I've taken the liberty of breaking this up into distinct points regarding the rifle.
1) The 'Vin' is an automatic rifle chambered in 11mm Riviere, designed to also fit in the light machine gun role.
2) It uses a design based on a modified Wiel.b action, with a flywheel (in a slim cylindrical stamped metal housing on the top of the barrel, directly in front of the end of the receiver) that is driven by a short-stroke gas piston - like a locomotive's wheels. There is also a small gas port to let out excess gases after the action has been cycled. Due to this, it retains the Wiel's ramping fire and lack of recoil. The top of the wheel-housing is held by a snaplock, so it can be easily removed in the field.
3) It feeds from the left, out of 20-round box magazines or 60-round casket magazines, and ejects out the right. Because the Vin chambres a rimmed cartridge, the magazines have a slight but noticeable curve. Each Vin also ships with a loading guide to make it easier to reload the magazines with stripper clips.
4) Perhaps the most significant improvement over the Wiel, however, is the ready-spring: whenever the trigger is pulled, the spring will release and give the wheel a starting boost. The act of firing the first round also readies the spring, so there is no downtime required to make the gun usable. After this, the spring stays under tension until the next trigger pull. The spring is designed to be easily replaced in case of failure. If the automatic retentioning of the spring fails, there is also a tab sticking out of the wheel-housing that can be manually pulled to ready the spring. If the wheel is already going fast, the ready-spring will not boost the speed and instead slip harmlessly.
5) The Vin is select-fire with a progressive double-stage trigger: semi-automatic fire resulting from a light pull, and fully-automatic fire from a harder pull. The trigger has a spring that provides resistance when pulling the trigger past the semi-automatic position, making it harder to go into fully-automatic accidentally.
6) There is also a simple manual safety, which physically prevents the trigger from moving and locks the firing pin in place.
7) The furniture of the Vin is wood from the shoulder stock all the way to around 1/3 of the barrel's length, to allow comfortable gripping.
To help with cooling, the barrel is stepped.
9) It features both a pistol grip and a full stock as well as a carrying sling, and a folding bipod at the end of the barrel.
10) The iron sights of the weapon, a post and diopter, are raised so as to not be blocked by the wheel-housing.
11) Wherever possible without reducing quality, cast and milled metal parts have been replaced with stamped metal to aid cost.
1) For an automatic rifle (or even an lmg) 11mm is huge. I understand the appeal of using our existing round, but we really just gotta design a new one. 9mm is still pretty damn big - most lmg's used close to 7.62mm's in ww1. Even modern lmg's tend to go between 5.56 - 7.62 mm. Since this is also designed to operate both an lmg and a rifle, we need to go smaller...and even so, this will be a damn heavy gun.
2) Okay, leaning into the flywheel. At least it's using a gas piston now, so we're closer to sanity. I'd shy away from saying "lack of recoil" - the 2.b had "reduced recoil" because the recoil in the 2.a was the massive flywheel jerking in every direction. Since this flywheel is now horizontal, if it's an appreciable size the user is going to notice his aim slipping to the side while firing. But we can't really avoid these problems if we use a flywheel, so it's not a thing we can address in this design anyways.
3) 20 round box magazine OR a casket magazine? Is it belt-fed or magazine fed? It can't be both. Belt-fed means extra machinery to extract and chamber the rounds, meaning a necessarily larger gun - magazine-fed means a smaller gun, but smaller ammo supply. If I had to choose I'd go with boxmag to reduce cost of the magazine, but then you're left with a trailing ribbon of cotton as you fire. Still, I'd prefer that to a bar of metal jutting out of the side of the gun. The casket magazine may be asking for too much with all the other bells and whistles, and will definitely increase cost - it's practically a revision all on its own. Also, 20 rounds ain't much for a box mag.
4) Ready-spring is a good idea for the flywheel. Especially the self-setting and replaceability of it.
5) I'm not sure about this one. I honestly don't know a lot about double-state triggers, but it seems like the sort of thing that bumps complexity for a small amount of value. I'd leave it as a solely full-auto weapon, but if we want select fire why not use a switch?
6) This is fine.
7) I'd personally prefer more wood, but this is fine.
What do you mean by "stepped"? Since our metallurgy is inferior to prykanbuls, I'd prefer to do a cooling shroud over the barrel to help combat heat - like the lewis gun. We're going to experience barrel warping - especially since this is a "light machine gun" firing comparatively large-caliber rounds through a low-quality metal barrel.
9) This is fine.
10) This is fine. It's an lmg using a flywheel, so it's not going to be accurate anyways.
11) With all the bells and whistles we have on this gun, this part is kind of insulting. At no point is this gun cutting corners for cost, so saying "we use cheap parts where we can" doesn't
mean anything. Either leave it out, or actually design a cheap gun. Either way this is going to be expensive, probably more than the 2.b was.
Final thoughts: The Vin is an Assault Rifle disguised as an LMG. We're not going to fool anyone. It's WW1, so unless Sensei is generous I'm unsure just how much call we'll have for this type of weapon. Nations tended to prefer heavy MG emplacements and precise, accurate rifles. The calls we've been getting for rapid-fire weapons have all called for SMG type weapons - light, and equipped for trench work or easy transport. The Vin will be expensive, and could easily end up as too heavy for squad use, yet too light for emplacements. It feels like an uneasy middleground between these two extremes. I'd say either redesign it to be cheap and light, or reliable and heavy.
I'd rather do a heavy gun, personally. Design a 13x100 mm round and lean into our MG role. We currently have the strongest hold on that type of weapon, and I'd like to discourage the other teams from trying. I'm also a fan of our reputation as being able to mass-produce cheap crap, and I'd like to design purposefully cheap (but reasonably reliable) firearms, but I know I'm in the minority with that sentiment.