First, edit your animgrp.dat. Use Find option (Ctrl + F) and find "Weapon groups".
Below is the list of streaming weapon animations. Replace it with this from up to
down:

WeaponGroup( Streaming, gun@ak47 )
WeaponGroup( Streaming, gun@baretta )
WeaponGroup( Streaming, gun@deagle )
WeaponGroup( Streaming, gun@handgun )
WeaponGroup( Streaming, gun@m249 )
WeaponGroup( Streaming, gun@mp5k )
WeaponGroup( Streaming, gun@rocket )
WeaponGroup( Streaming, gun@shotgun )
WeaponGroup( Streaming, gun@uzi )

Save and close.

Second, edit your default.ide. This file plays vital role on your GTA IV.
Scroll to w_ak47 and replace it with this:

w_ak47, 		w_ak47, 		gun@m249, 		1, 	50, 	0

Save and close.

After that, 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):

AK47_SHOT2_A_L
AK47_SHOT2_B_L
AK47_SHOT2_C_L
AK47_SHOT2_D_L
AK47_SHOT2_E_L
AK47_SHOT1_L
AK47_SHOT1_R

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

Finally, install the new WeaponInfo to AK47 line below.

	<weapon type="AK47">
		<data slot="RIFLE" firetype="INSTANT_HIT" damagetype="BULLET" group="RIFLE_ASSAULT" targetrange="5.0" weaponrange="1259.5" clipsize="200" ammomax="600" timebetweenshots="66">
			<damage base="30" networkplayermod="2.0" networkpedmod="1.0"/>
			<physics force="75.0"/>
			<reload time="2066" fasttime="1166" crouchtime="2066"/>

			<aiming accuracy="0.75">
				<offset         x="0.16" y="1.0" z="0.55"/>
				<crouchedoffset x="0.1"  y="1.0" z="0.12"/>
				<reticule standing="0.6" ducked="0.5" scale="0.3"/>
			</aiming>

			<pickup regentime="480000" ammoonstreet="80"/>

			<controller>
				<rumble duration="90" intensity="0.1"/>
			</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>
			</flags>
		</data>

		<assets model="w_ak47">
			<anim group="gun@m249">
				<rates firerate="1" blindfirerate="1.99"/>
			</anim>

			<effects>
				<muzzle fx="muz_machine"/>
				<shell fx="weap_ejected_rifle"/>
			</effects>
		</assets>
	</weapon>