wanting to design a new pistol/pdw

[barnbwt]

If you don't have it, I think Quickload is probably a prerequisite for anyone designing cartridges from scratch. I've heard it's pretty darned accurate most times, and it's a lot cheaper/easier than making test barrels/cases

Well, there's a few ways to constrain (define) your solution here;
-Arbitrarily set a ballistic criteria to shoot for (max, min, and goal; momentum, velocity, energy, penetration, pressure, bolt thrust)
-Arbitrarily set a max overall length (by choosing a magazine, most likely)
-Arbitrarily set a capacity requirement (by modifying diameter)
-(or) Arbitrarily set a diameter (I'd choose something narrow enough the aspect ratio is still 'rifle like' and less prone to feeding jams. Double-feed mags are awesome-er to load, btw)

Between these, you should be able to define a range of possibilities for your case volume, and from there play with bullets/tapers to see if your ballistic criteria are possible. If so, it really doesn't matter what you tweak from there, since capacity + ballistics are about 98% of we have different cartridges for . The remaining theoretical reliability/efficiency variables will likely be set by what types of barrels, bullets, and brass are cheap/available.

I wouldn't worry about whether your design can be made strong enough; pretty much any type of locking breech can be made beefy enough for safe operation on a pistol as large are we're talking. I wouldn't look at cloning the C96 too closely, though; the design is incredibly inefficient, spatially. The bolt extends very far behind the bolt face before you even get to the lugs (mid-length lugs, really) and then the lugs/lock themselves are stacked atop the already-tall FCG area. No reason on earth the lugs couldn't be placed on the sides of the bolt body, nearer the front (more like a 92 if the locking piece is frame-mounted, VZ58-ish if the locking piece travels with the bolt. I'm positive it doesn't matter which, though I'd snap up a micro-VZ58 in a heartbeat

TCB

 

[justin22885]

i do agree with what others on here have been saying about using a pre-existing cartridge.. make a successful design around that first, but the only magazines that seem suitable are in fact the carbine mags for the longer cartridges.. but the more i learn about the 30 carbine itself and the 22 spitfire the more i like it

 

[barnbwt]

The fact Numrich has Spitfire barrels already is pretty interesting. I think I may actually look into it as an alternate chambering for the Skorparev, depending how well machining goes on the PPSH-mag prototype this weekend.

I'm also glad I've shown at least one other person that there really is a pretty glaring gap between pistol mags and rifle mags (considiring we have like 12 6.5mm rifle cartridges and even more 9mm pistol rounds; how the heck is the M1 Carbine the only mag available between 45ACP and 5.56 size? )

TCB

 

[justin22885]

well.. i still think we need a semi automatic that can chamber .221 fireball, which seems to go toe to toe with 5.56mm in the sub 14 inch barrels, at significantly less weight, and a shorter, lighter action.. it would be better in my opinion than the 5.56 itself in a carbine platform.. so imagine something the size of the P90 that had all the firepower and impact as a 12" AR-15?

seriously doubt a magazine to fire that cartridge would fit in the grip of a pistol.. but i think a bullpup could be really good for that cartridge, make it REALLY compact and lightweight.. however to this date this cartridge is only used in bolt actions and single shots..

so im going to start working on something based on this cartridge, a semi automatic in a very, very compact platform, probably use the steyr AUG system for guide rods and recoils spring, eliminating all spring behind the action allowing it to be REALLY short.. so, we can stick a flag in this project, its going to happen, and the magazines designed for it could work with 30 carbine, 22 spitfire, 5.7x28, 4.6x30, all of it

now.. not to get confusing.. lets set all that aside, the bullpup/carbine and the .221 fireball as one project.. unfortunately, i will have to design magazines for it but i will probably go with a double-stack box magazine

___

now for the pistol/pdw project which is really more on topic, the combo using the same cartridge ive been looking at ballistics for the .30 carbine and the 22 spitfire.. what ive learned is this.. 22 spitfire starts out with just a bit less muzzle energy, but at and beyond 100 yards, it has more muzzle energy than the 30 carbine.. after 300 yards though the 30 carbine has more (more momentum from its heavier bullet).. however the energy levels of either cartridge is so damn low at this point its not worth mentioning anything beyond 300

the other aspect of the ballistics besides energy that i was paying attention to is the drop and time of flight.. essentially the arc it makes, and as predicted the 30 carbine due to its much lower velocity has a considerably longer flight time and significantly more drop.. id say the winner in the sub-300 category most definitely goes to the 22 spitfire.. more power, higher velocity, flatter trajectory, and shorter flight time

ive also compared ballistics of smaller sub 34mm cartridges and from what ive gathered the 10mm seems to nearly match the 460 rowland and it far surpassed 9x23 winchester and 7.62x25

so for a pistol and a carbine, ive narrowed it down to .22 spitfire or 10mm.. and 10mm is already available in many handguns and pistol caliber carbines

so i think the pistol/pdw cartridge of choice is .22 MMJ spitfire.. now some people again may have problems with a longer grip in an automatic, but theres always an option of using a double action revolver as a duty/carry companion to the PDW for people with smaller hands (or those who like revolvers) since one of the three projects i have going on right now (my .308 caliber rifle, this pistol/pdw project being two of them) the third im working on is a top break 357 mag revolver.. ive always wanted an MP-412 but due to clinton era importation bans they never made it into the US.. so basing it on a webley mark IV, beefing up where necessary ive decides to design my own top break 357 mag revolver.. .22 mmj spitfire could EASILY be an alternative chambering for it

the way i have it envisioned is this.. picture an HK MP7.. just external similarities, i doubt i want mine to be gas operated.. maybe though?.. now imagine the MP7-esque PDW firing .22 spitfire or 30 carbine

 

[barnbwt]

"the way i have it envisioned is this.. picture an HK MP7.. just external similarities, i doubt i want mine to be gas operated.. maybe though?.. now imagine the MP7-esque PDW firing .22 spitfire or 30 carbine "

It'll be a big brother to the MP57 I'm working on! Very cool idea, I'm interested to know how you plan to work the magazine in since it's far too long for the current grip, obviously, and won't fit PS90 mags overhead. A helical mag would certainly fit over a compact action and hold a goodly number of rounds without raising the sight plane too much. FWIW, the falling block action concept I've come up with would easily fit in a large pistol, and if recoil instead of gas operated, would be fairly simple in practice. If interested, I can go into the details of the operation here.

TCB

 

[Jim Watson]

A bottleneck cartridge in a revolver has its own set of problems.
I don't think it a viable alternative for those of us with sub-Desert Eagle hands.

 

[Trent]

looking at the P90, its 5.7lbs, looking at the M1 carbine its 5.2lbs, 7.62x25 doesnt have as much penetration as would be needed.. i mean, it offers a lot, but nothing on the level of the 5.7x28..

...

ive also compared ballistics of smaller sub 34mm cartridges and from what ive gathered the 10mm seems to nearly match the 460 rowland and it far surpassed 9x23 winchester and 7.62x25

Your assumptions here need a little correction.

I would look again at the 7.62x25. Compared to the 5.7x28, it is capable of MUCH more penetration. It's pushing a bullet over 2x as heavy out at the same velocity from pistols. You don't need a degree in thermal dynamics or theoretical physics to understand that more mass = more penetration at a given velocity. Simply the law of inertia.

Compared to 10mm it might not hit *quite* as hard but it has a narrower cross section which would lead to deeper penetration, and (if you load your own) a pretty interesting selection of projectiles to use. It also has the ability to stay supersonic much further out than a 10mm, which is important for ballistics.

The *only* reason I haven't really invested myself in to a 7.62x25 platform is ... well, pretty much all of the rifle platforms are old, ugly, and pretty damn heavy for what you get (PPS43, etc). If a lightweight modern bullpup carbine with compact, high capacity mag were made in that cartridge I'd *seriously* consider it in lieu of a PS90 for home defense.

These guys do an SBR gas-operated M4 conversion for that caliber; http://www.cncgunsparts.com/

Which is intriguing but until Illinois gets the 26" minimum rifle length issue sorted out on SBR's, not of much use. (We can have SBR but the overall length must still be 26", due to the ATF not being able to decipher the word "OR" properly in our SBR law. They're insisting the law is re-written to properly exclude C&R holders from the 26" requirement, as the sponsors of the bill intended.... can't chop my PS90's or build a sub-12.5" AR-15 until it's sorted out next year...)

 

[barnbwt]

Yeah, I noticed that, too, but let it go because I assumed he meant armor penetration (not piercing), this being a PDW thing. 5.7 (or any small and fast round) will shear through stiff fibers and even plate more efficiently than larger caliber equivalents, but obviously the drag through dense material slows it down more quickly than a heavier projectile (as would shearing through a dense material like plate). Small & fast is great for getting through membranes (armor layers) that a large object would deflect or be arrested by, because they punch out a little piece of that material the size of the projectile tip. But the heavy rounds can push more mass aside, which is what is needed once the armor membrane is breached.

5.7 has excellent shearing properties upon impact, even with hollow points (penetrates sheet metal better than numbers should indicate), and still maintains very respectable penetrations figures (IIRC it's like 14" for the pistol, 10" for the long civilian rifle barrel) which completely ignores the fact said penetration is accompanied by fragmentation and multiple wound channels. I have to imagine a similar bullet accelerated at its pressure limit through a 16" barrel by the substantially higher gas volume of 22 Spitfire would be an incredibly nasty round; probably so much you wouldn't want to hunt with it. In fact, you may even have to go to tougher-jacketed bullets to get more than a few inches of penetration if your velocities get much higher (I've heard of hot-rodded PS90's only penetrating shallowly when the bullet shatters into birdshot upon glancing contact).

TCB

 

[justin22885]

what to do.. what to do.. the M1 carbine magazines may not fit in a grip, they dont look any longer than a five-seven mag, but they do look wider..

you could remove the magwell and grip, and just hold onto the magazine as a grip if the means in which it was locked to the rifle was secure enough.. but if it wiggled at all you could have feeding problems.. you could just not even use a detachable magazine, use the grip itself as a fixed box magazine...could go with a helical or p90 style magazine but these are very complex

could design a simple, thin sheet metal magazine, maybe on that only covers three sides of the ammunition that wouldnt take up more than a mm of space inside the magwell.. the magwell/grip itself could be thin carbon fiber

or we can just go with 7.62x25 or .22tcm if everyone thinks .30 carbine is that much larger than 5.7x28mm.. which ive read some fn five-seven owners claim .30 carbine actually fits in their magazines, though their mags are just a tad too thin for double stack

 

[justin22885]

check out the .22 gustafson carbine and 22 carbine in the middle.. i believe these are from a .30 carbine case too.. but use a more spire point bullet

 

[barnbwt]

How different is 22 Carbine from Spitfire (I got the impression it was a really common wildcat, so there may be numerous identical variants)? Gustafson looks like exactly the same thing (I'm a believer that the case gets the name, not the case+bullet ). The bullet ogives do look more like the 5.7x28, though, so the excellent Vmax 40gr would very likely work. Though I would also guess those aren't quite 224 bullets, right?

"you could remove the magwell and grip, and just hold onto the magazine as a grip"
Ouch...except;
"if the means in which it was locked to the rifle was secure enough.."
I would suggest making the magwell long but skinny by only having front/back straps to align the magwell; you said yourself width was the real issue with Carbine mags
"but if it wiggled at all you could have feeding problems.. you could just not even use a detachable magazine, use the grip itself as a fixed box magazine..."
Nah, we stopped doing that with the Steyr-Hahn machine pistols
"could go with a helical or p90 style magazine but these are very complex"
I know I'm repeating myself, so if you don't like the concept I'll drop it. But the mags, while difficult to visualize, are actually very simple in operation, and more importantly, in design/manufacture. The P90 version in particular is probably the easiest mag to redesign for a new cartridge there is; you'd just need a new 2" diameter plastic wheel with the new helical ramp and straight-feed feed lips in it, and a 3D SLA printer could easily whip up a functional prototype. The only easier mag design is the single-layer pancake type like the DP28 uses, but I doubt you want to go that route

A box mag may seem simple, but making a precision sheet-metal tube that follows the correct arc of your stacked rounds is incredibly expensive to develop (multiple rounds of dies to zero in on what you need, specifically)
Cool video on AK mags being made (Bosnia, I think)

TCB

 

[justin22885]

hmm.. i need to buy or make a replica of an m1 carbine magazine.. i want to feel how the magazine feels in my hand.. if it doesnt feel too bad in my hand i could make a really, really thin magwell out of thin sheet metal or carbon fiber that should only add an extra millimeter all around

and yeah, that .22 carbine is the same as the .22 mmj spitfire, but as you can see uses spire point bullets which seem to fit just fine.. i think it could make a really cool PDW cartridge.. so im going to get me a carbine mag now.. but ill probably just carve out a wooden block in the same shape or something

 

[justin22885]

well, found the blueprints for the M1 carbine magazine.. added a little more to the length and width of the M1 carbine and well.. i can actually handle the grip.. comfortably if i did in fact use a sheet metal or carbon fiber magwell/grip.. dimensions of the magwell/grip would be 2 inches by about .80 inches..

as i said though the grip this goes into will have to be folded sheet metal, welded along the seem.. you probably wont want to just hold onto metal for a grip so im thinking we could add a rubber grip-sleeve over top of this.. maybe even a grip sleeve with finger grooves

if you figure how narrow .30 carbine rounds are, and how really fat double stack .45acp pistols are.. the circumference of the grip for .30 carbine magazine shouldnt be any more than a double stack .45acp grip, say the .45acp glocks.. in fact, i just took measurements off a glock 17 frame and the grip of the glock 17 is roughly 2.13x1.8".. so a sheet metal magwell covered in a grip sleeve wouldnt be any bigger than a glock 17 grip.. as the glock frame is polymer it needs to be extra thick due to using a structurally weaker material to steel.. so i think the grip for an M1 carbine mag really can be made comfortable

so.. i think i will go with 22 mmj spitfire / 22 carbine with the magazine in the grip.. later on, 5.7x28, .30 carbine, and all .30 carbine derivatives would be options, but i will focus on the 22 mmj spitfire

 

[Havok7416]

Why not make a copy of an Automag III magazine? They can be had from Triple K for $52. I would send you mine, but... I only have the one! Holds 8 rounds by the way.

 

[justin22885]

well i think its important to get a double stack, and an M1 carbine mag is only slightly wider than the FN five-seven magazine because .30 carbine is only slightly wider than 5.7x28.. and if theres a way to get the M1 carbine magazines to work in the grip of a PDW, why not use it in the pistol as well?.. i think if i do anything else for magazines id just design more angled double stack magazines to shorten up the grip.. and since .30 carbine is pretty much straight walled the magazines wouldnt even have to be curved so the mag bodies could easily be made of folded sheet metal

 

[justin22885]

with all that out of the way ive been thinking about dimensions.. if we go something like an MP7.. it would be considered a pistol without a stock, or a SBR with it, i think a stock is important, at least a folding or telescoping stock and a 16 inch barrel could be added if someone didnt want to SBR it, so id like to design it as a very short barrel rifle

also, putting the magazine in the grip will reduce weight and bulk, only having one protrusion out the main body of the firearm, but if i kept the same overall length, but made it bullpup, i could double the barrel length which would make a huge difference in ballistics.. i could easily go with something about the size of a P90.. bullpup with an M1 carbine magazine in the bottom where the P90 ejects.. this would have a lot more power than something MP7 shaped

 

[barnbwt]

The MP57 posted above has a 16" barrel, and I think is like one or two inches over the min OAL with the stock out (it's an Airsoft shell that I'm using). Just an idea for scale. A reciprocating bolt design feeding from the grip would put the chamber right above the trigger guard, so your 16" barrel would stick another 4" or so out the end. I think SBR would definitely be the way to go

The P90 is certainly wide enough to accommodate a Carbine mag, I'd bet, and they also happen to be one of the cheapest Airsofts of decent quality (hint, hint; since making polymer stocks is probably even more insurmountable than magazine bodies, and the P90's is a really good layout). The P90 also has the dual-recoil rod/rail setup you'd mentioned earlier in your rifle thread, so...

TCB

 

[justin22885]

ive actually thought about using the P90 type magazine for mine, slightly widened for 30 carbine based rounds but thats a pretty complex magazine to redesign for something slightly larger.. im thinking of maybe making something that looked like a reverse kriss..

below is the kriss SMG.. imagine something like that.. but the magwell portion is behind the grip.. that space between the grip and the magazine could possibly be an ejection port, or the magwell could be moved to the front, and could eject behind it

another option if its made a bullpup is i could do something similar to the F2000's ejection, where it ejects into a chute, but that chute could lead out the bottom of the pistol grip.. cool thing about that is you could wrap a bag around the pistol grip and catch all your brass

im also thinging of having the barrel stop right at the trigger guard.. well, extend a bit more for a flash suppressor but im thinking it wont have a forward grip.. itll be held with both hands like a pistol, with one hand cupping the other

 

[barnbwt]

I'm a little confuse-ed by where you're going, now. The Super V is just about the polar opposite of a bullpup design

"im also thinging of having the barrel stop right at the trigger guard.. well, extend a bit more for a flash suppressor but im thinking it wont have a forward grip.. itll be held with both hands like a pistol, with one hand cupping the other"
You might want to confer with someone that owns a stocked pistol, first. I don't, but I can imagine the aiming/swing dynamics of a rifle without a foregrip would be quite different from where you use your weak hand to fine tune the trajectory. So much so that it might be off-putting (it's for sure better than a pistol-pistol, though).

You also pretty much force yourself into an SBR, since you'd either have a barrel stuck so far out ahead that the weight in front of the strong-hand support is annoying, or a stock so long that your trigger hand is where the foregrip would normally go (because there is still the 26" overall length requirement). Rifle ergos have closely evolved to match a bow's, and for good reason (we're adapted to it )

TCB

 

[justin22885]

well, im targeting the use of a 10" barrel minimum so itll be SBR anyway.. and of course a 16 inch barrel could always still be used.. ill have to look into that 26" requirement, if it still needs to abide by that because i know people who SBR their PS90s to the same length as the P90 have only about a 20 inch rifle

i did a search for some concept drawings of different ideas that give different shapes and layouts for a PDW/SMG.. some of the ones i like more ill post below.. just to give an idea what the PDW COULD look like

 

[barnbwt]

"well, im targeting the use of a 10" barrel minimum so itll be SBR anyway.. and of course a 16 inch barrel could always still be used.. ill have to look into that 26" requirement, if it still needs to abide by that because i know people who SBR their PS90s to the same length as the P90 have only about a 20 inch rifle"
Oh, I thought you only wanted SBR as an option (the rule is 16" barrel and 26" OAL for a non-SBR)

I think the "HC-9K" is the most plausible looking configuration; the KRISS bullpup looks like the apotheosis of poor balance, and the "Deadeye Defender" looks like a scaled up ZIP gun (love the ~2" telescoping stock, too ) with totally off ergos if you look closely (might be interesting with a more intelligent grip/selector/stock design, though, in a sort of bullpup schnellfeuer machine pistol role. I honestly have no clue whether the need for such a stocked pistol died out in the 20's, though)

TCB

 

[justin22885]

something like the HC-9K i could have forward ejection like on the F2000 that throws the shell down a channel that exits out the bottom of the pistol grip, cut the entire front end just after the front of the trigger guard.. could have a vertical pistol grip right there as an option, and then instead of having a telescoping buttstock on the backside of it.. you could basically just have what is essentially an adjustable butt-plate

im thinking a sheet metal upper, injection molded polymer lower.. if i designed my own magazine for the pistol i could make the same 20 round magazine fit flush with the PDW too with an optional extended 30 round mag

problem is an extended magazine may not fit.. would probably just be better to change the magazine angle to vertical and make it use the M1 carbine mags

another option is to use a casket magazine in the PDW.. could fit flush as you see it and is a quad-stack, so that flush fitting mag could be a 50 rounder or more

what about the one above the HC-9K?

 

[justin22885]

just real quick i went to that pimpmygun website and glued a bunch of pieces together into a rough shape.. this is what i came up with

 

[justin22885]

what? was it that ugly?

 

[barnbwt]

...huh?! What? How long was I out? Last I remember, I was scrolling down and saw this... --thump!


...


Oh, man, that was trip, I'm sorry. Didn't expect it to throw me for a loop a second time.


Just kidding; you wouldn't believe the difficulty I have in cultivating interest around here for crap that isn't already on store shelves . I've pretty much given up seeking advice on my Skorparev thingie, since the interest is so obviously lacking (whatever, I'm still building it, so it's no skin of my nose). My theory is A) most people are cynical about people actually building stuff in this country anymore B) most people don't really know enough to contribute much on such a technical subject, and C) most people just aren't that creative or willing to indulge creativity.

_____________________________________________
Back, to the subject at hand...(I did not react to the latest mockup because this thread was buried by new posts about identical 1911's before I saw it :banghead

If you can conceive of a means to extend that butt stock or butt pad out another six inches as an option, you may be on to something. I do worry about it being so tail heavy as to be worthless to shoot one-handed, but that's a pretty unimportant criteria, to be honest. The foregrip looks awful close to the trigger guard, too, so much that I'd just make the guard long enough to put a thumb through, or the gap between them great enough for the same.

I like the silhouette, though, it's like a sawn-off FS2000, almost . As it currently stands, the thing is so compact that I think trying to incorporate stuff like AR pistol/fore grips would be a mistake; those are all build for much larger guns, so it is incredibly like their angle/shape will be unsuited for a hold so close in your tongue could nearly reach the thumb-web of your shooting hand (looks like a ~3" gap between the two as pictured ).

In that case, I would take a page from the PS90 and copy it's grips, just with a much shorter back portion since your locked-breech won't require them. The nearly-round/circular grip shape of that gun allow your hands to rotate outward and upward as it is pulled close in . Your shooting grip is very nearly a thumb-hole already, what with the mag well. I think a PS90 shooting grip, and an MP7 folding/locking fore grip might work pretty well together.

One feature I think would be really cool on these little guns, would be an integral reflex sight that periscopes down to right over the bore axis. That way, you can have a very high and comfortable sight plane, but it will display a parallax-shifted image from ~2" down with dot/reticle, and with adjustable magnification or light amplification if you want to get real fancy . The trick would obviously be to build the sight into the frame design of the gun itself, early on.

TCB