	<weapon type="SNIPERRIFLE">
		<data slot="SNIPER" firetype="PROJECTILE" damagetype="FIRE" group="RIFLE_SNIPER" targetrange="50.0" weaponrange="1500.0" clipsize="10" ammomax="70" timebetweenshots="400">
			<damage base="400" fps="75" networkplayermod="2.0" networkpedmod="1.0"/>
			<physics force="125.0"/>
			<reload time="2066" fasttime="2066" crouchtime="2066"/>

			<aiming accuracy="10.0" accuracyfps="0.0">
				<offset x="0.16" y="1.0" z="0.55"/>
				<crouchedoffset x="0.16" y="1.0" z="0.12"/>
				<reticule standing="0.6" ducked="0.5" scale="0.05"/>
			</aiming>

			<pickup regentime="360000" ammoonstreet="10"/>

			<controller>
				<rumble duration="120" intensity="0.3"/>
			</controller>

			<flags>
				<flag>GUN</flag>
				<flag>2HANDED</flag>
				<flag>ANIM_RELOAD</flag>
				<flag>CAN_FREE_AIM</flag>
				<flag>FIRST_PERSON</flag>
				<flag>ANIM_CROUCH_FIRE</flag>
			</flags>

			<projectile type="IMPACT">
				<explosion type="MOLOTOV"/>
				<physics force="33.0" vehiclevelocity="8.0"/>
			</projectile>
		</data>

		<assets model="w_psg1">
			<anim group="gun@rifle"/>
		</assets>
	</weapon>

You will need the Barrett M82A1 mod or M95 mod from gta4-mods.com.
Search the name "barrett" in Search Mods box to find what you will need.
Ensure that you replace this to PSG-1, if not, switch the Weapon Type to M40a1
and Assets Model to w_rifle.