For those saying it doesn't work it does just go to
update/update.rpf/common/data/ai and edit weaponanimation...code is as described for the desired weapon.
You can CTRL+F and search franklin and copy and paste the code under his name. The only known issue is when shooting the first initial shot the weapon fires twice. Here's the Code, Be Eazy.

<Item key="WEAPON_PISTOL">
<CoverMovementClipSetHash />
<CoverMovementExtraClipSetHash />
<CoverAlternateMovementClipSetHash>cover@move@ai@base@1h</CoverAlternateMovementClipSetHash>
<CoverWeaponClipSetHash>Cover_Wpn_Pistol</CoverWeaponClipSetHash>
<MotionClipSetHash>weapons@pistol_1h@gang</MotionClipSetHash>
<MotionFilterHash>BothArms_filter</MotionFilterHash>
<MotionCrouchClipSetHash />
<MotionStrafingClipSetHash />
<MotionStrafingStealthClipSetHash />
<MotionStrafingUpperBodyClipSetHash />
<WeaponClipSetHash>weapons@pistol_1h@gang</WeaponClipSetHash>
<WeaponClipSetStreamedHash>weapons@pistol_1h@gang_str</WeaponClipSetStreamedHash>
<WeaponClipSetHashInjured>weapons@pistol@pistol_injured</WeaponClipSetHashInjured>
<WeaponClipSetHashStealth>weapons@pistol@pistol@stealth</WeaponClipSetHashStealth>
<WeaponClipSetHashHiCover />
<AlternativeClipSetWhenBlocked />
<ScopeWeaponClipSet />
<AlternateAimingStandingClipSetHash />
<AlternateAimingCrouchingClipSetHash />
<FiringVariationsStandingClipSetHash>combat_fire_variations_gang_pistol_1H</FiringVariationsStandingClipSetHash>
<FiringVariationsCrouchingClipSetHash />
<AimTurnStandingClipSetHash>combat_aim_turns_pistol</AimTurnStandingClipSetHash>
<AimTurnCrouchingClipSetHash />
<MeleeClipSetHash>melee@pistol@streamed_core</MeleeClipSetHash>
<MeleeVariationClipSetHash />
<MeleeTauntClipSetHash />
<MeleeSupportTauntClipSetHash />
<MeleeStealthClipSetHash />
<ShellShockedClipSetHash>reaction@shellshock@unarmed</ShellShockedClipSetHash>
<JumpUpperbodyClipSetHash>MOVE_JUMP@WEAPONS@PISTOL</JumpUpperbodyClipSetHash>
<FallUpperbodyClipSetHash>MOVE_FALL@WEAPONS@PISTOL</FallUpperbodyClipSetHash>
<FromStrafeTransitionUpperBodyClipSetHash>weapons@pistol_1h@gang</FromStrafeTransitionUpperBodyClipSetHash>
<SwapWeaponFilterHash>RightArm_NoSpine_filter</SwapWeaponFilterHash>
<SwapWeaponInLowCoverFilterHash>RightArm_NoSpine_filter</SwapWeaponInLowCoverFilterHash>
<AnimFireRateModifier value="1.311718" />
<AnimBlindFireRateModifier value="1.000000" />
<AnimWantingToShootFireRateModifier value="3.000000" />
<UseFromStrafeUpperBodyAimNetwork value="true" />
<AimingDownTheBarrel value="true" />
<WeaponSwapData ref="SWAP_DEFAULT" />
<AimGrenadeThrowNormalClipsetHash />
<AimGrenadeThrowAlternateClipsetHash />
<GestureBeckonOverrideClipSetHash>combat_gestures_beckon_pistol_1h_gang</GestureBeckonOverrideClipSetHash>
<GestureOverThereOverrideClipSetHash>combat_gestures_overthere_pistol_1h_gang</GestureOverThereOverrideClipSetHash>
<GestureHaltOverrideClipSetHash>combat_gestures_halt_pistol_1h_gang</GestureHaltOverrideClipSetHash>
<GestureGlancesOverrideClipSetHash>combat_gestures_glances_pistol_1h_gang</GestureGlancesOverrideClipSetHash>
<CombatReactionOverrideClipSetHash>combat_reactions_pistol_1h_gang</CombatReactionOverrideClipSetHash>
<UseLeftHandIKAllowTags value="true" />
</Item>