The SIG MCX-SPEAR has made its way toCall of Duty: Modern Warfare 3as the BAS-B, a hard-hitting battle rifle that can down an opponent in as little as three bullets. Paired with its fast fire rate, it’s easy to see why the BAS-B has become a meta contender within the pre-season for MW3.

But as with all weapons in CoD, the BAS-B can become far stronger with the right use of Gunsmith attachments. This guide will cover some of the strongest builds you can use for the BAS-B, showcasing an excellent accuracy build, aggressive stealth variant, and more.

Updated June 26, 2025, by Charles Burgar:The BAS-B has seen some balance changes and a new conversion kit since we originally wrote this article. To help you create the ultimate BAS-B loadout, we’ve updated this list to include up-to-date attachment and loadout recommendations for our accuracy and stealth builds. Additionally, we’ve also created a new build that uses the JAK Outlaw Kit, converting the BAS-B into a lever-action rifle.

Pros And Cons

While the BAS-B has some serious firepower, each round invokes some serious recoil that makes long-range gunfights a gamble. Thankfully, it’s fairly easy to improve the accuracy of this weapon to make it theultimate mid-range dueling AR. We spec heavily intohorizontal recoilandfiring aim stabilityto keep the weapon’s recoil as predictable as possible.

Most of the weapon’s horizontal recoil can be removed by equipping theCasus Brake Lmuzzle and theBruen Heavy Support Grip.Both attachments also give you firing aim stability, making each shot land closer together. Throw on theSTT88 Grip,and your rounds will practically overlap one another. We finish the build by installing theBruen Venom Long Barrel, increasing the weapon’s effective range with minimal downsides.

Field Upgrade

Trophy System or Dead Silence

Since the BAS-B is a fairly slow weapon, a more passive loadout is ideal for reaching this gun’s potential. TheGunner Vestis perfect here, spawning you with additional ammunition and permanent Sleight of Hand. Boots can’t be equipped with this vest, but that can be circumvented with Field Upgrades or a playstyle shift. Use theMarksman Glovesto reduce incoming flinch, and equipEODto survive enemy explosives.

As for equipment, the Gunner Vest allows you to equip anyprimary weapon in your secondary slot. We recommend a weapon with a low TTK at close range, ideallyan SMG or shotgun.For throwable equipment, useStimsto heal yourself andBreacher Dronesto kill distant targets. Finally, your Field Upgrade should cater to your playstyle or game mode. TheTrophy Systemis great for objective modes and more passive playstyles, whileDead Silenceis better for more aggressive players.

The BAS-B is a fairly slow battle rifle that rewards precision, but you can turn this weapon into a more aggressive primary with the right attachments. TheCrippling Malice Light Barrelhas an inbuilt suppressor that will hide your minimap pings when firing the BAS-B, and it also greatly improves your strafe speed.

The same is true for theDR-6 Handstopunderbarrel grip, both of which stack to make your strafe speed comparable to most AR builds. Your recoil will suffer at medium ranges with both attachments, so we recommend using theBruen Minteuman Stockto add some much-needed aim stability and recoil control to the build.

For the last two attachments, we recommend the30 Round Magfor some added leeway in gunfights andany opticto replace the BAS-B’s iron sights. This weapon won’t win any awards for aggressive players, but you will have faster strafe speeds, suppressed shots, and controllable recoil.Pre-aim around corners when you can, and lean into the gun’s strafe speed to win duels.

Stim or Battle Rage

Preference

Suppressed weapons require a stealth build to become truly effective. We recommend theEngineer Vestfor this loadout since it comes with an extra gear slot and greatly reduces your Field Upgrade cooldown.Covert Sneakerswill muffle your footstep audio for everyone, making it easier to flank targets or hear enemy players.Ghostshould also be used to hide yourself from UAVs and other sensor equipment.

To help with the BAS-B’s long reload time, use the Mag Holstergear perk. And for those mid-range duels where every shot counts, use the Marksman Glovesto make yourself much more resistant to flinch.

The equipment for this build is mostly down to preference and will vary based on the active game type. For secondaries,any close-range weaponswill work. The Renetti converted into a carbine,shotgun revolvers, and melee weapons are good choices. Field Upgrades don’t matter for this build; use what you like.

For your Tactical, we recommendStims or Battle Rage.You should use Battle Rage before a fight to gain infinite tactical sprint, resistance to tactical equipment, and a heal-on-kill property that’s similar to MW2’s Quick Fix perk. Stims offer less utility but can be used after gunfights to great effect. Pick whichever equipment better suits your playstyle.

The JAK Outlaw-277 Kit converts the BAS-B into alever-action rifle, giving it a damage profile that’s similar to the Longbow and other sniper rifles. The main drawback is the decreased fire rate, but that hardly matters when you can one-tap an opponent with a single torso shot. To make this playstyle even stronger, we go all-in onhandlingstats andmobilityto create a powerful one-hit kill weapon.

After you install the Outlaw Kit, you’ll be able to equip theSawed Off Stockto greatly improve the BAS-B’s ADS speed, completely mitigating the conversion kit’s handling penalties. We then use theXRX Edge BW-4 HandstopandLight 9'' Brune Wyvern Barrelto improve the weapon’s ADS speed and handling stats. Finish the build withyour choice of suppressor.We recommend the Sonic Suppressor L for a range boost.

Since this build uses a silenced weapon, we recommend the same loadout configuration as our stealth build. TheEngineer Vestgives you tons of perks to play with and double the Tactical uses per life.GhostandCovert Sneakersare perfect for stealth play, andMag Holsterfixes the slow reload speed of the BAS-B. RunStimsto heal yourself, and you’ll dominate just about every Multiplayer lobby.