This has been discussed in the past, but it's time to start taking about it again.

The Modular weapon system for homebuilders. aka the "Weaponeer Project"

The project is based on the Stoner 63

Background:

The Stoner 63 is an American modular weapons system designed by Eugene Stoner in the early 1960s. It was produced by Cadillac Gage and used in very limited numbers in Vietnam by members of the United States Navy SEALs

Operating mechanism
The Stoner 63 series of weapons are gas-operated, air-cooled belt or magazine-fed and fire from the open bolt position to prevent cook-offs and enhance cooling. The weapon has a rotary bolt locking mechanism with 7 radially symmetrical locking lugs that engage a series of recesses in the barrel extension, and is actuated by a conventional long-stroke piston. The radial arrangement of locking lugs distributes the firing load evenly around the bolt head and barrel socket, reducing stress and increasing the longevity of these critical components. Attached to the piston extension is the bolt carrier which is equipped with a curved cam track that guides the bolt's cam pin (retained by the firing pin) and rotates the bolt 22.5° during the movement of the piston to either lock or unlock the bolt from behind the abutments in the barrel socket. Incorporated into the bolt carrier/piston group is an anti-bounce device, consisting of a 4 in (101.6 mm) carbide rod that rides within the piston extension’s hollow interior and moves back and forth during the recoil and counter-recoil cycles, reducing bolt bounce and preventing the possibility of firing out of battery during closed bolt firing (in the Rifle/Carbine models).

When fired, propellant gases from the ignited cartridge following the projectile down the bore are vented through a gas port into a gas cylinder where they drive the piston and bolt carrier rearward. There is about 0.2 in (5.1 mm) of uninterrupted free travel calculated to permit the gas build-up in the bore to drop to a safe level before the carrier's cam slot rotates the bolt counter-clockwise to unlock. The locking lugs have no pitch therefore no primary extraction occurs during the unlocking sequence. A deeply-seated spring-loaded claw extractor in the bolt head extracts the spent cartridge casing from the chamber and a spring-powered ejector fixed to the front feed mechanism trigger housing ejects the casing. The bolt carrier continues to the rear and compresses the recoil spring on its guide rod.

The Stoner 63 has a unique buffering system contained within the bolt carrier. In front of the carrier cap are a steel shim and a set of 27 saucer-shaped Belleville washers oriented in opposing sets of three, which absorb energy from the piston stroke by deforming into a flat plate when the bolt carrier strikes the receiver’s end cap. When the plates return to their original shape they release a pulse of strain energy which propels the reciprocating parts forward in counter-recoil with a speed only slightly below that of the original recoil velocity. This feature was designed to extend the weapon’s service life, and the plates will function without failure for between 40,000 and 50,000 rounds (depending upon the type of ammunition used and cyclic rates employed).

Feed
 
A detailed view of the Stoner 63 feed tray.
The magazine-fed Stoner 63 Rifle.In the belt-fed configuration, belt movement is produced by a roller riding in the channeled feed arm and is actuated by the reciprocating movement of the bolt. The spring-loaded feed arm is protected by a hinged top cover and is pivoted at its rear end. As the bolt travels back, the front end of the feed arm moves across the feed tray and operates a lever attached to a single set of spring-loaded pawls. These pawls move a cartridge and link over the feed tray’s stop pawl from where they are positioned onto the slotted feed path and held firmly in place by a spring-powered steel plate in the top cover. The cartridge is then pushed out of its link and the empty link is discarded through the link ejection port which is held closed by a spring-loaded dust cover.

The Stoner 63/63A is chambered for the now-standard 5.56x45mm intermediate rifle cartridge. When in the belt-fed role, the weapon would feed from a disintegrating metallic linked belt marked "S-63 BRW" which is a scaled-down version of the U.S. M13 link developed for the M60 GPMG. The Stoner 63/63A will not work reliably with the later M27 link developed for the M249 SAW. The belt is normally contained in a 150-round plastic ribbed container that has a tab allowing it to be clipped on to the side of the left-hand feed tray. Early ammunition boxes were olive drab in color and manufactured at Costa Mesa, this later changed to a black-colored plastic container made in Warren, Michigan. Stoner 63A boxes were also black but had a reduced capacity of 100 rounds as the larger container would unbalance the rifle. These can either be attached to the left-hand feed tray or held in a bottom box carrier when using the right-hand feed mechanism. Several drum-type belt carriers were designed for the left-hand feed system, with a 150-round drum container being the most popular and used frequently by SEALS in Vietnam. A 250-round drum carrier was also developed by NAWS China Lake, but this proved too heavy and cumbersome. SEALS would also resort to converting RPD belt carriers for use with their Stoners. The detachable magazines used in the Rifle, Carbine and Automatic Rifle models are fabricated from steel and weigh 8 oz (230 g) unloaded. In an effort to reduce weight, aluminum magazines were later developed cutting the weight down to 4 oz (110 g). Standard magazines have a 30-round cartridge capacity but a 20-round magazine was also offered.

Barrel
 
The Stoner 63 has a quick-change barrel that is retained by a spring-loaded latch near the feed cover (visible on the left).Barrel interchangeability is one of the main features that provides the Stoner 63 platform its outstanding versatility. There are 5 barrel options available for the system: the Rifle, Carbine, Automatic Rifle (AR) and two types of machine gun barrels, a standard heavy barrel and a short Commando tube. The standard machine gun and AR barrels are 20 in (508.0 mm) in length (not including the flash suppressor). The Commando barrel has a length of 15.7 in (398.8 mm) and is fluted to reduce weight and enhance the barrel's cooling characteristics. This version was sometimes used by the Navy SEALS but was never fully reliable as the gas port is near the muzzle and as soon as the bullet leaves the barrel, gas pressures drop drastically leaving the operating system little to no power reserve. The gas port was drilled larger in an attempt to alleviate this problem; however this had the effect of merely accelerating the piston's initial displacement. The issue was never truly resolved. The Rifle, Carbine and AR barrels have no gas valves as they are exclusively used in magazine-fed configurations and do not require the energy surplus levels of belt-fed mechanisms. The standard machine gun barrel has a manually adjustable gas regulator that can be operated by inserting the nose of a cartridge into a hole over the regulator’s lock detent, pushing down on the detent and rotating to the desired position. The gas regulator has three settings: a "slow" cyclic rate of about 700 rounds/min, produced when the narrowest indicator notch is set over the detent; a middle position with an intermediate rate of 830 rounds/min and a third "fouled" position that delivers the largest quantity of propellant gas to the system, resulting in a rate of fire of 865 rounds/min (the use of this setting should be limited as it induces excessive wear on the operating mechanism).

All Stoner 63/63A barrels have a quick-detach capability and can be removed in a matter of seconds in field conditions by simply pushing down a latch located on top of the weapon in front of the feed cover and pulling the barrel forward (with the bolt retracted). The chamber portion of the barrel rests on a U-shaped barrel bracket attached to the gas cylinder. The barrel is firmly locked in position by means of a spring-loaded latch (with two nested coil springs) which drives a steel pin into a hole in the barrel socket. All barrels have a gas block to which a bayonet lug and front sight assembly are mounted. The barrels are equipped with a bird cage type flash suppressor with six oval ports. The AR and standard machine gun barrels also have a carrying handle that can be snapped into one of three positions or removed altogether. The black-painted wooden handles are attached to a steel rod via roll pin. With a few exceptions, all the barrels used in the Stoner 63/63A have a six-groove right-hand rifling with a twist rate of 1:12 in (305 mm), designed to stabilize the lightweight 55-grain M193 projectile (standard at the time). However, after NWM had obtained a license to produce the Stoner 63A, some barrels were manufactured with a 1:8 (200 mm) in rifling pitch to be used with heavier experimental bullets. None of these were ever produced in significant numbers.

Features
 
A close-up of the receiver of the Stoner 63 Rifle variant. Note the perforated sheet metal guard that houses the rear sight.The hooked, non-reciprocating steel charging handle is typically mounted on the right side of the receiver. It has 24 lightening holes and engages a projection on the piston to draw the piston and bolt group to the rear (cocked) position. The handle should then be pushed back forward allowing a flat-spring latch riveted to the front end to capture a slotted plate welded to the front of the receiver. With the right-hand feed mechanism with underslung box carrier installed the handle is awkward to operate, so a special slotted forearm with a bottom cocking handle was developed.

The nucleus of the Stoner 63 system is the receiver which is a rectangular sheet metal pressing. The gas cylinder, support structures, brackets, lugs and other devices are welded in place. The front portion carries the piston and barrel and is perforated to reduce weight and improve air circulation around the barrel and gas cylinder. The rear segment holds the piston extension and bolt group. The ejection port is on the right side when the receiver is inverted and the weapon is configured as a rifle or carbine and on the left side when in the various machine gun roles. The various components are phosphate finished and then coated with a black baked enamel finish called Endurion. Early examples of the Stoner 63 were delivered with all wood furniture, however these were soon replaced with black polycarbonate parts with the exception of the handguard, which remained wood, but was painted black.

The Stoner 63 bipod is a non-locking type that attaches to the gas tube; it does not pivot and has a limited height adjustment feature but does not pivot. The Stoner 63A bipod is extensively perforated with lightening holes and can be locked in either the stowed or deployed positions. It too does not pivot but is compatible with the earlier Stoner 63, whereas the Stoner 63 bipod will not work with the later 63A pattern guns as the gas tube is of a larger diameter.

Ok, you now have a background on the Stoner..

The Stoner was built as a modular weapon system.  It could be a rifle, carbine, pistol, belt fed, sniper rifle, even an LMG.

it was a weapons system long before it's time.

That brings us to the question of how to build a modular weapons system.

BARRELS

A true modular weapon system would need to have replaceable barrels (maybe not quick change, but a system such as the AR).

The barrel would need to be standard much like the AR, with the ability to use light weight barrels as short as pistol barrels, to long bull barrels.

GAS SYSTEM

The Gas system would need to be totally adjustable.  From pistol calibers all the way to heavy calibers.  My thought is to have all the barrels use the same gas port hole size, and just regulate the gas system (maybe something as simple as carb needle valve system).  The gas system would also allow field striping for cleaning (wolf ammo is nasty, but how about building it so even black powder could be used if needed)

adjustable gas system automatically points to a gas piston system.  The system that seems to work very well is the FN49 long stroke, or even the VZ58 system.  The piston is easy to remove for replacement or cleaning, and there is no connection to the bolt needed.

BOLT

with this being a modular weapon system able to deal with many calibers, it's best if the bolt was one standard bolt (replaceble to change calibers).  an example would be a square bolt carrier, with a rotating bolt (such as the AR bolt). This could handle every needed caliber.  It could be a telescoping bolt carrier (think UZI) to retain mass for the bolt assy.

It would likely have two bolt carriers (pistol and rifle).

Recoil spring? designed based on the bushmaster ACR or a dual recoil spring setup much like a Cobray.  This is to eliminate the buffer tube on the AR, so a side folding stock can be used.

FCG

while the FCG needs to be standard, I suggest the AR due to availability (AK FCG may get more expensive now that fewer kits make it to the US, and the AR FCG are always of high quality)

Modular Mag Well

This system needs to have a replaceable magwell system so it can fit AR mags, AK mags, pistols mags, Uzi mags or any other mags needed.  or just a closed off mag well for single shot and belt fed designs.

Receiver

The receiver should be a standard receiver for all designs, so a standard bolt can be used.  it would seem a square tube receiver or a bolt together modular receiver could be designed.  this allows you to replace damaged parts, and mad future add-ons / changes to the system and still retain backward compatibility

Firing Pin

Recommend AR15

Grip

While there are a lot of cheap grips on the market, the most widely found would be the AR grip and it can be found in many styles

Stock

personally I like the newer ACR stock designs adjustable for length, as well as scopes, and they are side folders, but this system could be build with adapters in mind so you could mount a special purpose stock, AK stocks, AR stocks, no stock etc..

Forearm

No real design in mind.   just a free floating design with the ability to mount rails.  if it was designed to fit the AR, then you have hundreds of options for the look you like.

Sights:

Iron sights should just use BUIS for the AR, while Optics should be a rail mount system like all others on the market, but it could also mount an AK rail as a backup, so nearly any type of optic could be mounted.

The above is nothing but thinking out loud, and trying to design a weapons system that could be built from components without any major tooling.  you could chose you caliber, style of mag, and barrel length and it's possible to even have a bolt action design (rifle) or single shot (rifle, shotgun) from the same system.

The parts could be manufactured from several places, the receiver could be as simple as an 80%.

feel free to post your ideas on the weaponeer project...  and lets see if we can make it happen.

Pics of the Stoner

http://www.knightarmco.com/lmg.html

Mr Weaponeer,

I do like the FAL lower. Still cheap to get (Sarco) and 922r parts are available. You would then have various stocks (folding, wood, plastic) to choose from. Same thing with the FCG. Not hard to find, and if you changed your FAL out for 922, you probably have a stock set stashed away. I figure that you are 50%  of the way on the design, just by choosing the FAL lower. Now making it clip or belt fed... thats the tuffy!

I want this project to happen!

I was going to go this route using a purpose designed AK receiver flat (much thicker for the BELT FED option). You can also get cheap belt options (links) and a can... forgot who...

Anyway, you can custom design trunnions for various barrels/ stock attachments. Everyone probably still has their AK flat benders from the Golden Era of building.

my thinking (so far) is to use aluminum plates for the receiver.  aluminum works for the AR, it should work for a modular weapon system.

My thinking is a common rear trunion that would fit the FAL lower.

I would also like a common AR15 style front trunion (threaded for the AR barrel) with a hole for the gas piston.

Receiver at this point would be side and top, and bottom plates that would/could bolt to the trunions much like an AK build, but much thicker than the 1mm AK receiver.

waiting for other ideas before i can explorer the receiver ideas much further.

Weaponeer,

I was just watching youtube videos of automatic weapons fire. The MG 34 and 42 were very interesting to look at. The MG 34 looked "tubular" in the FCG back. Whereas the '42 had a nice easy barrel swap, it would appear.

I was also thinking about "plate" guns. We don't have to go as thick as a 1919, but with a few plates and angle iron, a unique gun could be created. Something like the Mag/ M240 line... Similar to what you were mentioning in your last post.

Hey, just throwing ideas... anyone else?

I think trying to use as many off the shelf parts as possible will really help the design.

The receiver would be easier if it was square, and it's not like it can get too think due to the FAL lower.

This is the point I wish I was good at CAD

guns1977 wrote: I like the idea of a quick change barrel, mag and belt feed option, so my thought are a ar barrel in 7.62x39 ad use rpd top cover, then flip it up to insert the mag? I don't know just thinking. It would be nice to have a SAW weapon

Personally I was thinking 6.5x39mm (should work in the RPD belt just fine), and the RPD top cover should work just fine.

The flip up top cover is interesting for a mag, but it would be better to just pull a pin to remove it so you could use a mag saw style.

lots of interesting ideas

now what if the top of the receiver was the same as the bottom?   You could flip the weapon upside down for belt fed operation, slide on the top cover, mount the BUIS on the other side (rails on top and bottom).  The gas tube could be on the bottom for belt fed, and top for mag fed.

basically you are turning the weapon upside down to refit the modular system. The replaceable mag well, could be replaced with a feed tray and top cover.

still leaves a lot of questions for such a design, but...  I still see it as being possible (on paper)

Didn't Stoner start creating the Stoner 86 Weapons System which was pretty much dropped after he retired from ARES???  I think it became the Ares Light Machinegun or and still is sometimes referred to as the Stoner 86...

IIRC, it was a next-generation version of the Stoner 63 - chambered in 5.56mm NATO, and likewise was a highly modular weapon!  I recall seeing it when I was a kid in the 1980's in a Weapons for Law Enforcement type magazine at the time...  They were expecting great things from this weapon - but due to piss-poor management inherent in ARES (remember the SHRIKE AR upper screw-up too?) the project was doomed from the beginning.  His cofounders at ARES were complete business management morons, unfortunately.  Otherwise we would've seen MANY more great ideas from his brilliant mind!

When he went to KAC in the early 90's he brought his Stoner 86 design which was refined & introduced as the KAC LMG...

There was similarly a great deal of modularity to allow it to function with magazines, belts, and utilized a wide variety of different configurations with options for mounting optics, IR & NVG options, and other accessories.

don't forget the XCR-L Modular Weapon System from robinson arms

and

http://www.robarm.com/M96_Home.htm

Guys...

I see some good ideas!

Why not use a MG42 or RPD top cover setup for the belt and the Slide configeration for the BAR to allow the insertion of a mag from the bottom, with a pull pin to remove the feed tray from the top. And a delayed ejection for a port further back @ 45 degrees.....