I'm really scared of lawyers, so I'll say I don't own My Little Pony and no copyright infringement is intended.
How do ponies use modern weapons with hooves? This is something I have pondered from perusing certain fanfics and fanart, so here is my very silly answer to this question. Enjoy! Um, if that's okay with you...
Dastardly, bastardly Griffons are invading Equestria! By mysterious and contrived means, they cross a thousand miles of open territory, bypass all defenses completely undetected, and dump a whole army group complete with armor and portable lavatories on the outskirts of Ponyville. The small town is a target of great plot significance, and it will assuredly fall to the invaders…
But not if Sergeant Dead Eye, Royal Equestrian Army has anything to say about it!
The Griffons lie down a withering hail of hot copper-coated lead, forcing the ponies in the foxhole to keep their heads down.
“Crack Shot, Meat Shield! Give covering fire! Red Shirt and I will go around that building and flank ‘em!” The two soldiers nod in affirmation. Sergeant Dead Eye counts to three…
He leaps from the hole and runs. Bullets fly. Thankfully they all miss, because they all slam into Private Red Shirt instead.
“AAAAAAAAAAAAAAAHHHHHHHHHHHHHHH!” he shrieks for an unnecessarily long time before catching a RPG with his face.
Dead Eye makes it behind the building alone and leans his back against the brick wall. “Time to make those feather brains pay!” he growls as he readies his M4 carbine. He pulls on the T-shaped cocking handle at the top rear of the receiver, and the weapon promptly flies out of his hooves and lands in the dirt.
“Dammit!” The sergeant retrieves his weapon and braces his left hoof behind the pistol grip. He fumbles with the cocking handle with his other hoof, but he can’t get a grip on the small half-inch prongs.
More bullets whiz past the brick wall Dead Eye is covering behind, reminding him that the Griffons are indeed still trying to kill him. The sergeant spews various swear words as he tries to load his first round in the chamber again and again without success. Finally, he decides to simply bite on the cocking handle and pull, and to his surprise and relief, it works. Now he’s ready to sate his bloodlust and defend his country!
Sergeant Dead Eye awkwardly cradles his M4 in his fore hooves. He steps to shoot around the corner, and immediately loses balance and falls to the ground. Standing on rear hooves is hard. Fortunately, his belly flop into a bed of flowers keeps him down and out of sight of the bullets seeking to violate him. He swears under his breath and decides to shoot while prone. He delicately balances his carbine upright on its thirty round magazine, awkwardly scrunches down his long neck to look through the optical sight, and takes aim. He places the red dot over a griffon’s chest.
“DIE!” he says as he pulls the trigger.
Nothing happens. Dead Eye’s right hoof simply slides across metal. He tries again, but he can’t fit his hoof into the trigger guard!
“DAMN YOU EUGENE STONER!” he shouts to the heavens.
The Griffons are now a stone’s throw away, but a grenade is a better idea in this perilous situation. Sergeant Dead Eye drops the M4 carbine in disgust. Which jackass’ idea was it to issue him that poorly designed gun anyway? He pulls a grenade from his flak vest with his teeth. He braces the bomb in his hooves, bites the safety pin ring, and gives it a yank.
The pin comes out, and the grenade happily falls out of Dead Eye’s grip, which with hooves is rather suboptimal. Once free of the pin and any pressure from holding it down, the safety lever pops off with a cheerful bing!
“Black Hawk down! I repeat, Black Hawk down!” announces a voice over the radio.
The poor bird of prey falls to earth in a spray of smoking meaty chunks and charred feathers. Fluttershy will give those mean griffons a stern talking-to about cruelty to animals when the battle is over. By sheer coincidence, a black UH-60 tactical transport helicopter accompanies the raptor’s dive to death and crashes into Mr. Breezy’s fan shop, resulting in a fantastic, fanciful explosion.
Wounded ground troops need evacuation. Downed helicopter crews need recovering. That’s a mission for Lieutenant Steel Rain!
The pegasus mare flies to the rescue in the best possible manner – by flying a highly expensive and complicated piece of machinery. She guides the Black Hawk helicopter with well-practiced, skillful hooves.
“Dammit!” she swears as her hooves slip and jerk the joystick yet again. The helicopter drunkenly lurches sideways. Steel Rain returns the cycle-pitch lever between her hooves’ embrace, but not without accidentally pressing the firing button for the Black Hawk’s rocket pods. Now free from their prison, the rocket miscreants fulfill their Hitlerite ambitions by interrupting the Ponyville orphanage’s Pet a Puppy Day.
Steel Rain somehow manages to keep the Black Hawk in the air long enough to approach the casualties she’s supposed to be rescuing. Unfortunately, descending requires use of the collective-pitch lever. Her fore hooves reach for those controls, forcing her to scrunch up and press her hind legs together to keep the main joystick steady, which in turn takes her rear hooves off the floor pedals controlling the tail rotor.
The Black Hawk spins in place. Lieutenant Steel Rain frantically flails at the controls to reign in her wayward helicopter, but then it starts sliding sideways and spinning.
“Can’t get any worse than this,” she breathes.
A heat-seeker screams towards her twirling, dancing helicopter, and the IR missile indicator beeps and blinks into life. Steel Rain mashes a hoof on the control panel to deploy countermeasures, but her clumsy appendage instead hits the button to jettison the external fuel tanks. The missile warning continues to beep.
“Who designed these controls?” she snaps. She finally hits the right button to deploy flares, but as her luck will have it, a second missile seeks out her helicopter.
“Buck this!” Lieutenant Steel Rain kicks the cockpit door open and jumps out of the Black Hawk. She has perfectly good wings and she intends to use them! She relishes her newfound freedom for about one second before she is struck by cold reality, which just happens to be her flailing helicopter’s tail rotor. Any pony or griffon watching learns that a pegasus can indeed blend.
“Another casualty! He looks bad!” shouts a unicorn levitating a stretcher into the overflowing medical tent.
The wounded soldier is plopped screaming on the operating table. His dog tags identify him as Private Meat Shield. “AAAAAAAAAAAAAAAAAAAAAAAAAA–!”
“SHUT UP!” Doctor Saw Bones says reassuringly. “Get me my surgeon’s kit!” he orders to a nearby aid.
It's time to operate, and there's nopony more qualified than Doctor Saw Bones! He first has to get access to the wound, which requires him to take off the soldier’s vest. But it’s easier and quicker to just cut the clothing open. Time is of the essence! The doctor takes a pair of scissors in his hooves and immediately drops them into the bloodstained grass.
“Dammit!” he curses. He retrieves them with his mouth, and finds himself in a conundrum. He can hold the scissors in his mouth and not be able to cut with the blades, or he can try moving the blades with his hooves but be unable to hold them tightly.
Saw Bones spits out the scissors and puts a knife in his mouth instead. He roughly cuts the vest open along its seam, and accidentally gives the casualty some good pokes in the process.
“Put pressure on the wound!” the doctor orders an assistant. The assistant presses her hooves on the bloody hole in the soldier’s chest.
“Not with your hooves, you idiot!” Saw Bones screams. “Your hooves have been in the DIRT!”
As the assistant struggles to come up with another solution, Doctor Saw Bones retrieves his special pliers to extract the bullet. They fall out of his hooves and onto the ground.
He swears profusely, bites the tool, and hurriedly cleans it with some antiseptic. Now it’s time to operate!
He can’t open or close the pliers with his mouth.
“GAAAAH!” Saw Bones screams in frustration and the pliers fall out. He spots the unicorn stretcher-bearer running in with another casualty and rounds on him. “YOU! Why aren’t you the surgeon?”
“Levitating wounded is a very delicate job!” the unicorn replies as he runs out again.
“–AAAAAAAAAAAAAAAAAAAAAAAAAA–!” Private Meat Shield continues to scream.
Meat Shield urgently needs care more precise than a chainsaw-delivered chest amputation, but Doctor Saw Bones can’t give him that. If he can’t save the poor bastard’s life, he mind as well put him out of his misery.
“Right! We’re doing this the old fashioned way!” he shouts. “Get me my shotgun!”
A terrified aid delivers the double-barreled break-open 8-gauge. Saw Bones cradles the weapon in his hooves and slides two shells into the breeches with his teeth. He snaps it shut and aims for a mercy kill.
“Sorry buddy.” He pulls the trigger.
Nothing happens. His hoof can’t fit inside the trigger guard.
Doctor Saw Bones’ scream of frustration is drowned out by a flaming Black Hawk helicopter crashing loudly through the medical tent and exploding.