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Gunsmith Katsumi - Akitsukuni Arms Design Quest

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Character Sheet
  • Informational
    • Tachibana Katsumi

    Stress: 5/10

    Accomplishments
    Mechanical Engineering degree
    Got a job in your field
    Type 37 Special Purpose Rifle
    Type 38 Self-Loading Pistol

    Friends
    Maeda Rumi: Your roommate.
    Sanders Clara Rose: A colleague who works for Naylor, Sons & Daughters.

    Coworkers
    Mr. Watanabe: Your superior.
    Mr. Akutagawa: The boss of the company.

    Workshop 3
    Ms. Ikeda Nioh: Chemist. She also seems to be Mr Watanabe's personal secretary, but you're not sure if that's an official position.
    Mr. Yakade Yasuo: Physicist, specialized in ballistics. A living, breathing Technical Appendix C.
    Mx. Kusonoki Mayumi: Has a degree in materials science. Gets a look on their face when they say they know more about wood than anyone.
    Mr. Shiragiku Hideyoshi: Metalworker. Having met him, you've learned why metalworking is a craft and the meaning of the phrase "thinks himself heaven's gift to women".
    Mr. Kashiwa Ichiro: An apprentice gunsmith with a background in carpentry and actually using guns on people.

    Technologies
    Rifles (Familiar)
    Shotguns (Familiar)
    Pistols (Familiar)

    Rotate-and-pull bolts (Practical)
    Straight-pull bolts (Practical)
    Aperture sights (Practical)
    Stripper clips (Practical)
    Lever-delayed blowback operation (Practical)
    Double-stack magazines (Practical)
    Single-action handguns (Practical)
    En bloc clips (Conceptual)
    Simple blowback operation (Conceptual)
    Short recoil operation (Conceptual)
    Toggle-delayed blowback operation (Conceptual)
    Blow forward operation (Conceptual)
    Simple blowback operation (Conceptual)
    Double-action pistols (Conceptual)
    Automatic revolvers (Conceptual)
     
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  • Informational
    • firestorm440 said:
    May I recommend the Youtuber Drachinifel if you're interested in general naval matters up to the end of WW2?
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    Wow, okay, I remember having seen a Drachinifel video months (years?) ago but never found it again. Thanks!

    Also, holy crap, apparently the armor piercing high explosive shell was a major topic of R&D circa 1910, like, the british royal navy deploying new shells every couple years and changing its mind about how best to fire them on a monthly timescale.
    xthetenth said:
    Yep, that's where I nicked the idea from. Never confuse me being knowledgeable for being smart or innovative. :p I'm just talking about a very simple, compact 2d cam for the rear sight lateral windage as a sort of BDC for windage.

    If you want an outstanding video going through most of the simple mechanisms for a mechanical computing system, the USN put one together.
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    Hah, same video I was working off of. :p I love those US training videos.
     
    Vebyast said:
    Also, holy crap, apparently the armor piercing high explosive shell was a major topic of R&D circa 1910, like, the british royal navy deploying new shells every couple years and changing its mind about how best to fire them on a monthly timescale.
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    The rate of naval R&D from late Victorian to the beginning of the Cold War was genuinely absurd. In 40 years the apex of naval development went from HMS Dreadnought to the Midway-class aircraft carriers and the Type XXI Elektroboot.
     
    firestorm440 said:
    The rate of naval R&D from late Victorian to the beginning of the Cold War was genuinely absurd. In 40 years the apex of naval development went from HMS Dreadnought to the Midway-class aircraft carriers and the Type XXI Elektroboot.
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    And we're now further from the Falklands war than that war was to WW2, and the mainline combatants of the USN are developments of designs work on which first started before that conflict.
     
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    The list of factions in Akitsukuni society that want something like that and the list of ones I want to be making arms specifically for have nothing at all in common.
     
    Sir_Travelsalot said:
    I can't think of a reason why armed security would want silencers on their weapons. If they have cause to be firing them, making as much noise as possible would be a good thing, surely?
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    Except for the part where it blows out the Empress's eardrums. Suppressed weapons are still pretty loud, the empress should be under constant observation anyway, and if they need more noise they can blow a whistle or something.

    edit: I think the real advantage would be that the imperial guard are likely to be engaging in close quarters and at those ranges an SMG with a 30-round detachable stick magazine would be a major firepower upgrade over a bolt-action rifle with a six-round magazine loaded via stripper clips. Same kinds of reason you see modern anti-terror units using them.
     
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    Wait Suppressors have a proper use in Hunting and arent really that silent anyways its more of not wanting to become deaf measure during the early period so a suppressor on this gun may actually be a boon
     
    Helher said:
    Wait Suppressors have a proper use in Hunting and arent really that silent anyways its more of not wanting to become deaf measure during the early period so a suppressor on this gun may actually be a boon
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    In general terms, yes, but the De Lisle carbine belongs with the Welrod, MP5SD and AS VAL in that class of specially designed integrally suppressed weapons which are as good as silent. As a result of the compromises needed to achieve this it's not really suitable as a highly accurate weapon, which is what Tachibana decided to do.

    In terms of putting a suppressor on this gun, I'm not particularly up on my principles of operation but I think smashing gas through one at over 900 m/s will probably wreck it annoyingly quickly.
     
    FrangibleCover said:
    In general terms, yes, but the De Lisle carbine belongs with the Welrod, MP5SD and AS VAL in that class of specially designed integrally suppressed weapons which are as good as silent. As a result of the compromises needed to achieve this it's not really suitable as a highly accurate weapon, which is what Tachibana decided to do.

    In terms of putting a suppressor on this gun, I'm not particularly up on my principles of operation but I think smashing gas through one at over 900 m/s will probably wreck it annoyingly quickly.
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    It really depends on how you build the suppressor and such.

    The welrod is part of the family of suppressors where you shoot through initially solid rubber intended to trap in gasses and thus inevitably degrade the suppressor as you shoot more holes in them.
    Meanwhile, the AS Val and its daddy rifle the VSS Vintorez instead go the route of having most of the barrel be a really long suppressor that gradually diverts, depressurizes, and slows gas as the bullet travels, something where if you build the suppressor for the strain it will be expected to withstand it'll last quite long indeed.

    Actually, there's some weirdness to do with that sort of thing: if you use the gas diversion type of suppressor and your cartridge, as often happens, would generally fail to fully burn the powder while the bullet is in the barrel (and thus normally waste energy without accelerating the round), you'll actually usually get an increase in muzzle velocity because you extended the 'powerstroke' received by the bullet, even if it's less so than a normal barrel extension would grant. Could result in the embarrassing outcome of designing a barely subsonic round but fucking up to the degree that if you use a suppressor it becomes a supersonic one.
     
    We could also look at building one of these, which has a sabot that gets wedged at the end of the barrel and seals it to contain the propellant gases. I can't figure out how it handles multiple shots, but I suspect that it cycles slowly to give the propellant gases time to vent and the very last operation in the cycle involves knocking the sabot out of the choke at the muzzle. Apparently these are totally silent - the sources I can find say the only discernible noise is a "click" from the firing pin falling off the sear and maybe some noise from the slide hitting various buffers at low speed.
     
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    Quick overview of the anatomy of a gunshot:

    All the loud noises are just what happens when shockwaves propagate into the air. Guns generally have three major sources, the mechanical stuff moving around, which in the scheme of things is pretty quiet, the bullet if it's supersonic is producing a sonic boom, a continual noise source across the flight of the bullet, and lastly the gunpowder is an explosion with all the resulting shockwave in air business at the leading edge of it. That's a quite loud single source sound and a huge contributor to the sense of where a gunshot is coming from.

    Welrods and De Lisles take on all of those sources by not having the gun cycle an action, a suppressor to absorb the shot (and not just using a tight fit, having the bullet hole out rubber grommets so there's a decent period where there's a no-kidding seal ensuring no gas gets ahead of the bullet, so an effective if short lived suppressor), and then having a subsonic bullet that doesn't produce any sonic boom. It's really quiet. For the same reason that it's nearly silent, it's not a great weapon to get in a fight with, rather you want to be undetected and remain that way.

    The AS Val and its ilk (a pretty expanded category when you get down to it, because it includes things like literally every subgun in .45 ACP if you put a can on the end) have an action, but are otherwise quite quiet. You can get more or less effect depending on the design of the suppressor and how much volume it has to absorb the explosion, with the upper end of the effect being basically the loudish rattle of the gun racking itself repeatedly. This can be very quiet without being incredibly limited in a fight against an alerted opponent.

    Then there's other guns with a suppressor. There might be a pretty big amount of shockwave left over to escape out of the can, especially with small suppressors on short barrels, which can be intended to just drop the noise enough to not permanently damage hearing, and there's a sonic boom from the bullet. One of the main things from these setups is that the overall noise level is lower, probably hearing safe, and a lot less of it is coming from a single location right next to the shooter. People will probably know there's a shooter but it makes it a lot harder to pinpoint where the shooter is. Basically anything can be this.

    Also, suppressors' biggest design opponents are heat, erosion, simplicity, and the US NFA. Heat saturation destroys cans. The ones that hold up to heavy wear are built solid and use the fruits of modern materials science liberally, and they basically universally suck to machine. Stuff like stellite, titanium and inconel show up, especially in the US civilian market where you can't just ditch a suppressor or swap out parts of it trivially. But basically it's absorbing a ton of heat through relatively thin material and getting abraded while very hot. If you want it to not be a wear component, that's a really tricky engineering challenge. If you're willing to add complexity and make it multi-part, whatever, you can replace the internals pretty easily. If you don't need light weight and fast fire and can replace internals, it's not that hard. If you do, it can be seriously expensive.
     
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    Vebyast said:
    We could also look at building one of these, which has a sabot that gets wedged at the end of the barrel and seals it to contain the propellant gases. I can't figure out how it handles multiple shots, but I suspect that it cycles slowly to give the propellant gases time to vent and the very last operation in the cycle involves knocking the sabot out of the choke at the muzzle. Apparently these are totally silent - the sources I can find say the only discernible noise is a "click" from the firing pin falling off the sear and maybe some noise from the slide hitting various buffers at low speed.
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    Actually, how the PSS family works is that the cartridges contain tiny gas pistons that physically push the bullet fast enough to launch it after powder combustion happens, but don't leave the cartridges and form a gas seal at the cartridge mouth. The cases are then ejected still full of, but slowly leaking, the propellant gasses.

    It's a technique the Russians have also used in a revolver and a knife.
     
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    plotvitalnpc said:
    but don't leave the cartridges and form a gas seal at the cartridge mouth
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    ...Huh. Okay. I feel like I'd still call that a "sabot", but I hadn't caught that it stops at the end of the cartridge rather than at the end of the barrel. Interesting.

    edit: Now I'm wondering what my definition of "sabot" actually is against, I dunno, a "captive piston". Attached to the gun instead of the cartridge? Disposable?
    xthetenth said:
    The ones that hold up to heavy wear are built solid and use the fruits of modern materials science liberally, and they basically universally suck to machine.
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    I remember a youtube video a while back about a suppressor that tried to turn gas pressure into kinetic energy by pushing it through a bunch of little turbines and making it spin them up on the way out. I don't recall if it actually worked, but it made the silliest noise and looked like a machinist's worst nightmare.
     
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    Vebyast said:
    ...Huh. Okay. I feel like I'd still call that a "sabot", but I hadn't caught that it stops at the end of the cartridge rather than at the end of the barrel. Interesting.

    edit: Now I'm wondering what my definition of "sabot" actually is against, I dunno, a "captive piston". Attached to the gun instead of the cartridge? Disposable?
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    If you look at an image of the cartridge, you can see that A) the thing is way too long for the amount of powder in it if it were a conventional cartridge, and B) that it's a necked cartridge for the purpose of stopping the gas piston that kicks the bullet out from leaving the cartridge mouth and ensuring that it forms a gas seal instead.

    The result is that the thing has a maximum firing range of 50 meters because they had to lowball the power so much to fit the mechanism into even the unreasonably long pistol cartridge they created, resulting in an exceptionally light subsonic round that lacks the inertia to fly out to any reasonable distance.
    The successor pistol uses a one milimeter longer cartridge and fires chisel head shaped bullets because it was the only way they could reasonably improve the terminal ballistics without compromising on the silencing mechanism.

    It's clever if you need a pistol that's exclusively for ultra-silent assassinations, but there's no other purpose the mechanism is suitable for.

    Edit: also a sabot is a disposable wrapper on the actual projectile intended to make sure a small round can still seal the barrel and engage the rifling/stay in the center despite not being big enough.
     
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    The results are in for the most important vote of 2020! I know it was close and we were all really worried for a mome--this joke doesn't really work, you know? The winner was clear from the beginning:

    [x] Copy a front-locking design
    -[x] A rotating bolt Katzen rifle

    ActionFlawless Design!Some flawsMany flawsDelaysDisaster Strikes!
    Katzen3-67-1415-1718

    Can someone please pick one and roll:
    a) 3d6
    b) 4d6 drop highest, +1 Stress
     
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