This story shows great potential no grammatical errors I could see I'm wondering if it's tied to the walking dead universe

I've never shot a real gun before.

This gun isn't going to last too long in the hands of an owner who's never owned a gun before.
(That's why they give you owners manuals with them. Just like a car, you have to know how to maintain it in order to get the thing to last more than a few years.)
In his hands, even if he gets an infinite supply of ammo, he's gonna demolish that thing within a decade.
Granted, that's plenty of time for the immediate premise of the story, I'm just saying, it won't last him a life time in Equestria (and I doubt the ponies know enough about the finer workings of a firearm and what they need in terms of proper oils for lubrication, proper cleaning methods, etc.).

As well, if he's never even fired one, he's got NO ingrained safety habits.
Life and limb saving things like trigger discipline, knowing not to get your fingers too close to the cylinder gap of a revolver unless you don't care about explosive amputation of your digits, and knowing NEVER to empty a misfired round into ones hand (my uncle had to have his index finger surgically re-attached after this EXACT incident occurred while unloading a misfired .22 LR from a revolver. And that's just what a dinky little .22 round will do!)

There are MANY more things to learn with firearms, and each kind of weapon requires ~virtually~ an entire new set of know-how.

6673624 here, I will keep track of how long till one of said things happen, because I am sadistic like that

Holy Throne! You've grabbed my attention!

Okey... its cool