designing a rifle and would like some input

In simple terms, a people's rifle should be able to be assembled by nearly anyone. The AK sure can't, and basing the design on the AR features would be a major improvement. That is because it's modular and meant to be assembled without any presses or special tooling.

I would certainly use the AR barrel extension and bolt, precisely because it doesn't require pressing it into a receiver and simultaneously setting headspace. The barrel extension on the AR screws on, and with a micrometer like adjustment, the headspace is set and then the extension friction pinned in place. It's NOT gunsmith level work and that is the beauty of it on the assembly line.

On the other hand, when Armalite designed the AR10 and M16, it was meant to showcase some advanced methods, and the forged aluminum receiver was the result. It's appropriate for mass production in an advanced technology environment, and does reduce weight and cost in high volumes, but the upfront costs are also high. In extremely low production or low cost manufacture, a folded sheet metal lower and even upper would be much more appropriate. The 1" ID upper could definitely be fabricated from tubing. The makers of monolithic uppers are even using extrusions, not forging, to reduce the costs even more.

I speculate that someone could go into business successfully selling an upper and lower that aren't forged but do take all the AR parts. And a simplified version build to look like a traditional manual action with wood stock wouldn't be out of place. A left side straight pull "bolt action" would be the result.

The M16 has influence a lot of battle rifle designs in the last 50 years, mostly because of the controls and barrel extension concept that are widely copied. They work, in the SCAR or BLR. Sounds like a good project to adopt them, because the extremely simple construction and lack of involved assembly are the key points to a people's rifle. With the combined cartridges available in barrel and bolts for the AR10 and AR15, there's over one hundred to fit nearly any taste. That alone should make it the preferred choice for parts.

justin22885 said:

a trunnion designed to attach an AR-15 buffer tube and any AR style stock

Click to expand...

Not sure if you are intending to use the buffer tube as a receiver extension like in an AR or not, but my vote is not. Keep the bolt out of the stock so the gun can be fired with the stock folded.

As far as the lockup system, something like the AR or AK has a big advantage over a traditional bolt gun that locks the bolt to the receiver. The AR's barrel extension and the AK's front trunnion both keep the forces and complex machining to a small part that can then be attached to a more easily made and less strong receiver. The advantage is in making sure the serialized part has as few difficult machining operations as possible. I've honestly wondered how long before we see a bolt action with a barrel extension design...

Have you looked at the AR-180?

Just make sure you don't accidentally recreate an ar-180. I think their lower was all stamped.

Sounds fairly similar to the Leader T2; which is basically a simplified AR18.

http://www.forgottenweapons.com/rifles/australian-automatic-arms-sac/

If you want it to be produced in a small machine shop, you definitely do not want to the an AR-type many-lug bolt. That is not a simple thing to fabricate.

You should make it so +80% of the weapon can be printed on a home model 3D printer, and all you would need to do is buy a factory barrel, magazine, and get something at the hardware store for a bolt and mainspring.

The reciever, trigger group parts, and furniture could be plastic.

Heck, if the LuLz Liberator can fire a 380 with plastic barrel, then any rimfire or shot shell cartridge would be an option.

I assume this is designed to be open source so anybody who wants to can pay a few bucks for plans and build away? If so I may play along.

As I'm sure you know by now, there's advantages and disadvantages to the different bolt types. The bolt concept you showed, while simple to produce, has tapered lugs that have less surface area for a given diameter than a square of the same profile (like the Stoner bolt), so while probably simpler for a guy with a mill to carve up, it will need to be bigger/heavier than absolutely needed.

The advantage of a rotating bolt over a tilting bolt (or locking piece) is twofold; first, the bolt can be incredibly short --theoretically the length of the lugs-- and second, the bolt face does not move relative to the cartridge, since both are co-axial. The obvious disadvantage of a rotating bolt is that the trunnions/extensions and bolt heads are very difficult to machine. Yes, you can use off the shelf AR parts for the hard stuff, but by that logic you will invariably end up building an AR clone; parts commonality for the sake of parts commonality leads to you designing new platform for the sake of a new platform. A truly better/different design will be fairly incompatible, and that is unavoidable.


The advantage of a tilting locking piece, and more so, a tilting bolt, is that the bolt is extremely easy to machine, as is the receiver. However, unless you are attempting a tilting-bolt design that tilts at the front, its locking lugs will be further back, requiring more of the receiver to be built to carry immense bolt thrust. And if you tilt the front of the bolt, you will find it extremely difficult to design get enough lug engagement without a ton of bolt motion relative to the case head, which makes extraction and feeding much more complicated. One benefit to the tilt bolt that the rotating will never achieve, is the ability for an open breach; the VZ58 exposes nearly half the action (and the magwell nearly the entire other half) when the bolt carrier is retracted; something an AR can only dream of --just try fishing a jammed primer or other debris that makes its way into the barrel extension out by hand, but on the VZ an index finger can quickly and easily brush out the locking rails and you can visually glimpse right into the chamber. Tilt bolt actions with exposed bolt carriers like the VZ/SKS are also much more easily convertible to belt-feed (UK59 is a belt fed VZ58). The benefit of separate locking piece designs is they move the lugs forward, allowing more of the gun to be flimsy and lightweight, but at the cost of added complication and expense.


(staring straight down through the VZ58 locking lugs, magwell, and breach)

Another action variety you may not have thought about is the Degtyarov, or locking flap. You have a central bolt body that is simply reciprocating into the chamber to feed rounds, with two locking flaps on either side that are pushed outward into recesses by the bolt carrier. The open-bolt designs (not legal in the US) are stupid-simple, but even a striker/hammer fired closed bolt is very simple to visualize, and there is no easier receiver to make by hand; it's basically a tube with two notches cut in the sides. These are also by far the easiest to convert to belt feed (hence why the DP28/DPM had a belt conversion, and all subsequent variants like the RPD and DShK were belt fed). The "Skorparev" compact carbine design I am working on is a miniature DP28 in 7.62x25, and has a receiver built from telescoped steel tubes brazed together and extremely simple bolt pieces (nearly two-dimensional machine parts). I differed from the true rear-locking Degtyarov designs by putting the locking lugs up front (first attachment), which makes the beefy part of the receiver shorter, but also makes the flaps more complex; the DP28 flaps are 1/8" thick rectangular plates with a rounded end --hard to get simpler than that.

RPD, DP28, and DShK bolts, all in a row (the Degtyarov Trifecta )

And, my Skorparev concept. The idea here was as small/light a legal-length straight stock rifle as possible, cheap and easy to make, that is gas operated, uses PPSH drums/mags, and is automatically ambidextrous (has auto-switching ejection based on user hand position)

Another design I am almost positive you have not considered, is the falling block. If you think about it, a falling block is basically a front-tilting bolt with a really long swing radius. Not very many semi-autos have exploited this concept, but the Madsen LMG was/is a very dependable if awkward looking design. I am pursuing this design for my MP57 project in 5.7x28, since the tilting bolt requires very little momentum to operate, making it in my mind perfect for super small magnum cartridges. Falling blocks are the linear analogue to the rotating bolt, and they posses all the same benefits such as extremely efficient load transfer and extremely compact size. One huge benefit over all reciprocating bolt designs is there is no reciprocation along the barrel axis, so the overall length of the action is equal to the cartridge. The lone detraction is a big one; they require the entire bolt face to scrape over the chambered case head, and a separate mechanism to extract/feed the new round. This is very foreign to folks who are all used to reciprocating bolts doing this work, but the job of feeding/extracting falls to the bolt carrier in the case of a repeating falling block. But check out the second attachment to see just how easy the 'barrel extension' is to make. For my rifle, the extension is milled into the barrel blank itself before chambering, and is the only structural part in the whole gun --the rest is low stress stuff, just like in an AR. But see how much more compact it is (the dark grey square on the end of the 16" barrel is the entire receiver, and contains everything; a small tappet piston out front of the chamber powers everything)


And here's the Madsen LMG. You think a Broomhandle Mauser has weird internals, this thing is like nothing ever seen before or after, and ran like a top up against contemporaries like the Browning BAR . Still in use in Rio, I hear. Ian (forgottenweapons.com) has an excellent video and discussion of the operation and internals, as well as a comically-badass run and gun session
Incomprehensible operation and machine work, brilliantly simple magazines --too bad they are in a terrible place, which is why I opted to figure out a why to use PS90 mags for the MP57 design.

TCB

Sorry for the humungulungus post replete with mesmerizing animations. Gun design is just one of those things I get really excited about when I see people with know-how getting involved. Disclaimer: If you don't have a real good understanding already, be sure to bone up on the assorted NFA/GCA/local gun building laws, as well as an understanding of ATF regulations/recommendations regarding your particular design. Seek out the info before building it and posting the proof on Youtube (Disclaimer over)

TCB

It's totally backwards thinking to the rest of this thread but I would love to see another browning recoiling barrel. Make that happen in a pistol cal carbine and it would be an old school new school combo that would be neat. With modern steel it should be able to be downsized to take the smaller rounds easily. The length of travel would be dependent upon springs and recoil so it should be easy to build long to take everything from .380 to 10mm build it longer and heavier and you have rifle caliber capability. Make your reciever 4 ft long and you can handle 338 lapua and 50bmg...maybehttp://firearmshistory.blogspot.com/2010/09/actions-recoil-action-long-recoil.html?m=1

Out of curiosity, are you looking long term at bull pup or standard configuration?

And are you side, top, bottom, forward ejecting?

That Madsen is recoil operated, and shot 8mm, so the concept of a recoil-op rifle is very sound (the MG42 was, too). The problem with pistol cal rifles is the barrel is so heavy that the recoil won't budge it. Not to mention a tilt-barrel like you almost always see is a total no go. So, you're stuck with straight-recoiling designs which require the receiver to ride the whole length of the barrel (heavy, $$$). One possible option is the Pedersen hesitation lock, which manages an essentially recoil-operated action along with a fixed barrel (it's a hybrid of blowback and recoil-op) but I wouldn't want to be the small businessman trying to market this following Remington's act on the R51 (or the Model 51, either, since that was a tough act to follow )

TCB

justin22885
Do you have any knowledge or schooling in firearms grade steel selection and heat treatment?

That's going to be a dangerous hurdle for you to jump if you don't!

rc

"as to the falling block.. no, i didnt even consider that.. its a very interesting LMG.. unfortunately the footprint on it is huge"

You may want to take a closer look. The Madsen is huge because it's recoil operated, and the barrel/breechlock have to slide around inside a sturdy housing. Compared to a BREN (a comparable LMG with similar mag placement) the action is very stubby. The actual breechlock is no longer than an 8mm cartridge, and you would be operating it via piston or gas pressure that adds no additional length as opposed to letting it slide around. It is actually the shortest you can make a firearm action without a moving barrel (blow forward is shortest).

Here's a snubbie in use by Rio police:


"Do you have any knowledge or schooling in firearms grade steel selection and heat treatment?"
Use 4130-type carbon steels and you can hardly go wrong. Just design with a healthy safety factor, avoid super-hardened steels, and test carefully and incrementally, and it's pretty much impossible to blow yourself up. As I recall, the BREN receiver was straight mild steel, and it was a rear-locking arrangement, too . Just add enough metal and you're covered. The Skorparev is designed to withstand 90,000psi ultimate loads, 60,000psi proof loads, and 40,000psi operating loads, which is more than enough margin to cover my butt

TCB

I wouldn't put too much faith in FEM, even if it does generate pretty pictures; at the end of the day, the model is still based upon your assumptions so you must remain skeptical (it is pretty cool, though )

"wouldnt mind the ability to make the rifle adaptable in terms of its configuration"

One modularity idea I had that seemed worth someone else's time was to split the mag well; think of an AR upper/lower, only the front half of the magwell is integral to the upper. This would allow an upper change to alter the length of the magwell, resulting in a far greater variety of cartridges that could be quickly swapped in. Taken further, the Degtyarov bolts are obviously very scalable, so quickly designing them for a multitude of cartridge lengths and case heads would be a snap. You'd be limited only by how fat a single-stack magazine you could fit in the magwell (or you could use the magwell itself as an internal magazine for the biggest stuff, with feed rails integral to the upper)

TCB