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Ergonomical Opinionings Requesterated

Discussion in 'Rifle Country' started by barnbwt, Apr 29, 2014.

  1. barnbwt

    barnbwt Well-Known Member

    So I'm working on a design for a rifle intended for the purpose of introducing new shooters to semi-auto center-fire. I have a number of features devised to make things easier and more intuitive for them, which I'll list below in case you'd like to suggest/add things. (Please refrain from turning it into an AR ;) ) I've figured out how I'd like to do nearly all of these, with the exception of a grip safety that also automatically switches the ejection direction for left or right handed shooters.

    My current design, The Skorparev, has either two ejectors or two extractor claws (haven't decided which should be switchable to best direct the ejection path) of which one will be deactivated depending upon which side the ambi- grip safety is depressed. The only trouble is it's hard to decide the best place to put such a device so that it is reliably engaged, on one side only, and isn't obnoxious. Presently, my thinking is to put a lever/button under very low return spring tension either;
    -Just behind the trigger lever on each side, where the base of the shooter's finger would depress it to wrap around the trigger
    -Or even further back where the shooter's index knuckle would press against the stock when they grip it
    -As a thumb rest on either side of receiver tail

    They each have pros and cons, of course, which is why I seek ya'lls' opinions. The first solution makes the trigger feel weirder, sort of like a Glock lever but on a rifle. The second is much more exposed to inadvertent activation if the manual safety is left disengaged, and may be sensitive to different hand shapes. The third is thumb activated, so more likely to be missed by shooters with a different grip or hand shape, but can probably require more force for activation without being annoying. The compact, light rifle would also be great for carry, so making it sling-safe (with manual safety) is a priority, and scabbard-safe with the manual safety off (but grip safety deactivated until needed) preferable.

    I've got material on hand for the receiver and will be cutting metal very soon, so I need to get this last detail sorted out! :)

    -All controls and functions completely/automatically ambidextrous
    -Good quality two stage trigger
    -M1 carbine adjustable iron sights
    -Manual and grip safety (manual safety locks grip safety)
    -Manual safety protrudes into thumb palm of strong hand when engaged
    -Grip safety deactivated by strong hand
    -Left/right ejection switchable based on shooter's grip (left or right)
    -Non-reciprocating charging handle built into foregrip
    -Large mag release thumb-paddles on both sides, set flush with sides
    -Last round bolt hold open, manual cock bolt hold open (see next)
    -Forearm automatically releases a locked-back bolt when re-gripped
    -Fast, low recoiling cartridge for unintimidating, flat shooting practice (7.62x25 for now)
    -Small, lightweight construction/profile suitable for young/grown shooters of all sizes
    -Uses PPSH mags/drums of all capacities
    -Straight, wooden stock to alleviate any 'military' aversion by anti's/new shooters* (until I pop the drum on after a few 10rnd stick mags ;) )
    -Convertible to a pistol format** (by virtue of the receiver being constructed a 'firearm' per current ATF regs ;) )
    -Externally-visible Degtyarov-inspired gas operated locking system


    *This is to try to disabuse new, ignorant shooters of 'Assault Weapon' sensitivities
    **This is to try to inform new shooters of the asinine nature of NFA/ATF classifications rules
  2. Tophernj

    Tophernj Well-Known Member

    Personally I like the idea of the safety being just behind the mag.

    Cool concept. What will it be chambered in?

  3. barnbwt

    barnbwt Well-Known Member

    It's slated for 7.62x25 at the moment, though I think it will end up (for now) in a 223 brass-based version of Tokarev (not much left, and too spendy). Probably close enough the x25 can still be fired safely, but with a fatter neck so the 223 brass' thick walls won't need finish reaming after necking down.

    The buttons right behind the mag are currently the mag releases; do you think it'd be a better spot for the (manual) safety? Where would you reposition the mag release?

  4. barnbwt

    barnbwt Well-Known Member

    I could really use the opinions, ya'll. Think of it as your chance to make history, for no pay! :p

  5. barnbwt

    barnbwt Well-Known Member

    No takers, eh? Kinda tight-lipped around here, for once... ;)

  6. Nom de Forum

    Nom de Forum Well-Known Member

    Give me some more time to reply. I looked at it within minutes of your posting it and think it deserves serious consideration before comment. Unfortunately I have been delayed due to being busy investigating historical comments in posts and PMs with reasonable minds, and receiving unrelated insulting PMs from an unreasonable mind. What I can say is the intention of your design is very admirable.
    Last edited: May 2, 2014
  7. WestKentucky

    WestKentucky Well-Known Member

    I would like to see it bottom eject.that way it doesn't bother either lefty or righty. No need for fancy buttons and such, besides if your trying to have reversible extractors, what happens if both go active? Would be a nasty stovepipe to clear. An oversized mag well should let you bottom eject to the side of the mag with no issues, if you wanted you could make a double-wide mag with one side hollow and bottomless to eliminate loading issues where there's an extra hole.
  8. Nom de Forum

    Nom de Forum Well-Known Member

    Did you by any chance post this thread just to give all of us a headache?

    That is going to be really hard to do and gives me a headache just thinking about it. Is this feature really necessary?

    How will the safeties actually prevent discharge? Will they lock, block, or redirect the firing pin? That would be a good feature.

    What do you anticipate the weight will be with a stock and forearm attached? You state you want to keep the weight down, so why wood and not a synthetic stock and forearm? Synthetic does not have to appear military. Are you also going with wood because it is easier for you to personally create?

    Consider making a folding charging handle ala HK91 to clean-up the appearance and eliminate snagging on hands and arms.

    Ok, that's all for now. I've got to go take some aspirin.
  9. primalmu

    primalmu Well-Known Member

    I might be off base here, but I feel like an SKS would fit the bill just as well, and would be cheaper to buy and cheaper to feed.
  10. barnbwt

    barnbwt Well-Known Member

    "I might be off base here, but I feel like an SKS would fit the bill just as well, and would be cheaper to buy and cheaper to feed."
    Won't even dignify that with a response...just kidding ;). This is the first from-scratch design I'm going to bring to fruition; off-the-shelf isn't even an option for me, that's not the real purpose of this exercise. My first design was a tilting-bolt action that was actually markedly similar to the SKS, but I quickly found the design doesn't play will with drums, which was a deal-breaker. The SKS is also a vastly larger and heavier rifle than what I'm going for, being a full-size battle-rifle type gun. This one's a definite plinker, more like an M1 carbine but with better magazine capabilities.

    "Did you by any chance post this thread just to give all of us a headache?"
    Eh, I stopped noticing the migraines a few months back :D

    At the risk of losing my 'million dollar idea,' (;)) I've attached a few more operational/detail pics of relevant parts to clarify what's happening.

    "if your trying to have reversible extractors, what happens if both go active?"
    The extractors are at 10:00 and 2:00 (or ejectors at 7:00 and 5:00) so I ASSume a dual-activation would throw the brass straight up or damage one/both extractor (I'd obviously try to design the hook contours to avoid the latter). The design was originally a straight-up ejection, with lines based roughly on the PPSH-41 (also in 7.62x25, but a direct blowback action that left the rifle heavy, harshly recoiling<compared to a locked breech>, and with a terrible trigger), but scaled to something more the size of a "tactical pistol" (Skorpion, MAC10, mini Uzi, etc.). My design progressed to an 'open' action that allowed for a very large ejection port up top, so I figured why not try to get the rounds to deflect to either side and make the gun even more ambi-friendly? Since vertical ejection is a compromise that favors neither, and may irritate/disturb new shooters trained on the front sight :)

    "Is this feature really necessary?"
    No, but I think it's easier than I expected at this point. You either:
    1) Have two pivoting extractors, and have a bump on their tails that engages a selectable lever when the bolt retracts, which would cause the selected extractor to pivot up off the rim of the case just as the fixed ejector punches the far side of the case head
    2) Have a single extractor claw in the middle, and to parallel plunger ejector pins in the bolt. Only instead of being driven by a stiff spring, they contact a rigid surface (the back of the receiver tube) at the end of the bolt's travel, at which point they act like a fixed-blade ejector to aggressively punch out the spent case

    It's complicated to describe, but would be extremely easy to understand/operate in practice (assuming it works well), and really only adds two extra parts (the extra ejector or extractor, and a selecting lever)

    "How will the safeties actually prevent discharge? Will they lock, block, or redirect the firing pin? That would be a good feature."
    There is a sliding safety that protrudes into the thumb web when active. When slid forward (it's more positive than a grip safety) it will cam the hammer back off the trigger/sear, and lock the trigger/sear into place, and slip over the same sear surface as the disconnector to alternately block the hammer if the primary part failed, somehow. The grip safety will simply interfere with the trigger's movement until it is depressed. The trigger itself is a little different than what we're used to; it's a two stage where the first stage it pivots under little load, and then slides straight backward off the sear contacting nothing but the sear, the pivot pin, and the shooter's finger. The hammer and trigger are similar to a Giesselle AR15 format (i.e. AK47 ;) ). Disconnector is a hammer-actuated sliding type that does not bear on the trigger except during reset. Should be a very nice trigger if I can make it good quality :cool:

    As far as firing pin safeties, the locking piece actually retracts the firing pin mechanically when it moves backward (just like the Degtyarov) making a very effective OOB safety. There is no pin safety when fully in battery, which is why I am considering making the bolt hold-open lever on the foregrip actually pull the bolt/carrier backwards a fraction to block the firing pin, when not depressed by the shooter's weak hand. Other than the need for ejection selection, the grip safety role could be filled by such a device. I am undecided though, since such a design that requires two hands to operate is a limitation I'm not certain is a benefit (to new shooters, yes; to me, perhaps not; to me drawing the rifle from a scabbard, absolutely)

    "What do you anticipate the weight will be with a stock and forearm attached?"
    About 1lb of that is just the barrel, btw, which I think is a really efficient ratio :). The real question, is what do I anticipate the weight will be with a full 71rnd drum attached :D. The stick mags ain't lightweight, either (I'd have a ten-rounder made up for walking around, most likely). The stock I'm using is another few pounds, so my hope is for ~6lbs or so with a mag but no ammo at the end of the day.

    "Are you also going with wood because it is easier for you to personally create?"
    Yes. Exactly that. The stock could be a pretty low-density affair with a hard finish, since this gun isn't exactly meant for hard recoil or butt-stroking. Cyanoacrylate-sealed Basswood would probably work, but for now, I'm using the chopped up pieces of a Steyr M95 stock (it's not suited for the recoil of 50 Alaskan that the action is being rechambered to ;) ) to form the butt and foregrip. See attached (early) mockup pic.

    "Consider making a folding charging handle ala HK91 to clean-up the appearance and eliminate snagging on hands and arms."
    I liked the idea and was planning on it some time back, but then I found out about how much everyone hated the Reissing's flush folding handle in the foregrip, which is exactly how I'd planned to do mine. Kinda soured me on the whole concept of a 'hidden' handle, but if you can think of a better solution please speak up. Maybe make the 'swell' (or whatever the German word for it was) at the tip of the foregrip into a knob or ring that is grasped to cock the gun?

    What's more odd about the foregrip design, is that when the charging handle is pulled back to cock the gun, it will automatically hold the bolt open. When the handle is allowed to return fully forward by a return spring and then grasped by the weak hand, the bolt catch will disengage and drop the bolt into battery. Again, sounds complicated, but makes total sense; the bolt locks back when you manually pull it back to check or on an empty mag, and only releases when you grip the gun to shoot it. Not ideal for chambering a round quietly, but that's what the system of safeties is for: cocked and locked carry in a rifle :cool:

    "Did you by any chance post this thread just to give all of us a headache?"
    Maybe. I undertook this project with the intention of making a gas-op locked-breech pistol caliber carbine, since there are very few out there (MP7, MPX, and that's about it if you aren't counting cut-down ARs/AKs). But, drunk on the total freedom a scratch design carries, I thought I should re-examine the very foundations of weapon ergonomics that, I felt, were rooted more in long-extinct designs (bolt action handles, selector levers) than in what is intuitive. Gunnie version of navel-gazing, I suppose ;)


    Attachment Key:
    1) FCG Concept (proof of concept soon to follow, hopefully)
    2) Very early mockup of the parts I had at the time
    3) Older-configuration view of the large ejection port and exposed action with a VZ52/Garand FCG (possibly bad for debris, but great for demonstration)

    Attached Files:

    Last edited: May 2, 2014
  11. barnbwt

    barnbwt Well-Known Member

    I've at least convinced myself that, no matter how the bolt/safety design shakes out, it will not have much impact on the receiver tube, proper. Therefore, I've decided to proceed with cutting metal for the locking recesses, mag/ejection ports, and FCG opening. I can pretty complete the rest of the project without any extractor or ejector, and solve those problems once the rest of the platform is set in stone (or steel, to be specific).

    "An oversized mag well should let you bottom eject to the side of the mag with no issues, if you wanted you could make a double-wide mag with one side hollow and bottomless to eliminate loading issues where there's an extra hole."

    Don't know how I missed your comment earlier, but thanks! In this case, I can't eject down by the magwell since I'll have drums in the way, and the PPSH stick mags actually have little 'ears' on their sides to emulate the top surface of a drum. But... one of my side projects is a belt-fed VZ58 conversion, and the idea of ejecting through a hollow magazine may be the solution to my ejection dilemma. I cant' eject up since the belt and top cover are in the way, but I don't need the magwell for anything but to hold the RPD drum box in place. So there's no reason I can't remove one of the side walls of the 'feed tower' sticking off the top of the box to latch it into the magwell, and figure out how to get rounds to go down instead of up (probably just removing the extractor would be the easiest solution for a simple conversion, probably modifying the bolt head for a bottom-claw extractor in the slot the blade ejector used to go, and a button-type ejector on the opposite side or where the extractor claw used to go). But that's for another thread :)

  12. Nom de Forum

    Nom de Forum Well-Known Member

    I agree a flush mount would be disliked. What I notice from your diagrams is how short the forearm is and how big the cocking handle is sticking out from the bottom. It is not very aesthetically pleasing IMO. There is very little room for the hand next to the cocking handle. When you attempt to zero the cocking handle is going to rest on the sand bag and not in a good way. How about extending the length of the forearm, place the a folding cocking handle at the end of the forearm but not flush inside it. The shooter would then extend his arm more but his hand when shooting would have more room. There would be no interference from the cocking handle when resting the rifle on a sandbag for zeroing. What I envision is a cocking action similar to a under-lever air rifle but without the long lever or flush mount. The cocking lever would have a the casual appearance of a gas tube under the barrel at the end of the forearm. Now that I have discovered justin22885's thread about designing a new rifle, which you have contributed much, I am grateful to only have a headache from thinking about your thread and not a stroke from justin's thread.
  13. barnbwt

    barnbwt Well-Known Member

    There's no way I'm extending anything on this rifle :D. I'm trying to keep it as light and compact as possible, since that was an original design goal (to make a locked-breech carbine capable of shooting high-end pistol-class rounds like 10MM or 9x23 and significantly more compact than an AR pistol-caliber conversion) and because it also works well with the introductory carbine/bantam carbine/trail carbine roles. Heck, I fully expect to SBR the thing back to the receiver tube eventually, for something about the size of an MP5k with a much more compact receiver/lower and much higher cartridge power capability.

    "It is not very aesthetically pleasing IMO"
    Indeed. Indeed :(. The index finger actually sits in front of the handle during shooting so it's a lot roomier than it looks. Thinking along the lines of a BB gun pump handle (mine were lever action as a kid :D) I think it'd be possible for the handle to fold forward into the schnabel forearm* and be mostly hidden but for the tip which would stick out the front and be readily snagged by the index finger for cocking. The new shooter would be less likely to try to pull back on it while shooting, too (my primary concern with its current location all along). While it's locked in place by the bolt catch lever, if that is released during firing, tension on the cocking handle would pull it back some and the returning bolt carrier would smack the hell out of the shooter's finger :(.


    *Man, that word's been killing me for like two days :D
  14. Ro1911

    Ro1911 Well-Known Member

    Why not just make this a 9mm and use Suomi mags? Or make it 7.62x25? I don't get the appeal of making it a wildcat 223 thing that only you and your handloading buddy's are going to like, 7.62x25 is available at about the same price as 45 and 9mm is cheap usually.

    Plus 9mm doesn't have a neck which is good for reloading if your so inclined
  15. Nom de Forum

    Nom de Forum Well-Known Member

  16. barnbwt

    barnbwt Well-Known Member

    "Why not just make this a 9mm and use Suomi mags? Or make it 7.62x25? I don't get the appeal of making it a wildcat 223 thing that only you and your handloading buddy's are going to like, 7.62x25 is available at about the same price as 45 and 9mm is cheap usually."

    PPSH mags are awesome since they are straight-line single feed, which is probably the most reliable type there is, and the extra length they have over the original Suomi design allows for a ton of cartridge options. At 9mm length, you're basically relegated to 9mm, and have a very hard ceiling on the power levels you can develop. The PPSH length can accommodate 10mm length offerings, if I remember correctly (with shorter bullets it for sure can) and the sticks can feed 45acp with lip alterations (40cal is about as much width as the drums can accommodate without massive modifications)

    9mm will feed from PPSH mags (not drums, though :() and a spacer/adapter for the mag well could probably allow it to take the shorter Suomi mags (sticks, drums, and coffins :) ). It is in 7.62x25, but the surplus ammo is now so expensive and often unavailable, and reloadable factory ammo even more so, that folks are looking back at converting 223 brass into tok brass. The problem is the case body is thicker when trimmed back that far, so tedious neck reaming is required. I thought, "why not just make the neck of a tok chamber a few thousandths thicker so you don't have to do that?" Now you have a ready supply of convertible, cheap brass, that's also capable of 223 pressures (60ksi vs 35ksi for 7.62x25) which might make for very interesting ballistics from such a small cartridge/rifle. Moreover, aside from the extra neck room possibly allowing already-split-prone necks to split and 'ruin' unreloadable brass, there's a very good chance standard 7.62x25 would work just fine.

    "I was thinking two or three more inches"
    The receiver tube is 10" long; that's a 20-30% increase in the core part of the gun I can't chop off for an SBR. Also, the fact there's a drum there means your hand has to be at a 90deg angle to get around it, so a diagonal grip that takes more room on a foregrip isn't as necessary as a longer rifle.

    "Sorry, you asked for opinions and think you want sincere ones."
    You misunderstand; I never particularly liked the look of the cocking handle down there (check out a FAMAS or early AR10; it never looks good). It was always the biggest aesthetic compromise on the gun by far (well, the square tube receiver is a close second ;) ) but I just couldn't see a good safe place for a reciprocating handle anywhere, or a place to put a non-recip handle that wasn't jutting out the sides or into the line of sight. That left the bottom, and specifically the foregrip.

    Ooh, here's an interesting idea, borrowed from Czech heavy machine guns; slide the foregrip forward to snag the bolt carrier, and pull everything back until it releases at the very end. Maybe an ambi-detent button on either side you have to press to unlock the grip and slide it forward.

    "I think you are on the right track with this idea and should abandon the gaff hook."
    Abandon the hook for a forward-pointing "sinister beard"; got it :D. Only possible problem I'd have to watch for is that reaching past the foregrip tip is really close to a barrel that may have just had at least 71 rounds dumped through it. Would have to keep ergonomics in mind (they are touchy enough already since the gas release port is at the first set of lightening cuts above the thumb/index fingers, but at least the cuts are smaller than finger tips :eek:)

    Last edited: May 4, 2014
  17. barnbwt

    barnbwt Well-Known Member

    Great feedback, guys, keep it coming. I'm glad the overall concept of the rifle sounds like something worth pursuing :cool:. Just gotta get the little details where most folks would probably like them and I think I'll have a winner.

  18. henschman

    henschman Well-Known Member

    Cool idea overall, but I would never own a rifle with a grip safety, and would certainly never use it to teach new shooters. For classic field position type shooting, like we teach at Appleseed, we teach that the only part of the trigger hand that is putting pressure on the grip is the bottom 3 fingers, pulling the grip straight to the rear to keep the stock in the shoulder pocket. Furthermore, we frequently have shooters rotate their hand around the stock so their thumb isn't wrapped around the "wrist" of the stock, to keep their trigger finger from "dragging wood." I wouldn't want to encourage the type of gripping that would be necessary to actuate a grip safety on a rifle.
  19. Nom de Forum

    Nom de Forum Well-Known Member

    It will be interesting to read barnbwt's reply to your post. Until then, I don't think this rifle is intended "for classic field position type shooting". It is my impression it is being designed for the pleasure of creating an unorthodox design and for users who are very inexperienced, like the safety features, are interested in plinking and self defense with something more exciting and powerful than a .22, will most likely never be interested in "classic field position type shooting, and want something relatively inexpensive. I also have to wonder if barnbwt's grip safety design will cause the same number of problems with accuracy as the grip safety on a Colt Gold Cup. That number being 0. If done right, barnbwt's grip safety may have the same number. This is just my impression and I really hope barnbwt will soon provide clarification.
    Last edited: May 5, 2014
  20. briansmithwins

    briansmithwins Well-Known Member

    For absolute ambidexterity in ejection consider using a system like the FS2000. There is a ejection tube that parallels the barrel. Empty cartridges are placed in the ejection tube and drop out near the front of the forearm, out of the way.

    For ambidexterious charging, I'd consider a pump forearm as it's easily worked by either hand.

    Grip safeties and firing pin blocks are generally overkill for long arms. Each thing you add increases complexity and cost while reducing reliablity.


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