technical discussion for the function and design of self-loading rifles

[Tirod]

Why does it have to eject anything at all?

About twenty years ago a working full auto was designed to simply shove the empty case ahead of the next, becoming the projectile that was powered by the one behind. Rather massive hollow point, but that was the first gen - just fire "blanks" and keep shoving another loaded case into the barrel.

By the way, what's the range and target of this mythical gun? Those parameters have a lot to do with the ballistic requirements, and those drive a lot of the design decisions.

 

[barnbwt]

Careful Jason, if some of these ideas are patentable, some schmo or corporation will snap them up if you get too specific...

I think the firearms industry is worse about this than any other. If you think any of your ideas are "novel" and show any promise as a viable design, you should think about getting at least a provisional patent. There's no profit in just giving your ideas away...

I'm pretty sure every one of today's "big players" got there by ripping off and undercutting each other prior to a big war's contracts (there's no "for shame" smilie)

Your floating chamber idea almost sounds like short recoil; the chamber is like the pistol barrel, and the bolt is like the slide. If you could ensure the bullet can jump to the barrel from the chamber piece before it begins to move, you'd end up with a very compact action. The trick would be to keep the bolt/chamber together long enough to ensure ambient chamber pressure. It would be tough to keep the two together under the stress of anything larger than a pistol cartridge without a locking mechanism, which would turn the design into a sort of delayed blowback, I suppose. A delayed locking device would allow you to use higher/longer pressure spike rounds, like intermediate rifle calibers. It's a cool concept, sounds very simple and compact, would probably make for a good subgun.

But unless you are chambering your action for an intermediate cartridge, delayed blowback may be difficult. The more powerful the round, the greater the delay needed to get safe pressures. Since delayed blowback locks typically depend on bolt mass and mechanical disadvantage, I always either end up with a really heavy gun, or extreme ammo sensitivity (easy short-cycles or case-destruction outside of "ideal" chamber pressures) when I run the math.

In my design musings I always found it more convenient to utilize tapped barrel gas, since it can be regulated by orifices unlike chamber gas in a blowback action. But if the rounds you are firing are smaller (I think there's a ratio out there for bullet/bolt mass) there is hardly a more efficient lock mechanism than delayed blowback or short recoil.

I'm glad there are folks out there still interested in innovating new concepts for these ancient weapons. Gun actions make for great thought experiments, don't they? Seems like everyone and their brother has been making the same half-dozen guns lately. People even identify their firearms by the guns they were copied from (AR, AK, 1911, etc). Just like good art, a good design shouldn't be purely derivative.

TCB

 

[Driftertank]

The HK delay system actually uses a wedge piece attached to the bolt carrier to cause lock-up, by means of the bolt carrier moving forward relative to the bolt head under both recoil spring pressure and BC momentum.

I would try to design some sort of similar camming action into your lever, as opposed to a (i'm guessing fairly small) spring. Small, high tension springs tend to fatigue fairly quickly, in my experience. I think by making it a positive mechanical actuation, you'll make it more durable and reliable...

 

[jason41987]

where would the tension on the lever be gained from with a cam action?... hmm, wonder if theres some way to use pressure from the mainspring to apply tension to the levers?

also.. lever-delayed blowback, and floating chamber designs are already out there... nothing for me to steal, just adapting whats already there at this point.. if i come up with anything particularly useful i promise no one would know about it

ive never heard of pushing an expect casing out the front... it just seems difficult to do...

i guess the best way to not have to eject something is to somehow encase the powder into the cartridge base like the old volcanic pistol did.. but energy would be so small...

i wonder if its possibly to develope some kind of perishable casing... maybe.... i know old muzzleloaders used nitrated paper to hold powder and a bullet for quick reloading.. if it was some how possible to stiffen the the nitrated paper so it remained rigid in a way that it would completely burn up upon firing.. would just need a chamber that was sealed from pressure.. and for safety purposes i would only cycle something like this via a gas piston and a rotating bolt...

umm, certain pine resins are very high in heptane, which is highly flammable, can be used as fuel.. with these sticky resins one could make a glue... possibly using this glue to coat and stiffen a nitrated paper cartridge could possibly create a consumable paper cartrdge that might just be stiff enough to handle being stuffed in a magazine, and fired from a rifle

anyone have advice on an inexpensive rifle easy to work on and not a major loss if one of these ideas were to fail? (fired remotely of course).. or it might be better to come up with a single shot platform with a thread-on breach for testing... like a threaded rifle barrel.. load a cartridge, then screw on a threaded steel cap with some remote means to fire it for testing experimental and wildcat cartridges

 

[Rail Driver]

If you're looking for a inexpensive, but robust rifle to test theories out with, get a case of Mosin/Nagant rifles. They don't get much more robust or cheap than that.

 

[jason41987]

one thing i made for a black powder firearm.. was i made the black powder by grinding all components into a fine powder, mixing them to the proper 75/15/10 ratio with a bit of distilled water... moulded it into a tube, and it remained rigid when solidified... i believe they do the same thing with smokeless powder (nitrocellulose) to make caseless ammunition... its basically like mixing concrete and letting it dry solid.. and can be moulded to hole a bullet and primer

question is.. what happens to the primer when its fired? does it just fall out the barrel? or drop out of the rifle when the actions cycled?.. is the primer consumable as well? i didnt have to worry about that in a muzzleloader

 

[jason41987]

rail... i think ill just machine a breach section for a standard remington 700 barrel.. just a piece that can be threaded over the barrel itself with a some remote-means of firing it.. i just wouldnt have any need for a stock, sights, trigger group, etc as it would all be clamped down to a bench or table

 

[kozak6]

What is the purpose of the self loading rifle under discussion?

Direct blowback operation is only suitable for pistol caliber cartridges. Recoil operation is generally considered obsolete as far as shoulder fired automatic weapons go, but could be an option for a heavy caliber such as .50 BMG. Gas operation is probably the most suitable for a centerfire shoulder fired semiautomatic rifle.

Direct impingement is suitable for a "sniper" or designated marksmen's rifle. A gas piston (either type) is probably better for a general issue rifle, although this is open to argument.

In practice, delayed blowback actions tend to be fussier about ammo. For a military, which might only supply one bullet weight, this isn't an issue. On the other hand, a civilian reloader would be infuriated by an action that would only function with a limited variety of bullet weights and that might destroy brass.

Magazine type depends on the purpose of the rifle. A fixed box magazine would be a bad choice for a light machinegun. Belt feed would be a poor choice for a sniper rifle.

Furniture depends purpose.

Caliber depends on purpose.

Although you sorely neglected to mention it, bullpup or not is another contention to consider. Once again, it depends on the purpose of the proposed rifle.

Being a monetarily impaired individual, the perfect semiautomatic rifle if I were to design it, would be something like the top half of a Leader Arms carbine (simplified AR-18) combined with a plastic lower such as a PCF or Cav Arms.

 

[jason41987]

purpose of the discussion is to discuss all options and design features of whatever youd like to discuss

 

[jason41987]

anything else anyone would like to discuss?

 

[45_auto]

i guess the best way to not have to eject something is to somehow encase the powder into the cartridge base like the old volcanic pistol did.. but energy would be so small...

i wonder if its possibly to develope some kind of perishable casing... maybe....

Ever heard of re-inventing the wheel? A little research will save you an immense amount of time - you may want to look into caseless ammo and combustible cartridge cases - both have been around for a long time in modern forms.

Hint- take a look at an H&K G11, or a M829 120mm cartridge.

 

[jason41987]

HK G11 uses a powder mixture mixed and packed into a mould to dry into shape.. but is quite brittle, paper cartridges were used in civil war era muzzleloaders...

for caseless ammo.. why dont they use both?.. start with the solid propellant wrapped in a nitrated paper held together with some type of combustable resin.. would be durable enough to cycle through magazines, be tossed around a bit... and be entirely consumable.. thats what i would do if i was going caseless.. but its certainly a touchy technology to get into, wasnt even me who brought it up though

 

[Autopistola]

How come nobody uses a gas retarded system on a carbine, similar to the HK P7 pistol? You could mount the piston above the barrel to keep the hanguards from getting obscenely hot.

I would like to see a carbine that uses a (mostly) vertical block that delays opening, then is cammed out of place by raceways on an op rod/bolt carrier.

 

[jason41987]

do you mean like a falling block in an 1885 single shot, but semi automatic?

 

[Autopistola]

I mean a a semi-auto carbine with a bolt locking block, roughly borrowing the idea from an AVS-36.



My thinking was that this could be rearranged somehow, instead of between the magazine and breech face. The locking block could be U-shaped and fit around the barrel; and an op rod could unlock it. If nothing else, it could be there for mechanical disadvantage.

 

[jason41987]

that reminds me of what john browning did on the 1886 lever action.. used vertically moving lugs like that to lock the action... that would be very easy to work out though... just have the bolt carrier push it down by running over the top of it with an angled section to push it down, and then continue pulling the bolt to open it...

i doubt it can be moved rearward though, it would have to lock the bolt and in order for it to lock the bolt it would have to extend backwards beyond the magazine which also means a longer bolt carrier and more weight.. probably better off with it in front, but somehow out of the way, like off to the sides....

the russians scrapped this idea because it was pretty lousy in practice

hmm.. does a carrier actually open the lug on that, or does the gas system itself unlock it and allow the bolt to be pushed back from gasses in the chamber?

 

[mr.trooper]

Guns are simple machines. The FCG is the most complicated thing on most firearms, and even that can be understood by the average user if they take some time and study a decent diagram.

With that in mind, what does it really matter what kind of operation a gun uses? They all have their trade-offs, and as long as you maintain them and use the right kind of ammo they pretty much all work.

 

[barnbwt]

Guns perform a simple function, but the few parts that comprise them have suprisingly complicated interactions.

I like the idea of a vertical drop locking device, seems like it could be scaled to hold back a wide variety of cartridges since the lock itself doesn't depend on the cartridge's pressure level or bullet momentum. However, since the falling element is outside the bolt/chamber assemblies (unlike rotary locking lugs) the reciever will have to be beefier where it braces the falling block, right? Seems it could make the gun heavier if not done right. I wonder if it might be safer though, since a firing pin safety based on the position of the block would be a guarantee of full lockup before ignition.

TCB

 

[jason41987]

barnbwt.. are you saying have the falling block portion with a firing pin hole in it so that unless that block is fully locked, the firing pin wont move?... or if it was partially closed, there might be enough force in the firing pin to close it and still ignite the round, or otherwise not fire at all?.. that does seem pretty safe....

would this design be gas operated with a bolt carrier acted upon by gas forces, in which case it can slide under an angled portion of the block and lift it, or push it down before dragging the bolt along,

or would this be a type of gas-delayed blowback system that uses gasses in another chamber to push the block away, allowing the bolt and cartridge to blow back without the partial extraction before cycling?

 

[barnbwt]

Like any bolt lockup, energy from gas or recoil/blowback can unlock the mechamism. But since the force needed to disengage a falling block is totally perpindicular to the line of action of recoil, it could remain locked without any other consideration as long as it takes to get safe pressures (you can reload a lever action as slow as you want) which gives you more flexibility when it comes to timing the unlock/eject sequence. I've always wondered if anyone ever tried unlatching/cycling a bolt with the return stroke of the piston, since pressures have to drop before it can move forward.

As far as the pin safety, I was just saying it would be easy to rig something up to make the latch itself double as the trigger disconnector, which seems like it would be more Murphy's Law resistant. What you described seems like it would work, you just want to be sure that block doesn't try to fall while the pins in it.

I wonder if you build everything into the block like we do with the bolt nowadays, and use the bolt carrier to rip out the round once the bolt/block drops clear. Sort of like a miniature howitzer I suppose.

TCB

 

[jason41987]

thats starting to sound overly complex for a design, because if everythings in the locking block then its difficult to recock the hammer, eject the catridge, load a new one

 

[jason41987]

any of you see the gas delayed blowback systems such as those in the H&K P7 i believe it was?.. ive never seen one of these personally... but apparently theres a second chamber near the barrel... when the guns fired, this chamber gets pressurized and pushes agaisnt the piston, which has a spring against it.. as long as theres a certain amount of pressure in this chamber, the bolt wont move.. but as soon as it drops the spring pushes the piston forward again and opens the action to cycle...

am i understanding the way this action functions properly?.. or am i missing something?

 

[barnbwt]

That HK is a clever little thing, from a number of moving parts perspective. It's really about as simple as a direct blowback.

Given the power available from a gas tap, I think this setup could be strong enough to delay a rifle cartridge at peak pressures, but I'm not sure if rifle pressures drop fast enough to work well safely. It seems with this gun that once the pressure gets low enough that the spring can over come it, you would want any remaining pressure to be gone immediately.

That little remaining pressure is what has to extract the casing and move the heavy bolt, I'm not sure if a near-ambient residual pressure would be strong enough. You wouldn't want that cartridge coming out of battery with even hundreds of psi still left in it, but that may be what it takes for Force=Pressure*Area to be high enough to reliably cycle a rifle action. I wonder if that pistol may be simply a slightly delayed blowback in reality.

Unless you can find a way to quickly vent the chamber once it picks up momentum (but before it vents out the ejection port), I think you'd still need a postive mechanical delay for something more powerful than a mid-size pistol cartridge. If you allow the barrel-piston to shift forward a bit under pressure , you could have it charge a spring that would fling it back more assertively once pressure drops enough.

TCB

 

[jason41987]

are you saying the gas pushes the piston forward, and somehow that locks with a carrier that once the gas is gone moves back from spring pressure.. then disconnects as the mainspring returns the bolt forward?... seems like a gas system that operates on the return stroke

 

[barnbwt]

Pretty much

I just don't think a delayed blowback can be made to function with high pressure rifle cartridges, at least that's the cureent state of things. By using the gas delay to carry the bulk of bolt thrust load at peak pressure, I imagine the gas operated lock wouldn't need to be as over built, though.

I guess the solution to a delayed blowback rifle may be a combination of delaying/locking methods, which doesn't necessarily over complicate the design.

TCB