From Brotato Wiki
SMG is a weapon that can be bought from Shop. Weapons are primary damage dealers and most Characters can hold up to 6 weapons.
SMG is a Ranged Weapon. Ranged weapon shoots a projectile what travels up to total Range. If the weapon has no pierce, the projectile only damages only one enemy.
The SMG is a fast shooting gun with good single target damage output. This makes it great at quickly reacting to enemies that charge or spawn next to you.
The SMG has a low base damage, but a high scaling with Ranged Damage. Neither the Base damage nor Attack Speed of the SMG increase significantly as you upgrade the gun to higher tiers, but its scaling with Range damage Increases with each tier. So a good amount of Ranged Damage is important.
The SMG's shots are quite inaccurate and might miss their target at longer range.
Due to the fast firing speed, SMG's can trigger Life Steal very often, making it a powerful option for your healing.
The SMG can struggle with clearing large groups of enemies. You can solve this issue by getting items such as Bandana, Baby with a Beard, or Ricochet. Or you can pick up another gun with better damage against big groups of enemies like Double Barrel Shotgun or Shredder.
The SMG has a critical hit multiplier of 1.5x instead of the regular 2x. This means Crit Chance only has half of the increase on your damage output compared to most other weapons. Take this into account when investing into the stat.
Weapons in the same class gain bonuses, and are more likely to be found in the Shop.