Race to the Bottom... Long Range Pistol/Carbine Cartridge

Varminterror said:

.2” shorter but .1” fatter than 6mm ARC, so we can estimate easily from there.

Fudging numbers with outside dimensions, and roughly averaging the taper of both:

*assuming up front the shoulder volume difference is roughly negligible to keep the math simple - but we can come back to that later, since it’s easy enough to figure the volumes of the cones.

The 6 AE would have an annular ring outside of the 6 ARC which is .1” thick, but .2” shorter than the ARC sidewall, which is .92” long. So we have .92 * π * [(.535/2)^2 - (.435/2)^2)] = 0.07 cubic inches.

The 6 ARC has a longer body which would stand tall over the 6 AE, taller shoulder height, so we can simplify that also as the volume of the disc which would be the extra body length, so we have 0.2*π*(.435/2)^2 = 0.03 cubic inches

0.07in3 annulus minus 0.03in3 disc = 0.04in3 left over for the AE case, meaning it should have ~10grn H2O more capacity than 6 ARC, which is about 35grn H2O - and considering the 50AE is ~50grn H2O, I'd think we're probably somewhere in the right ballpark to expect 42-45grn H2O from the 6AE, so ~28% capacity increase, getting about on par with 6BRA...

But...

50AE is only running 36kpsi, with the 6 ARC running 52kpsi, 45% increase in pressure, so we really can't pretend capacity is the only relevant performance measure - for example, placing it beside the 55kpsi 223/5.56 or the 65kpsi 243wssm. Cycling back - this would be very similar in case capacity, ever so slightly larger, than my 357/44 B&D - just shooting a lighter bullet, and near the same pressure. Comparatively, 7-30 waters would have slightly MORE capacity than 6AE and shoots bullets of more similar weight and diameter, and has a max pressure of 40kpsi, which is getting within spitting distance on capacity, caliber, and MAP - 7-30 waters can get a 110 up to ~2600fps from a 14" barrel and offers about 25fps/inch of barrel, so a 16" would be about 2650. Scale that for pressure, and you might get a 110 up to 2500fps with the 6AE, or might get the 80grn stubby bullet you've described up to 2600-2650. Which isn't terribly far from what a 223/5.56 gets with 77-80grn bullets, which have a .22SD and a .45G1BC...

The bad news, of course, you're talking about a bullet with a .19SD and ~.15-.2G1 BC, slightly better than a bowling ball, while the 108's standard to the 6 ARC are running .26SD and .525G1 BC... A .2G1 leaving the station at 2600fps is transonic by 325yrds and sub-sonic by 400... Basically, it's equivalent to the 380 auto at the muzzle (bullet weight and speed) by 400yrds, out of a 16" barrel... Almost identical velocity at 300-400 yards to my 357/44 B&D out of a 7.5" revolver, using MORE case capacity at the same pressure, but I'm punching a 180grn bullet out there, instead of an 80, and I leave the station at only 1900fps - from less than half of the barrel length... I'll have more drop, certainly, 6.8mils instead of only 4mils, but 357/44 at 400yrds is going to hit like a 357mag at the muzzle, from a 7.5" belt gun, while the 6AE will hit like a 380acp at the muzzle, from a 16" carbine... Changing gears to look at the 223/5.56 with an 80grn bullet, a 16" tube will get up around 2500fps with an 80grn bullet, staving off transonic boundary past 600yrds, and not falling sub-sonic until 850yrds - where it TOO would have similar bullet weight and velocity as 380acp at the muzzle, but would have a .23SD, rather than a .19 (aka, far better penetration). Another example - I have a 15" 6 creedmoor, and I push 105 Hybrids at 2650fps - a 2.8" COAL, 62kpsi, and 52.5grn H2O case capacity... That would likely put an 80grn bullet right around 2950-3000fps - using 42grn powder in a 1.9" case at 62kpsi, and 2.8-2.9" COAL... Lots of guys run 6mm BR specialty pistols, 1.55" and ~2.2-2.3" COAL, which would be very similar in capacity to what you're describing in 6AE, but again higher pressure by +72% and not seating bullets down into the powder column...

That small bore capacity and low operating pressure is a problem. It takes a lot of barrel to get anything done with a small bore at low pressure, so something like the 6AE is a cute novelty, and guys like me do enjoy cute novelties, but it doesn't really shift any paradigms for performance.

I think the ballistics you described a few posts ago made a critical mistake. You mentioned getting an 80grn bullet to 715yrds super-sonic, but didn't really explicate how you can 1) get it to 2790fps out of such small cases, and 2) how you expect to get such a high BC out of a bullet with only .4" of tip length you have available in the 6AE. The 80grn Berger Match Varmint Flat Base has a nose length of .567", over an 1/8" too long for the 6AE's specs, and only carries a .3G1. In fact, Berger doesn't make a 6mm bullet with a nose length shorter than .5". The Speer 75grn Varmint Hollow Point might have an ogive short enough, but it's a .23G1, and I think that will even be HIGH for what is possible with a 6mm and .4" tip length. But I think 1) getting a 6AE up to 2700+ with 80's will be tough, and 2) finding 80's with short enough ogives to get to 1.685" which have a BC better than a bowling ball will be tough too.

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Varminterror said:

I spelled out on Page 3 the limitations of firearm design. We examined the Keltec 22mag which is a low pressure round and a straight blowback. Then all of the 5.7x28 cartridge firearms are DELAYED blowback with dynamic barrel mounting - and have relatively short pressure cycles, achieving only slightly more than 22mag… We looked at the Desert Eagle pistol design there too - a gas operated design, again, tolerating only 36kpsi at the energy level we’re describing.

So yeah, as I said on page 3, someone CAN design and build a gas operated PDW to sustain the pressure you’d need, but it’s going to be a new rifle design, with all of the complexity of design and inherent weight of adding the gas operating system. I’d venture you could prototype something for around $50k if you wanted, assuming you’re just asking for custom machined components and can do all of the detailed parts specification and design work yourself, unless you can machine the components yourself, which then offsets that same cost as lost opportunity towards profitable work - and you better figure out mags PDQ, which likely means you need to use Desert Eagle mags, because designing/manufacturing new mags adds massive expense really quickly.

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Varminterror said:

When you’re talking about a custom wildcatted cartridge in a boutique designed and built firearm which doesn’t yet exist at all, in whole or in part, I’ll contest that it’s far more “fair” to talk about using a standard 1:7” or 1:7.5” twist 5.56. I can buy factory rifles RIGHT NOW with appropriate design to spin the 80’s, what grip-borne mag fed carbine exists RIGHT NOW to swallow a 6AE? We have 4 pages here describing why it doesn’t exist already.

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Varminterror said:

I think it’s pretty obvious that this isn’t true. While we’ve moved the goalpost a bit during the course of this thread, effectively, you’ve adopted desire to achieve the performance of the 6 ARC, BR, PPC, but within the confines of a shorter cartridge, remaining intent upon utilizing grip borne magazines.

There is obvious market demand for low recoil, high performance, mini-length cartridges. The 6 ARC, as an example, was released during the height of covid, and still has quickly achieved ranking among the most popular AR-15 cartridges in the market, and has done better than any other Mini-length cartridge in bridging the divide into bolt action rifles.

So there is obvious interest in the performance standard you’re describing - there’s just a lot wrong with trying to achieve it in a short barrel with bullets with abysmal BC’s, and trying to wedging into a 1.6” coal. This extremely short length brings ALL of the complication to the table. When we were talking handguns earlier in the thread, not the compact PDW you’re discussing now, you implied, intentionally or otherwise, a maximum weight and size target, which the required gas operated design simply wouldn’t be able to achieve, and adding pressure via technology like the three part cases of the Sig Fury wouldn’t solve that issue, it would only exacerbate it.

So there is obvious interest in the performance standard you’re discussing, but there isn’t mechanical ability to deliver that from a “handgun action,” meaning size and weight, and there isn’t relevant market interest in PDW size and weight carbines which simply move the mag into the grip. That’s the juice which doesn’t seem worth the extreme squeeze it takes to get it.

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Varminterror said:

This isn’t true either. It sounds great, but it really, really isn’t true. We’ve made exceptionally little advancement in the last century of firearms design development. We know the designs, we know the materials, we know the chemistry.

...

You’re circling the flame - it’s close to reality, and guys have been doing almost what you describe for a long, long time, it’s just that reality often doesn’t usually live up to the excitement of the fiction.

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Varminterror said:

What you’ve exploded about in your last really is a pile of independent and unrelated arguments - and if you suddenly feel as though you’re arguing, that’s unfortunate.

But this, independently, is an example of inappropriate evidence to support your claim.

The 30 super carry is a new cartridge, not a new technology. The Shield Plus was a new model, but also isn’t new technology.

We’ve integrated new materials into firearms designs - aluminum receivers, carpenter steel cylinders, polymer grip frames, etc, but we really haven’t seen technological evolutions for a long, long time. We covered this recently (some of which was deleted, unfortunately) in another thread, as there simply aren’t many true gun designers in the world, and among them, typically their work truly isn’t “new design,” but rather modifications of the existing.

The Thiel quote above is absolute nonsense, and it’s plain to agree that it does not take a 10x product improvement to garner competitive advantage. I’m not exactly sure the relevance of posting that quote, and frankly, it’s pretty obvious that his career has not been built on products which did anything 10x better than the incumbent competition - but also obvious that an options trader turned VC manager would use such colorful exaggerations to describe the reason they profit so much from the work of those underlying their investments.

So again, all of these incremental modifications to old designs aren’t doing what your quote there would suggest - we haven’t really figured out how to make anything new, we’ve just figured out how to make things better, and more commonly, how to better make things. It’s through the refinement process like this thread which new products evolve - which is how I have spent my professional career.

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Varminterror said:

We’ve made exceptionally little advancement in the last century of firearms design development. We know the designs, we know the materials, we know the chemistry.

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Varminterror said:

The premise in the last page of this thread isn’t the same as the last, and there seems to be some bouncing back and forth (you state performance as a target which meets that of the 6 ARC, but then state that isn’t the target when challenged as to why achieving that target isn’t a free lunch - can’t really have it both ways). In this business of product development; we call what you’ve done here as “scope creep,” which isn’t always bad, but it’s never actually good. You started with interest in a long range capable handgun cartridge, then shifted to a PDW type carbine cartridge, with the only consistent parameters of design remaining the grip borne magazine feature.

I’ve attempted to provide information, and frankly, attempted to educate you on how to better self-analyze these design ideas for yourself. There hasn’t been any earth shattering science or mathematics described here, and there hasn’t been any insurmountable hurdle identified. Through this process, we’ve identified a path to achieve the performance standards you’re seeking, and we’ve identified potential case design and potential firearms designs to achieve it. No, it’s not going to fit into a 25oz belt gun like an FN Five-Seven, we just have to acknowledge it’s going to be stuck in something more like a 4lb Desert Eagle. No, it’s not really going to work with a 6AE, since the case is still too long for any 6mm bullet with a decent ballistic coefficient to still fit into a 1.6” COAL - but we know how to achieve the needed case capacity or achieve the necessary pressure to get the performance out of a shorter case. We did have to power through some naive ideas - like thinking a 6mm bullet with a .4” nose length would have a BC high enough to get out to 700yrds super sonic, and the idea that itty bitty cases at high pressure are relevant examples for increasing power factor and bolt thrust in larger cases without acknowledging the firearm design has to change (doing so again in this last post, mentioning the weakling of 30 super carry in a conventional pistol as evidence a 62kpsi+ cartridge should work with a magnum or Gibbs bolt face, rather than acknowledging existing firearms designs can’t do what you’re stating, and rather than acknowledging the firearms designs being used to do what you’re describing). But we’re largely arrived at suitable design factors - 40-50grn H2O capacity, case length less than 1.0”, 6mm, gas operated, and bob’s your uncle, you have an answer to the question.

But like the Shield Plus, Carpenter steel revolver cylinders, red dot sights, aluminum receivers, and polymer grip frames, the actual invention of the pistol and PDW you’ve devised here is a minor incremental shift on known technologies. Not earth shattering developments. Our world has been designing cartridges and firearms for a long, long time. There’s never really anything new under the Sun.

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Varminterror said:

I'm not sure why there's hostility here, but I can say, confrontation isn't my intention. At the core of our discussion, we've achieved your goals, but it seems you're angry enough about how I helped you solve your riddle that you don't see that we've solved it.

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Varminterror said:

My personal interest in this thread is driven by the fact this is the kind of pistol/carbine performance I've been interested in buying for more than 20yrs, hence my interest in doing the math and research I've done here to formulate this idea. And that interest, and the money spent seeking this kind of performance for many years, is why I know the limitations of existing designs to achieve our goals. I've spent hours on hours exploring this class of cartridges over the last ~25yrs, and have spent tens of thousands of dollars chasing this kind of performance in different cartridges and different firearms, even wildcatting some myself (as mentioned in my first). And I wasn't the first guy exploring this territory, guys have been looking for this kind of performance in "cross-over" cartridges for a long, long time - we can go back over a hundred years and find examples which show interest in this direction.

I'll also admit - it was probably 10yrs ago that I conceded to the fact that bigger bores tend to do much better in these types of firearms when they actually need to kill something on the other end. I really wanted something in 30cal when I started down this road years ago, but acknowledged after a 300 whisper pistol, the performance downrange wasn't so whippy. I even played with a 300wsm pistol - which simply is too much for what we're considering here, and even my current 6 creed pistol is more than we're seeking. BUT... those experiences and the research leading to them is what makes it easy for me to interpolate where this particular cartridge/firearm design will land. We're not mapping uncharted waters here - we're operating between known points in space. Folks have sailed past this particular island many, many times - but what is seen on the beach from the water is an empty island with rocky shores, so not many folks have anchored to attempt the beach, despite well mapping the island's position in the ocean.

I'm not certain how it has been missed, since I've pointed to it a few times in this thread, but we HAVE several 50kpsi pistol designs on the market today. But also pointed out a few times in this thread, is that none of those are short recoil or blowback actions, at least not for any cartridge of anything near the performance standard we're evaluating in this thread.

In other words, you're not buying something which looks like, or at least functions like a 1911 or Glock 19 which will deliver what you're seeking. There are those oddballs like the Automag and the Super Carry which are higher pressure, small capacity, straightwall cartridges, but they still don't come even remotely close to the performance level we're evaluating in this thread.

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Varminterror said:

Bolt thrust of a 50kpsi 9win mag is 6100lbsf, whereas the larger magnum diameter you’re discussing at 62kpsi is 14,500lbsf.

14.5k is considerably more than 6.1k, yes? That’s a problem for short recoil operated actions.

I’m not sure the Automag is the best example of properly designed operating system, how’s it doing today in market?

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Varminterror said:

So what you find in handguns chambered in high pressure, high performance cartridges are things like Desert Eagles, AR-15 pistols, AK pistols, bolt action specialty pistols, break actions, etc - big gas operated or manually operated actions commonly described as "rifle actions with short barrels and no stocks." Why? Because, as I've mentioned several times here, when we push bolt thrust, pressure, and overall power above a certain threshold, we can no longer use conventional short recoil or blowback actions. I've specifically cited the Desert Eagle as a gas operated action and ANY 5.7x28 pistol as a delayed blowback with dynamic barrel designs, pointing out that these are designed and built in these ways not because someone WANTED a Desert Eagle to weigh 4lbs, but rather that it NEEDS to weigh that much to withstand the power of these cartridges. The FN Five-Seven and the Ruger 5.7 aren't designed as delayed blowback with dynamic barrel mounting because someone wanted to build complicated pistols, but because they NEED that design modification to withstand the power level of the 5.7x28mm cartridge - again, which is below the performance standard we're considering...

So again, the only attribute missing from known and manufactured products compared to what you've proposed is the specific combination of grip-borne magazine with this level of performance - which is easy enough to design both in cartridge dimensions and firearm design.

We DO do it. We have AR-15 pistols, we have the gas operated Desert Eagle, we have Rugers using Carpenter Steel cylinders with smaller cylinders than corresponding S&W's to sustain 65kpsi without the mass of the X-frame, we have things like the proprietary WSM and WSSM AR-15 and AR-10 bolts and barrel extensions, or the 30RAR with its proprietary metallurgy in barrel extension...

We don't do specifically what you're asking for all of the challenges I have mentioned here - to get a 1.6" COAL with a 6mm cartridge which contends with 5.56 for downrange performance, we have to design a cartridge which looks more like a hockey puck than a rifle cartridge, and we are forced to use action designs which add size and mass to the firearm, so we end up with something a little less like an FN Five-Seven and more like an AR-15.

Your contention here kinda feels like you're wanting a Porsche Boxter to pull a semi-trailer. We know how to make the horsepower, we know how to build strong enough frames, but nobody is pulling tractor trailers with rocket bikes... It's not going to be as easy to get this 1.6" cartridge up to the speed you want and need, and it's not possible to get that level of performance out of short recoil or blowback actions, so we're looking at a gas operation (or at LEAST delayed blowback, dynamic barrel).

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Varminterror said:

There was no bashing in my comment about Peter Thiel, but rather I simply pointed out that it's very plain to see that he did NOT make his billions by doing what his quote claims - he found ways to do something well, and obviously convinced folks like yourself that those were "10x better" than the existing products. Better, maybe, better marketed, eh, maybe, maybe even likely, but damned sure not 10x better. He made his wealth as an options trader, and built enough capital mass doing so to become a VC, and the snowball took off. Great for him, and it IS a repeatable process for those folks with an appetite for risk, but it also was NOT built on the back of his products or processes being "10x better" than anything before them. That quote was just grandstanding - which was my original point. What you're describing here also doesn't need to be 10x better than anything else in the market - and it doesn't need to be revolutionary in design, and frankly, it will be far more likely to fail if it IS revolutionary in design.

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Varminterror said:

My personal history, frankly, isn't any of your business, but I'm pretty open around here about it. I'm a chemical engineer turned business developer which has spent the last 20yrs in technology development and commercialization, along side a professional bull riding career which supplemented my income, along with operating a few other businesses and investments (predominantly good market picks and real estate), so I covered my first million in my early 30's by understanding how to make money, keep it, then make money make money. No I'm not a billionaire. But my passion and professional expertise is technology development and commercialization - helping grow ideas from the skunkworks into the real world, often working with venture capitalists like Thiel to bring dollars to the table to help put rubber on the road. This kind of thing is what I do every. single. day. Carrying ideas from R&D to Applications Teams, prototyping and piloting, beta testing, market demonstrations, and product launches... So this is another Monday morning 'ideation meeting' where I'd "look for leaks" in the existing idea-flow, and when we find ways to plug those leaks (in suitably economical ways), we end up with a market ready product.

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Varminterror said:

I DO do this professionally. I assumed, since you posited the question the way you did, that you might be interested in exploring how products like that are developed - and frankly, I'd argue that we DID develop set of parameters which would be VERY productive if passed to an engineering team to prototype this idea.

Design parameters to meet those standards were achieved above through our winnowing process in this thread (acknowledging that the goalpost you provided above was actually 2790fps with an 80grn bullet). Case length <1.08" to fit 80grn 6mm bullets with decent BC's into 1.68", case capacity >45grn H2O, preferring closer to 50grn H2O (which likely means Magnum/50AE or Gibbs caseheads to achieve that capacity with a ~1.1" case length), pressure standard will likely have to be 55-65kpsi, might need to be 80kpsi. Looking at the firearm to swallow this, we'll be feeding from something like Desert Eagle 50AE magazines, and we expect we'll have to use a gas operated action - acknowledging if we need 80kpsi, we'll either need an even bigger, beefier action, or we'll have to rely upon boutique alloys to keep size and weight down. Which I mentioned previously:

If we just need to exceed the 5.7x28 and 9mm, and NOT achieve the 2790fps cited previously, then I'd be much more confident in doing so with pressures possible from conventional brass cases rather than 3 piece cases, but without repeating the math provided in my recent post above to estimate the case dimensions, I'd bet we'd still need something larger than a standard bolt face (.473"). Pushing back that 6AE far enough to shorten that case to 1.0" and give access to lighter weight 6mm bullets with .6" nose lengths should have enough case capacity.

So for what it's worth - we're there. We have enough to establish a design for modeling, a little time in Quickload, a little time in SolidWorks, the results of which would further refine the design for prototyping.

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Varminterror said:

the performance standard of the 5.7x28 really isn't terribly impressive - it's effectively a 22WMR...

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Varminterror said:

It is a common observation of historical fact that the Automags were unreliable, and it WAS the public opinion of the design team that the pistol could not be made to be reliable at their price point and with the materials being used. They recognized the combination of the rotating bolt with a short recoil operated design just wasn't sufficiently reliable. And not surprisingly, the Automags weren't reliable, which is the primary driver for why the product failed in the market. That's history, that's not opinion.

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Varminterror said:

I've played with Saboted bullets quite a bit in centerfire rifle cartridges, and I do not believe it is a productive solution to what we're describing. The purpose of sabots (beyond sealing the bore, and focusing on this particular application) is to use a sub-caliber bullet in an oversized bore, which adds uneffective mass to the bullet, destabilizes the bullet in separation. I appreciate the anecdote of shooting 2" groups at 100yrds with a muzzle loader, which really reflects the fact the bar for muzzleloaders is really quite low - shooting smaller than conventional slugs isn't terribly difficult, but 2" groups for a centerfire carbine cartridge would be abysmal. The Rem Accelerators played this game as a factory offering, and we note that they were short lived. Shooting a 22cal bullet out of a 30-06 did add a lot of speed, but they really only had a market during an era when folks believed in "long range lasers," being 3400-4000fps cartridges despite really poor BC's. They were great for shooting prairie dogs at ~400yrds with a 30-06...

But in our application here, I don't see sabots as any particular advantage. Accuracy is a problem, and the advantage really isn't real (unless your goal is defeating armor).

Let's look at some known science as to why: There's a composite 77grn 10mm Auto load out there on the market, if memory serves, it hits 2300fps - not quite double the speed we see from a 180grn 10mm load. A 180 at 1200 has roughly TWICE the momentum of a 77 at 2300fps - and momentum is what is conserved in real-world, inelastic collisions, NOT kinetic energy, and we give up 20% momentum by using the underweight bullet instead of the standard load. Effectively, shooting the sub-weight bullet - or in our case, a saboted bullet, means we have LESS performance. If we need to defeat velocity-sensitive armor, sure, extreme speed makes a difference. But for anything else, the performance is reduced.

There does also exist a 10mm necked down to 30cal sabots with 22cal bullets. I forget what it's called, but it's obviously not terribly popular.

So I think this isn't a viable solution - if we compare necking down vs. running sabots, we're trading bore inefficiency (underweight bullet not holding as much resistance against primary and secondary combustion meaning less pressure and less retained pressure during expansion), for increased bore area (larger area * same pressure = larger force), so it kinda ends up a wash on performance, so we come down to the lost powder capacity and the inconsistent sabot separation driving an overall net negative. That's largely why 1) we don't see sabots being broadly used, and 2) only see armor penetration as the primary purpose of sabot rounds. If we have the opportunity to neck down, what are we gaining by using a sabot? Nothing really. We didn't sabot 6mm bullets into 308 cases, we just necked down and made the 243win.

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Varminterror said:

Yeah, but eh, where's the fun in that? Necking down, we lose bore capacity (same max pressure * smaller bore area = smaller force) and we lose case capacity, so we end up with less energy on the bullet than what we had from the full bore cartridge. Faster, for sure, but again, reduced momentum, reduced performance. We see things out there already doing this - 357sig, 357/44 B&D or Bobcat, 400 Corbon, 9x25mm (10mm necked to 9mm). In general, we don't neck these down very far, and they're never terribly high pressure rounds, because of the additional bolt thrust created by the shoulder thrust in rounds necked down farther. We need a more secure action lock up than simple short recoil if we're going to use a longer shoulder, necking down more than 1-2 calibers. And we're just not going to get to the level of performance you're seeking - even the relatively large 10mm Auto only has 25grn H2O capacity, which is only about half of what we've established we'll need to get there.

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Varminterror said:

I have a friend which runs a specialty components business, he 3D printed prototypes for magazines, but they don't hold up - his production models are injection molded, and he contracts the manufacturing. And those are 22LR magazines, not centerfire, large cartridge mags. The properties of polymers used, and the specific polymeric orientation of 3D printed products doesn't really lend it to being a great option for magazines, but it's certainly worthy of prototyping.

However, a specific concern I'd have for using any form of polymer magazines for this application is the extra thickness of the mag walls compared to metal mags - we'd be giving up potential COAL which we desperately need.

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gotboostvr said:

224 Boz I belive, or one of it's variants at least.

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