wanting to design a new pistol/pdw

[barnbwt]

Here's a neat idea the gun-building community has been pining for someone to try for quite some time;


The Seburo Model "Blah-de-Blah-Blah nevah seen a real gun in mah life"

With a sane magazine design and extremely short action, something approaching this could be doable. Believe it or not, a falling block actually allows you to move the magazine all the way back as pictured

 

[justin22885]

would you really want the magazine that far back though?..it seems like it would be very easy to press the magazine itself against your body when shouldering it which could potentially lead to feeding problems or be uncomfortable

also, not a fan of that kink in the magazine.. thats likely to cause a number of problems itself.. instead why not have a constant radius of the magazine that would allow it to contact the same points without the kink?

part of the reason i like the concept of side magazines is you can position the feeding and thus the barrel really anywhere you like, and if you triggered it like the FG42 the same trigger setup could work no matter where the magazine was positioned and it beats out everything else when going prone, only downsides are its not so easily ambidextrous and longer, or heavier magazines (like drums) would put way too much weight on the side of the rifle

you also mentioned something important about the PDWs is that a pistol grip magazine would significantly reduce weight and improve balance vs bullpup and front mag rifles, i just cant imagine anything like i designed being fired one-handed, i dont even fire pistols one handed, i always have my off-hand cupping the bottom of my shooting hand

i guess the question at hand here is, do we want a machine pistol, or do we want a shortened rifle, and you know, looking at a 10 inch AR-15, taking a few inches off the end of the barrel to compensate for the location of the breech to get an idea of what a 10 inch MP7 would look like, i think it would still be plenty short but would also allow it to be lighter and more compact with the stock closed or folded.. in fact, i liken it to the same profile as an uzi would have, and could possibly even base the design on something as simple as a mac-10 or mac-11 upper/lower

___

as for your skorpion design, id be willing to discuss that too.. as most people seem to be uninterested in such things we could continue the discussion in a private message on here

 

[barnbwt]

As far as pistol/machine pistol, decide whether you want the thing held with one hand; that's my criteria. My R51, Hi Power, and S&W 357 can all be shot two handed, but they only have one place to grab, ergo are designed for a single hand.

As far as compact machine pistols, my favorite profile is the TP9 (I think the select fire is BT9, or something) based on the ol' Steyr TMP.

It's basically a beefed up PX4, and just large enough that stock is useful and 2 hand grip is practical. The smaller machine pistols like the Beretta 93 are just pistols with the pretense of a foregrip.

You mentioned that a grip magwell makes the gun more compact, but I would argue not necessarily so, so long as a foregrip is required in the design. If the mag can be used as the foregrip (or the magwell housing), the rear of the action can shift forward. Look at the VZ61 Skorpion receiver layout compared to the TP9;

Instead of putting a foregrip out ahead of the magwell, beneath a needlessly long barrel/shroud, they use the mag for the grip and position the pistol grip at the rear most point of the bolt's travel. Were it not for the telescoping bolt, the barrel would be like 2" long and is obviously too short to put a grip under. The bolt travel is the same regardless, so letting it hang over the rear is wasted length (provided you don't have to care about balance that much, which I submit you really don't with a two-handed, stocked carbine as short as we're talking)

TCB

 

[justin22885]

well, my concern is with getting as much barrel length and therefor power as we can in a shorter package.. if the back of the pdw/machine pistol hangs off behind the grip, you can just use a shorter telescoping stock.. look at both the pistols you just posted, look how long those stocks are, thats all space we could be using for added barrel length, more power, and better ballistics, dont you think?

 

[barnbwt]

You aren't familiar with the work of German A. Korobov by any chance, are you? He had number of radical bullpup designs that were up against the AK47 back in the day when the Soviets were into such things. This particular one used a falling block action which allowed the magazine to darn near function as the buttplate. The most effective means of getting barrel length is to use a non-reciprocating action (i.e. move the bolt laterally out of the way)

TCB

 

[justin22885]

yeah.. i mean, im not opposed to the falling block design if i had better illustrations of exactly how they functioned, not much info on them as most designs are either incredibly old, obscure, or were only prototypes.. the madsen is about the best i can find and even this requires some reciprocating, though the entire mechanism requires only a very short reciprocation and then cam grooves to operate each function

using the short recoil system ive wanted, with a madsen like design theoretically would work very well, upon flying backwards the block is cammed up or down exposing the ejection surface and the ejector on a pivot hits a block and chucks the spent casing out.. simple enough, doesnt seem like this system could work with any kind of gas operation though as it would appear the mechanism needs to reciprocate with the barrel.. seems it would be easy to make it eject in any number of directions you wanted

what im wondering is this.. could we eject the case into its own little pocket, then when the action closes and the block rises could it then chuck that brass into an extra tube possibly directly above or below the barrel?

also, there would have to be an easier means to take ammo from a box magazine.. feeding seems as if it would be the biggest hurdle.. but you know, i notice a huge advantage to the madsen system.. most semi automatics have serious problems with rimmed cartridges.. rimlock and what not.. by the way the madsen id designed with its magazine, cartridges coming straight off the top and not sliding out through the feed lips it looks like the madsen could efficiently and reliably shoot rimmed cartridges.. now if a PDW used a similar system it could comfortably fire .357 magnum

 

[barnbwt]

Well, apparently no one can explain how the Korobov works; the one you see was put together from parts in his prototyping shop decades after his death by a museum/university . Lots of threads out there trying to decipher it (like the Antikythera Mechanism, or something) with no conclusive answer; maybe there never was one. My theory is they put the mag in the wrong hole (almost all of Korobov's other designs have the mag connected to the end of the pistol grip) and made up the rest

The main principle behind the falling block autos (of which the Madsen is the only one) is to have the bolt carrier/piston drop the block clear of the lugs the same way it would tilt or rotate it in a reciprocating actions. The difference from then on is that the reciprocating bolt carrier is what extracts and loads the rounds, as opposed to the bolt body; different, but really not that crazy in concept.

In the Madsen, which is a recoil operated design, the barrel/breech-block unit is functionally the receiver (holds the breech together when locked) and the externally-fixed housing the whole mess rides in operates like a bolt carrier. For my MP57 design based somewhat on the Madsen, the barrel/breech-block unit are fixed, and a piston drives rails alongside the action which drop/lift the bolt, and extract/feed the 5.7x28 rounds. Instead of dropping rounds into a slot on the side of the bolt, thus guaranteeing an awkward, non-ambidextrous design, I spin the round 90degrees into two opposing 'hooks' which constrain its motion is it is fed into the chamber on the return stroke --thus the PS90 mag.

"but you know, i notice a huge advantage to the madsen system"
Huge advantages to the Madsen system. It was just so awkwardly executed that no one saw them before crap like the BREN took over*. Basically, the Madsen dispels with most (all?) cartridge cycling issues so long as a minimum level of energy is dumped in the system by the cartridge (same as all autos). And it does this in a far more compact package than even the AR Stoner bolt can pull off, since that action still has to double in length to operate when the bolt retracts. The Madsen merely doubles in height when the bolt drops

TCB

*Not knocking the BREN; by contrast it was an exceedingly elegant execution of a brutally simplistic and unrefined action concept

"as for your skorpion design, id be willing to discuss that too..."
Ergonomical Inquisitations Requesterated --admittedly not the most descriptive title, but I was only asking for advice on where to place a grip safety

 

[justin22885]

studying the madsen, i got this idea.. instead of chucking cartridges down a ramp, what if the cartridge got chucked into a cavity in the block when the bolt was raised for ejection, then when the block falls again, this cavity is aligned with a tube that chucks the spent cartridge into a tube... this tube travels straight forward just to the pistol grip where a hole in the bottom of the tube allows spent cases to fall straight out the pistol grip.. just need to figure out how to feed cartridges

another idea i had was a rotating block.. block rotates on an axis parallel to the bore, as it rotates out of the way, the opening for extraction and feeding opens up... once it closes the block rotates back into place.. another idea i had was to make this block reciprocate, holding the cartridge captive as it feeds and extracts so when the block rotates the spent casings can be thrown down an extra tube as it closes..with this idea, there would be two bolt faces, so one can hold the case being fed, the other holds the case being ejected

but to make this idea a fixed rotary bolt that didnt reciprocate, at least, not unless it reciprocates with the entire action (a gas piston could push on a cam surface to rotate the block in one direction to eject, and in the opposite direction to feed and close the action again.. spring on the gas piston would be used as the recoil spring)

 

[barnbwt]

Mauser MG213 concept autocannon;

That should get some wheels turning

The design you described, of a flip-flopping bolt (sorry, couldn't resist ) reminds me of some ancient black powder breech loaders whose name unfortunately escapes me (there was one on GB for the longest time, but I can't find it now). You flipped the bolt out of the action to the side, dropped in the powder/etc (I don't think it was a cartridge gun) flipped it closed, and I think the hammer or a separate lever locked it closed. had to have had more gas leakage than a flint-lock .

What you've described sounds pretty much exactly like a falling block, only it falls on just one side to expose the breech. I honestly can't say if there's an advantage or not to true falling block or a tilting block, but they all would seem to make for incredibly strong and short actions. The only downside I can see to a side-pivoting bolt with axis parallel to the bore is that your action won't be symmetrical (so possibly harder to machine and design for)

TCB

 

[leadcounsel]

As for what I'd personally like to see... I agree with the discussions above about the 762x25 as a potent round. I would love to see a compact rifle using that caliber. And it's small enough for a grip-mounted magazine (like the Beretta rifle). Maybe even design a bullpup... But frankly with the surplus all dried up, that ship sailed a few years ago. Now, with ammo costing competitive to actual rifle calibers, if you're going to design a bullpup you may as well use 556 or 762x39. And then you're squarely competing with the Tavor, Steyr, MSAR, Keltec, and the SKS aftermarket stocks, the AK aftermarket stocks, etc.

These CAD drawings look neat and all, but there are just so many current offerings that I just don't see these selling much. Sure, they look great on paper, but there is a lot of testing to be done and probably 5 years worth of trial and error before they are marketable reliable (you can't put out a terrible product and be subjected to internet bashing and recalls and expect to survive in todays market).


Consider this: I hate to pee on someones cheerios, but there are three or four ways this could really work out.

First, a design from flash to bang, licensing, manufacture, production, recalls, marketing and advertising, etc. will likely cost hundreds of thousands of dollars in capital.

If it flops, game over.

If it is a mediocre success, or is something of a Lorcin Jennings, etc. eh, it'll disappear into obscurity.

And if it's a wild success, in today's extremely thin margins and highly competitive gun production world, it will immediately be copied and improved by a few competitors with deep pockets, and already with machining, infrastructure, and supply chains and brand names in place. If that is your only product, you could quickly lose your industry market share.

Think Glock... had he not made such huge inroads, and competitors slow to copy, he likely would have failed. He was fortunate that it took a decade for the competition to react and copy. Keltec lost huge market share to Ruger on their pocket pistols. There are many examples how innovation is quickly copied and R&D costs are eaten by the original producer.

The last, and perhaps most lucrative, would be to design and produce a working prototype and patent it and sell it to the highest bidder...

As for designing a new caliber, the last thing we need is yet another caliber that is marginally different than the current offerings. There's probably dozens of dead calibers for every one in common usage.