScope value="99999.00" />
                    </WeaponHeadShotDistance>
                    <WeaponDamageModifiers>
                        <HeadShotDamageModifierAI value="5.00" />
                        <HeadShotDamageModifierPlayer value="5.00" />
                        <NonRegionLimbDamageModifier value="0.001" />
                        <LightlyArmouredDamageModifier value="1.00" />
                        <HeadOnCloseRangePedModifier value="1.00" />
                        <UNK_MEMBER_0x1806425C value="1.00" />
                        <CriticalHitChanceModifier value="1.00" />
                        <VehicleDamageModifier value="1.00" />
                        <PlayerDamagedByAIModifier value="1.00" />
                        <AIDamagedByPlayerModifier value="1.00" />
                    </WeaponDamageModifiers>
                    <WeaponDamageTime>
                        <DamageTime value="0.0" />
                        <DamageTimeInVehicle value="0.0" />
                        <DamageTimeInVehicleHeadShot value="0.0" />
                    </WeaponDamageTime>
                    <!--FN1900-->
                    <WeaponForce>
                        <Force value="155.95" />
                        <ForceHitPed value="22.95" />
                        <ForceHitVehicle value="22.95" />
                        <ForceHitFlyingHeli value="22.95" />
                        <OverrideForces />
                        <ForceMaxStrengthMult value="1.00" />
                        <ProjectileForce value="1.00" />
                    </WeaponForce>
                    <MeleeExecutionDismemberment value="1.0" />
                    <DismembermentRanges />
                    <DismembermentSetting>DISMEMBERMENT_DEFAULT</DismembermentSetting>
                    <StaminaDrainPrimedModifier value="0.5" />
                    <FragImpulse value="129.00" />
                    <VerticalLaunchAdjustment value="0.0" />
                    <LaunchPitchCorrectionMax value="90.00" />
                    <DropForwardVelocity value="32.00" />
                    <Speed value="905.00" />
                    <MaxDrawingMBR value="-1.0" />
                    <BatchSpread value="0.000" />
                    <WeaponReload>
                        <ReloadTime value="-1.0" />
                        <VehicleReloadTime value="-1.0" />
                        <AnimReloadRate value="1.00" />
                        <SectionedReloadInfo>R_RELOAD_M1899</SectionedReloadInfo>
                        <SectionedReloadInfoDual>R_DUAL_PISTOL_M1899</SectionedReloadInfoDual>
                    </WeaponReload>
                    <CockingInfo>COCKING_PISTOL_M1899</CockingInfo>
                    <UNK_MEMBER_0x20D873DC />
                    <IkRecoilInfo>RECOIL_VOLCANIC</IkRecoilInfo>
                    <QuiverInfo />
                    <WeaponTimeBetweenShots>
                        <TimeBetweenShotsMin value="0.10" />
                        <TimeBetweenShotsMax value="0.10" />
                        <TimeLeftBetweenShotsWhereShouldFireIsCached value="-1.0" />
                        <SpinUpTime value="0.0" />
                        <SpinTime value="0.0" />
                        <SpinDownTime value="0.0" />
                        <AlternateWaitTime value="-1.0" />
                    </WeaponTimeBetweenShots>
                    <WeaponBulletBending/>
                    <Vfx>
                        <EffectGroup>WEAPON_EFFECT_GROUP_PISTOL_SMALL</EffectGroup>
                        <VfxBloodInfoHashName>0x0CD20495</VfxBloodInfoHashName>
                        <VfxBloodMeleeInfoHashName>0x9E5C1353</VfxBloodMeleeInfoHashName>
                        <VfxBloodPoolInfoHashName>0x13585F5E</VfxBloodPoolInfoHashName>
                        <VfxWeaponImpactAmmoInfoHashName>IMPFX_REV</VfxWeaponImpactAmmoInfoHashName>
                        <VfxWeaponImpactAmmoStrengthEvo value="0.129" />
                        <VfxWeaponImpactMeleeInfoHashName>0xE94B7E71</VfxWeaponImpactMeleeInfoHashName>
                        <VfxWeaponImpactMeleeStrengthEvo value="0.140" />
                        <VfxWeaponMuzzlePositionOverride x="0.068" y="0.0" z="0.0" />
                        <VfxWeaponMuzzleFlashInfoHashName>GUNFX_SMOKELESS</VfxWeaponMuzzleFlashInfoHashName>
                        <VfxWeaponMuzzleSmokeInfoHashName />
                        <VfxWeaponBarrelSmokeInfoHashName />
                        <VfxWeaponHammerInfoHashName />
                        <VfxWeaponTracerInfoHashName>0x0C0B70A6</VfxWeaponTracerInfoHashName>
                        <VfxWeaponShellInfoHashName>PISTOL_SHELL</VfxWeaponShellInfoHashName>
                        <VfxWeaponGroundDisturbInfoHashName>0x4C0A490A</VfxWeaponGroundDisturbInfoHashName>
                        <VfxWeaponInteriorSmokeInfoHashName />
                        <VfxWeaponAirDebrisInfoHashName></VfxWeaponAirDebrisInfoHashName>
                    </Vfx>
                    <WindDisturbance>
                        <WindDisturbanceMuzzleInfoHashName>0xC9A04EB7</WindDisturbanceMuzzleInfoHashName>
                        <WindDisturbanceBulletInfoHashName>0x300807A5</WindDisturbanceBulletInfoHashName>
                    </WindDisturbance>
                    <DegradationInfo>DEGRADATION_PISTOL_SL</DegradationInfo>
                    <FamiliarityInfo>FAMILIARITY_PISTOL</FamiliarityInfo>
                    <RumbleInfo>RUMBLE_PISTOL_M1899</RumbleInfo>
                    <WeaponRanges>
                        <LockOnRange value="50.00" />
                        <LockOnRangeInVehicle value="50.00" />
                        <IdleLockOnRangeModifier value="1.00" />
                        <SoftLockDurationOverride value="-1.0" />
                        <WeaponRange value="9999.00" />
                        <WeaponRangeInVehicle value="9999.00" />
                        <MeleeWeaponRangeMin value="1.50" />
                        <MeleeWeaponRangeMax value="2.00" />
                        <MeleeWeaponRangeMaxRun value="4.00" />
                        <MeleeWeaponRangeMinToRun value="20.00" />
                        <DesiredRange value="25.00" />
                        <ProjectileRangeMin value="-1.0" />
                        <ProjectileRangeMax value="-1.0" />
                        <AiSoundRange value="100.0" />
                        <AiPotentialBlastEventRange value="-1.0" />
                    </WeaponRanges>
                    <BulletDirectionOffsetInDegrees value="90.00" />
                    <UNK_MEMBER_0xC824F688 value="1.00" />
                    <IsSpecialWeapon value="TRUE" />
                    <IsOutlawWeapon value="false" />
                    <UnlockWeaponHash>WEAPON_REVOLVER_CATTLEMAN</UnlockWeaponHash>
                    <BrokenWeaponHash />
                    <VehicleWeaponHash />
                    <WeaponCamera>
                        <CameraDictionaryHash />
                        <DefaultCameraHash>SHOTGUN_AIM_CAMERA</DefaultCameraHash>
                        <InteractionLockonCameraHash>0x5D3DEFD9</InteractionLockonCameraHash>
                        <AimCameraHash />
                        <FireCameraHash />
                        <HorseCameraHash>0x65B60988</HorseCameraHash>
                        <CoverCameraHash>0xC4E1F206</CoverCameraHash>
                        <CoverReadyToFireCameraHash>0x0797BD96</CoverReadyToFireCameraHash>
                        <CoverHipFireCameraHash>0x0797BD96</CoverHipFireCameraHash>
                        <RunAndGunCameraHash>DEFAULT_THIRD_PERSON_PED_RUN_AND_GUN_CAMERA</RunAndGunCameraHash>
                        <CinematicShootingCameraHash />
                        <GrappleCameraHash>DEFAULT_FOLLOW_PED_CAMERA</GrappleCameraHash>
                        <CameraFov value="55.00" />
                        <FirstPersonAimFovMin value="73.00" />
                        <FirstPersonAimFovMax value="73.00" />
                        <FirstPersonDofSubjectMagnificationPowerFactorNear value="1.03" />
                        <FirstPersonDofMaxNearInFocusDistance value="0.0" />
                        <FirstPersonDofMaxNearInFocusDistanceBlendLevel value="0.30" />
                        <RecoilShakeHash>FPS_SHOTGUN_RECOIL_SHAKE</RecoilShakeHash>
                        <RecoilShakeHashFirstPerson>FPS_SHOTGUN_RECOIL_SHAKE</RecoilShakeHashFirstPerson>
                        <AccuracyOffsetShakeHash>0x2C8D988E</AccuracyOffsetShakeHash>
                        <MinTimeBetweenRecoilShakes value="0" />
                        <RecoilShakeAmplitude value="1.00" />
                        <RecoilShakeAmplitudeFirstPerson value="1.00" />
                        <ExplosionShakeAmplitude value="-1.00" />
                    </WeaponCamera>
                    <CoverTypeHash>SHORTARMS</CoverTypeHash>
                    <UNK_MEMBER_0x239BF1C9>WEAPON_PISTOL_M1899</UNK_MEMBER_0x239BF1C9>
                    <!--FN1900-->
                    <WeaponReticule>
                        <ReticuleHudPosition x="0.50" y="0.50" />
                        <ReticuleStyleHash>PISTOL</ReticuleStyleHash>
                        <FirstPersonReticuleStyleHash>PISTOL</FirstPersonReticuleStyleHash>
                        <ReticleSwaySettleDuration value="300" />
                        <ReticleSwayPostSettleRestartTime value="300"  />
                        <ReticleSwayAmplitudeModifierNear value="0.01034"  />
                        <ReticleSwayAmplitudeModifierFar value="0.02067" />
                        <ReticleSwayRangeNear value="0.00" />
                        <ReticleSwayRangeFar value="150.00" />
                    </WeaponReticule>
                    <WeaponAimOffsets>
                        <AimOffsetMin x="0.20" y="-0.025" z="0.40" />
                        <AimOffsetMax x="0.275" y="-0.05" z="0.525" />
                        <TorsoAimOffset x="-1.00" y="0.55" />
                        <TorsoCrouchedAimOffset x="0.20" y="0.05" />
                        <AimProbeLengthMin value="0.40" />
                        <AimProbeLengthMax value="0.375" />
                        <AimOffsetMinFPSIdle x="0.00" y="0.00" z="0.00" />
                        <AimOffsetMedFPSIdle x="0.50" y="0.50" z="0.50" />
                        <AimOffsetMaxFPSIdle x="1.00" y="1.00" z="1.00" />
                        <AimOffsetMinFPSLT x="0.00" y="0.00" z="0.00" />
                        <AimOffsetMaxFPSLT x="1.00" y="1.00" z="1.00" />
                        <AimOffsetMinFPSRNG x="0.00" y="0.00" z="0.00" />
                        <AimOffsetMaxFPSRNG x="1.00" y="1.00" z="1.00" />
                        <AimOffsetMinFPSScope x="0.00" y="0.00" z="0.00" />
                        <AimOffsetMaxFPSScope x="1.00" y="1.00" z="1.00" />
                        <AimOffsetEndPosMinFPSIdle x="0.00" y="0.00" z="0.00" />
                        <AimOffsetEndPosMedFPSIdle x="0.50" y="0.50" z="0.50" />
                        <AimOffsetEndPosMaxFPSIdle x="1.00" y="1.00" z="1.00" />
                        <AimOffsetEndPosMinFPSLT x="0.00" y="0.00" z="0.00" />
                        <AimOffsetEndPosMedFPSLT x="0.50" y="0.50" z="0.50" />
                        <AimOffsetEndPosMaxFPSLT x="1.00" y="1.00" z="1.00" />
                        <AimProbeRadiusOverrideFPSIdle value="0.00" />
                        <AimProbeRadiusOverrideFPSIdleStealth value="0.00" />
                        <AimProbeRadiusOverrideFPSLT value="0.00" />
                        <AimProbeRadiusOverrideFPSRNG value="0.00" />
                        <AimProbeRadiusOverrideFPSScope value="0.00" />
                    </WeaponAimOffsets>
                    <WeaponIkOffset>
                        <LeftHandIkOffset x="0.00" y="0.00" z="0.00" />
                        <IkRecoilDisplacement value="40.00" />
                        <IkRecoilDisplacementScope value="1000.00" />
                        <IkRecoilDisplacementScaleBackward value="40.00" />
                        <IkRecoilDisplacementScaleVertical value="50.40" />
                        <UpperArmTranslationBias value="0.00" />
                    </WeaponIkOffset>
                    <PickupHash>PICKUP_WEAPON_PISTOL_M1899</PickupHash>
                    <MovementModeConditionalIdle />
                    <StatName>PS_M1899</StatName>
                    <SkillStatName />
                    <WeaponNM>
                        <KnockdownCount value="10" />
                        <KillshotImpulseScale value="0.10" />
                        <NmShotTuningSet>NORMAL</NmShotTuningSet>
                        <NmHeadShotTuningSet>HEADSHOT</NmHeadShotTuningSet>
                        <NmNeckShotTuningSet>NECKSHOT</NmNeckShotTuningSet>
                        <NmChestShotTuningSet>CHESTSHOT</NmChestShotTuningSet>
                        <NmBackShotTuningSet>BACKSHOT</NmBackShotTuningSet>
                        <NmArmShotTuningSet>ARMSHOT</NmArmShotTuningSet>
                        <NmLegShotTuningSet>LEGSHOT</NmLegShotTuningSet>
                    </WeaponNM>
                    <PrimaryHandBlackboardString>RIGHT_HAND_SMALL</PrimaryHandBlackboardString>
                    <SupportingHandBlackboardString />
                    <SecondaryHandBlackboardString>LEFT_HAND_SMALL</SecondaryHandBlackboardString>
                    <AttachPoints>
                        <Item>
                            <AttachBone>WAPGRIP</AttachBone>
                            <Components>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP</Name>
                                    <Default value="true" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_IRONWOOD</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_BURLED</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_PEARL</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_EBONY</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_ANTLER</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_IVORY</Name>
                                    <Default value="false" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_GRIP_BONE</Name>
                                    <Default value="false" />
                                </Item>
                            </Components>
                        </Item>
                        <Item>
                            <AttachBone>WAPCLIP</AttachBone>
                            <Components>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_CLIP</Name>
                                    <Default value="true" />
                                </Item>
                            </Components>
                        </Item>
                        <Item>
                            <AttachBone>WAPBARREL</AttachBone>
                            <Components>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_BARREL_SHORT</Name>
                                    <Default value="true" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_BARREL_LONG</Name>
                                    <Default value="false" />
                                </Item>
                            </Components>
                        </Item>
                        <Item>
                            <AttachBone>WAPSIGHT1</AttachBone>
                            <Components>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_SIGHT_NARROW</Name>
                                    <Default value="true" />
                                </Item>
                                <Item>
                                    <Name>COMPONENT_PISTOL_M1899_SIGHT_WIDE</Name>
                                    <Default value="false" />
                                </Item>
                            </Components>
                        </Item>
                    </AttachPoints>
                    <FireProbeBone>ID_SKEL_ROOT</FireProbeBone>
                    <!--PISTOL_M1899-->
                    <WeaponFlags> HasDropPrompt DoesRevivableDamage AllowCloseQuarterKills DelayedFiringAfterAutoSwap DontSwapWeaponIfNoAmmo NoWheelStats HasLowCoverReloads EnforceAimingRestrictions EnforceFiringAngularThreshold UseFPSAnimatedRecoil UseLegDamageVoice PlayOutOfAmmoAnim CarriedInHand Gun ApplyBulletForce CanLockonOnFoot CanLockonInVehicle CanFreeAim AnimReload UsableInCover UsableOnFoot UsableClimbing HasLowCoverSwaps OnlyFireOneShot OnlyFireOneShotPerTriggerPress UseFPSAimIK CanHipFire HasIronSight ForceEjectShellAfterFiring  NoLeftHandIK 0x5A3E5EDA 0xE8C586DD 0x75138DBF 0x6F3B1D01   0xCE1E0473  0x1FCE1778 0x081F0BDD 0xC6550BE0 0x1FE95B8B 0xDCF43CF3 0x42D5F625 0x40B6CD20 0xD250DFDB  0x46B4F2E8 UseGravityAfter 0x27895875 0x323DB9E4 0xD62ED034 0xF0F89FD8 0x75138DBF            0x6F3B1D01            0xD250DFDB </WeaponFlags>
                    <DefaultAIAttackMode>Shoot</DefaultAIAttackMode>
                    <AIAttackModes>Shoot</AIAttackModes>
                    <TintSpecValues>TINT_DEFAULT</TintSpecValues>
                    <FiringPatternAliases>FIRING_PATTERN_PISTOL</FiringPatternAliases>
                    <ReloadUpperBodyFixupExpressionData>DEFAULT</ReloadUpperBodyFixupExpressionData>
                    <WeaponAdditiveWeight>
                        <AimingBreathingAdditiveWeight value="2.00" />
                        <FiringBreathingAdditiveWeight value="2.00" />
                        <StealthAimingBreathingAdditiveWeight value="0.50" />
                        <StealthFiringBreathingAdditiveWeight value="0.50" />
                        <AimingLeanAdditiveWeight value="1.00" />
                        <FiringLeanAdditiveWeight value="1.00" />
                        <StealthAimingLeanAdditiveWeight value="0.50" />
                        <StealthFiringLeanAdditiveWeight value="0.50" />
                    </WeaponAdditiveWeight>
                    <DistanceFromTargetToSlideToDefaultLockOnBoneMin value="0.0" />
                    <DistanceFromTargetToSlideToDefaultLockOnBoneMax value="0.0" />
                    <ExpandPedCapsuleRadius value="0.0" />
                    <MeleeAnimPlaybackRate x="1.00" y="1.50" />
                    <AudioCollisionHash />
                    <HolsterAttachPoint>WEAPON_ATTACH_POINT_PISTOL_R</HolsterAttachPoint>
                    <AlternateHolsterAttachPoint>WEAPON_ATTACH_POINT_PISTOL_L</AlternateHolsterAttachPoint>
                    <MutuallyExclusiveHolsterAttachPoint>WEAPON_ATTACH_POINT_INVALID</MutuallyExclusiveHolsterAttachPoint>
                    <MutuallyExclusiveAlternateHolsterAttachPoint>WEAPON_ATTACH_POINT_INVALID</MutuallyExclusiveAlternateHolsterAttachPoint>
                    <ArmpitAttachPoint>WEAPON_ATTACH_POINT_INVALID</ArmpitAttachPoint>
                    <TemporaryAttachPoint>WEAPON_ATTACH_POINT_INVALID</TemporaryAttachPoint>
                    <ShortArmHolsterDOF value="1.00" />
                    <WeaponDualWieldAccuracyMod>
                        <PairedWithPistolAccuracyModifier value="0.75" />
                        <PairedWithRevolverAccuracyModifier value="0.75" />
                        <PairedWithShotgunAccuracyModifier value="0.65" />
                    </WeaponDualWieldAccuracyMod>
                    <LightRadiusMult value="1.00" />
                    <LightRadiusMultLerpTime value="0.0" />
                    <VehicleAttackAngle value="25.00" />
                    <MaxDeadeyeTaggedTargets value="99999" />
                    <TorsoIKAngleLimit value="-1.0" />
                    <MeleeRightFistTargetHealthDamageScaler value="-1.0" />
                    <AirborneAircraftLockOnMultiplier value="1.0" />
                    <UNK_MEMBER_0xC0AD3F0C />
                    <Caliber>0xDC8A28AF</Caliber>
                    <VertData>VERTDATA_PISTOL_M1899</VertData>
                    <MotivationImpactMultiplier value="1.00" />
                    <LookingGlassDefaultScopeInfo />
                </Item>
