@bananamancer
Well. Yes, I see. But complexity of the battle saddle systems and not great level of technological advance of the postapocaliptic society after the bigbadaboom just makes it not possible for the vast majority of equestrians to have those. Instead, I come up with the design for the mass production in the style of STEN, Luty or M3 with the accuracy and firepower for the given money (i.g. toob gun)
It’s very improvised, but modular design with not just simple blowback, but the delayed blowback system, that renders recoil to much more comfortable level. And it’s .380, that’s much lighter for the teethes than even the 9mm, and much less recoil then .45. Also, it has a system like what box fighters uses, with compensation of the recoil to the whole bone, and not the teethes. So, it’s improvised gun for the improvising pony, I guess. She is mostly scavanger and mercenary, with the surplus equestrian army armor from before great war, and she just want to run, shoot and live her best. I think that particular gun suits her needs.
(Sorry for my English, not the first language ^^”)

@Seiza-chan
Yeah, I know ponies in FoE are plenty durable enough to use firearms with their mouths; the idea that they would design them that way, rather than with a control harness, chest mount, and head-aimed pulley/tension wire system just bothers me. The whole “light guns in the mouth, heavy guns on battle saddles” idea works at surface level, and Kkat never really expanded on the idea in the story because there was no reason to include such details in the narrative; however, I’ve written a story in which one of the supporting characters is an experienced gunsmith responsible for most of a region’s firearms, so I wound up thinking about it a lot more than is really necessary :D

Ponies, or at least Earth Ponies and Pegasi, likely would design guns with more mechanical aids than you typically see depicted in FoE stories. Ergo, tension wires (think bicycle break wires) for pulling the trigger and aiming via moving the head with an attached bridle/harness connected to the battle saddle, and rather than the 20-30 round magazines common to terrestrial firearms, most of their guns would be designed around either belt feeding or, as technology progressed into magically-augmented mechanisms, some form of feeder system (such as the PipBuck’s inventory sorting spell, which, purportedly, physically moves things around in your bags for efficient access and storage) that would take care of ammunition alignment as it transfers from a larger hopper to the feed chute.

You wouldn’t have a rifle fixed permanently in place on your sides, as Calamity does with his sniper rifles, but instead a swiveling rack mount that would allow either gun to aim in a narrow cone, thus allowing fine adjustment with the head controls once you’re pointing roughly at the target. In a similar vein, sidearms (pistol/SMG) could be mounted on the chest (an equine’s pectoral region, between the neck and foreshoulders) and would be an ideal candidate for laser or collimator sights (WWI equivalent of the holographic dot sight).

Describing guns in terms of human design in pony stories (or artwork), rather than putting in the effort to think about things on a mechanical and ergonomic level, bothers me perhaps more than it should. I can’t help it :D

@bananamancer
It is not only mouth-held, but also automatic! :D Well, she’s not holding on with her teeth or anything, she’s holding it on with her jaw muscles, and they’re very strong. And it’s much faster to accurately point at an enemy - you don’t have to move your whole body towards the bad guy. You see it - you shoot it, and it correlates with her fighting style, fast and quite dangerous.

Ew, mouth-held guns. Someone get that pony a proper battle saddle :D