Using a format lifted from Ikari Warriors three years ago, the game plays out like all run-and-gun games populating arcades at the time; you're a One-Man Army war hero with More Dakka and Bottomless Magazines, and you can collect assorted power-ups to facilitate your elimination of a literal army of faceless goons.
Set in what appears to be the The Vietnam War, the player(s), an American military chopper pilot, have their vehicle shot down and crashing in the South-East Asian jungles, right in the heart of enemy territory. Surviving the subsequent crash, realizing entire platoons of soldiers from the opposing side are coming for them, the player then grabs their downed vehicle's 50-Caliber automatic machine-gun and start shooting everything in sight.
Caliber .50 contain examples of:
- Airborne Mook: Every now and then, enemy forces will send aircrafts swooping into the area to take potshots on you, which can be shot out of the sky if you have enough firepower.
- Bottomless Magazines: Both your default 50. Cal and the obtainable pickups never runs dry on ammo.
- Gunship Rescue: The final level have you infiltrating the enemy airbase, and radio for another chopper for help. In the stage's last area, a US Army chopper will arrive and provide cover fire as you try forcing your way past enemies, but you'll need to kill enough mooks to allow the chopper to safely land. The game ends once you got onboard.
- Construction Vehicle Rampage: The boss of the village stage is a weaponized thresher vehicle which attacks you as you're trying to cross a farm, constantly trying to use it's front in an attempt to grind you up. While said thresher doesn't have ranged attacks, it's surprisingly fast and getting hit directly costs you an entire life.
- Crate Expectations: Shooting crates will reveal bullets, grenades, extra lives, and assorted goodies.
- Excuse Plot: You're trapped in enemy territory, and must shoot your way out.
- Fire-Breathing Weapon: You can obtain a flamethrower early on, and it averts Video Game Flamethrowers Suck by dealing insane amounts of damage to everything on the wrong side of the screen, turning entire mook platoons into piles of burning flesh before dissapearing from the screen entirely.
- Jungle Warfare: The setting of the entire game is in a thick jungle swarming with enemy soldiers. You're shot down in the heart of their base and must clean the woods of mooks.
- Maniac Monkeys: One of the Triple Bosses you have to fight is a trio of gigantic simians in an underground cavern, who attacks by flinging rock and dirt.
- Man on Fire: Thanks to your flamethrower, which makes enemy mooks burn up before disintegrating. The enemy ranks also have occasional flamethrower operators who explodes in flames when killed by any weapon.
- More Dakka: Well, given the game's title... and you can get even more powerful guns as the game progressed on, to kill more enemies.
- Named by the Adaptation: In the Sega Genesis port, at least, the unnamed player character is now given the name Captain Addis.
- Off-into-the-Distance Ending: The game ends with you boarding an army chopper, which then flies off into the sun. Roll credits.
- One-Man Army: You against an enemy army of dozens, that you spend every second of the game slaughtering.
- Pit Trap: Containing Spikes of Doom. These have a tendency to show up in empty plains, which you'll have to navigate your way around while being shot at by mooks, and falling in one leads to losing a life instantly.
- Tanks for Nothing: Tanks are occasional enemies that shows up, flanking low-level enemy soldiers, and besides being ridiculously slow, they also blow up in just a scant handful of hits from your firearms.
- Trapped Behind Enemy Lines: You at the start of the game, when your chopper gets shot down in the middle of hostile territory. The final stage have you reaching an enemy airbase and using their radio to call in a chopper for evacuation.
- Video Game Cruelty Potential: The wildlife in the game doesn't pose any threat to you, but you're free to slaughter water buffaloes (in the forest) or wild boars (in the village) for fun and gain extra points in the process. The river stage also have tortoises sticking out of the water, which flips over when you shoot at them, but they can't be killed.
- Weapon Title: The title refers to your helicopter's 50. Caliber machine-gun mounted to it's side, which you remove after crashing in enemy territory and use to kick ass on foot.
- Zerg Rush: The preferred strategy of the enemy infantry is to swarm the screen with as many onscreen mooks as possible, in order to overwhelm you through numbersd. It doesn't work thanks to you having More Dakka.