First, with SparkIV, export your WEAPONS.ivaud from resident.rpf (find it in
pc\audio\Sfx). Open the WEAPONS.ivaud with GTA IV-aud and import all sound files
to here (match the names):

PUMPACTION_SHOT_L
PUMPACTION_SHOT_R

Save once done and import back to resident.rpf, Save and close.

Install one of these weapon line versions you like to Baretta line (edited a bit from the Blood Prison Guns Pack).

Buckshot version of B. Tactical

	<weapon type="BARETTA">
		<data slot="SHOTGUN" firetype="INSTANT_HIT" damagetype="BULLET" group="SHOTGUN" targetrange="10.0" weaponrange="160" clipsize="10" ammomax="80" timebetweenshots="433">
			<damage base="36" networkplayermod="5.0" networkpedmod="1.0"/>
			<physics force="18.75"/>
			<reload time="2666" fasttime="1666" crouchtime="2666"/>

			<aiming accuracy="0.02015" pellets="16">
				<offset x="0.14" y="1.0" z="0.55"/>
				<crouchedoffset x="0.15" y="1.0" z="0.05"/>
				<reticule standing="1.0" ducked="1.0" scale="0.0"/>
			</aiming>

			<pickup regentime="240000" ammoonstreet="16"/>

			<controller>
				<rumble duration="180" intensity="0.8"/>
			</controller>

			<flags>
				<flag>GUN</flag>
				<flag>CAN_AIM</flag>
				<flag>CAN_FREE_AIM</flag>
				<flag>ANIM_RELOAD</flag>
				<flag>ANIM_CROUCH_FIRE</flag>
				<flag>2HANDED</flag>
				<flag>HIGHER_BREAK_FORCE</flag>
			</flags>
		</data>

		<assets model="w_pumpshot">
			<anim group="gun@baretta">
				<rates firerate="1.3" blindfirerate="1.3"/>
			</anim>
			<effects>
				<muzzle fx="muz_shotgun"/>
				<shell fx="weap_ejected_shotgun"/>
			</effects>
		</assets>
	</weapon>

Slug version of B. Tactical

	<weapon type="BARETTA">
		<data slot="SHOTGUN" firetype="INSTANT_HIT" damagetype="BULLET" group="SHOTGUN" targetrange="10.0" weaponrange="700" clipsize="10" ammomax="80" timebetweenshots="433">
			<damage base="50" networkplayermod="5.0" networkpedmod="1.0"/>
			<physics force="30"/>
			<reload time="2666" fasttime="1666" crouchtime="2666"/>

			<aiming accuracy="5.0" pellets="1">
				<offset x="0.14" y="1.0" z="0.55"/>
				<crouchedoffset x="0.15" y="1.0" z="0.05"/>
				<reticule standing="0.1" ducked="0.1" scale="0.0"/>
			</aiming>

			<pickup regentime="240000" ammoonstreet="16"/>

			<controller>
				<rumble duration="180" intensity="0.8"/>
			</controller>

			<flags>
				<flag>GUN</flag>
				<flag>CAN_AIM</flag>
				<flag>CAN_FREE_AIM</flag>
				<flag>ANIM_RELOAD</flag>
				<flag>ANIM_CROUCH_FIRE</flag>
				<flag>2HANDED</flag>
				<flag>HIGHER_BREAK_FORCE</flag>
			</flags>
		</data>

		<assets model="w_pumpshot">
			<anim group="gun@baretta">
				<rates firerate="1.3" blindfirerate="1.3"/>
			</anim>
			<effects>
				<muzzle fx="muz_shotgun"/>
				<shell fx="weap_ejected_shotgun"/>
			</effects>
		</assets>
	</weapon>
