A_Mysterious_Stranger

I've noticed there is no repository for ballistic science documents the way there is for the Mechanized or the infantry forums (for example) so I decided to fix this. 
 
My first offering is dtic stuff from the past on some weird and novel ways to extend the L/D ratios of spin stabilized projectiles.   I originally learned about this from someone I was having a discussion with years back and hunting lead me to one of those discussions about bringing back the battleships on navweaps discussion boards where one of the posters (Zenmastur) laid out his master plan for Battleship resurrection.  Which included the aforementioned 'higher than 6:1 L/D ratio spin stabilized projectiles'.    It took awhile to hunt down but I eventually found some of the original documents that focused on novel projectile shapes (for a large improvement) and non-conical boat tails (for a much smaller improvement)   
 
Obviously this went nowhere insofar as I am aware, and I suspect they had drawbacks nobody addressed (like most do) but it's an interesting thing to look at anyhow.   Much of this is the work of one Anders S. Platou, who seems to be as prolific as the RAVEN guy. 
 
AN IMPROVED PROJECTILE BOATTAIL
 
 
AN IMPROVED PROJECTILE BOATTAIL. PART II.
 

Improving the Flight Performance of Projectiles 
 
 
MUZZLE-BLAST-INDUCED TRAJECTORY PERTURBATION OF NONCONICAL AND CONICAL BOATTAIL PROJECTILES
 
THE EFFECT OF VARIOUS BOATTAIL SHAPES ON BASE PRESSURE AND OTHER AERODYNAMIC CHARACTERISTICS OF A 7-CALIBER LONG BODY OF REVOLUTION AT M = 1.70
 
 
 
YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILES AND THE 155MM M549 PROJECTILE AT TONOPAH TEST RANGE-OCTOBER 1977
 
 

YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILE-B CONFIGURATIONS AT TONOPAH TEST RANGE--MARCH 1978
 
 
AEROBALLISTICS OF 9ORKSCRE1 PROJECTILES (12 page document)

 
 
 
AEROBALLISTICS OF CORKSCREW PROJECTILES (36 page document)
 

 

I've noticed there is no repository for ballistic science documents the way there is for the Mechanized or the infantry forums (for example) so I decided to fix this. 
 
My first offering is dtic stuff from the past on some weird and novel ways to extend the L/D ratios of spin stabilized projectiles.   I originally learned about this from someone I was having a discussion with years back and hunting lead me to one of those discussions about bringing back the battleships on navweaps discussion boards where one of the posters (Zenmastur) laid out his master plan for Battleship resurrection.  Which included the aforementioned 'higher than 6:1 L/D ratio spin stabilized projectiles'.    It took awhile to hunt down but I eventually found some of the original documents that focused on novel projectile shapes (for a large improvement) and non-conical boat tails (for a much smaller improvement)   
 
Obviously this went nowhere insofar as I am aware, and I suspect they had drawbacks nobody addressed (like most do) but it's an interesting thing to look at anyhow.   Much of this is the work of one Anders S. Platou, who seems to be as prolific as the RAVEN guy. 
 
AN IMPROVED PROJECTILE BOATTAIL
 
 
AN IMPROVED PROJECTILE BOATTAIL. PART II.
 

Improving the Flight Performance of Projectiles 
 
 
MUZZLE-BLAST-INDUCED TRAJECTORY PERTURBATION OF NONCONICAL AND CONICAL BOATTAIL PROJECTILES
 
THE EFFECT OF VARIOUS BOATTAIL SHAPES ON BASE PRESSURE AND OTHER AERODYNAMIC CHARACTERISTICS OF A 7-CALIBER LONG BODY OF REVOLUTION AT M = 1.70
 
 
 
YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILES AND THE 155MM M549 PROJECTILE AT TONOPAH TEST RANGE-OCTOBER 1977
 
 

YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILE-B CONFIGURATIONS AT TONOPAH TEST RANGE--MARCH 1978
 
 
AEROBALLISTICS OF 9ORKSCRE1 PROJECTILES (12 page document)

 
 
 
AEROBALLISTICS OF CORKSCREW PROJECTILES (36 page document)
 

 

I've noticed there is no repository for ballistic science documents the way there is for the Mechanized or the infantry forums (for example) so I decided to fix this. 
 
My first offering is dtic stuff from the past on some weird and novel ways to extend the L/D ratios of spin stabilized projectiles.   I originally learned about this from someone I was having a discussion with years back and hunting lead me to one of those discussions about bringing back the battleships on navweaps discussion boards where one of the posters (Zenmastur) laid out his master plan for Battleship resurrection.  Which included the aforementioned 'higher than 6:1 L/D ratio spin stabilized projectiles'.    It took awhile to hunt down but I eventually found some of the original documents that focused on novel projectile shapes (for a large improvement) and non-conical boat tails (for a much smaller improvement)   
 
Obviously this went nowhere insofar as I am aware, and I suspect they had drawbacks nobody addressed (like most do) but it's an interesting thing to look at anyhow.   Much of this is the work of one Anders S. Platou, who seems to be as prolific as the RAVEN guy. 
 
AN IMPROVED PROJECTILE BOATTAIL
 
 
AN IMPROVED PROJECTILE BOATTAIL. PART II.
 

Improving the Flight Performance of Projectiles 
 
 
MUZZLE-BLAST-INDUCED TRAJECTORY PERTURBATION OF NONCONICAL AND CONICAL BOATTAIL PROJECTILES
 
THE EFFECT OF VARIOUS BOATTAIL SHAPES ON BASE PRESSURE AND OTHER AERODYNAMIC CHARACTERISTICS OF A 7-CALIBER LONG BODY OF REVOLUTION AT M = 1.70
 
 
 
YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILES AND THE 155MM M549 PROJECTILE AT TONOPAH TEST RANGE-OCTOBER 1977
 
 

YAWSONDE FLIGHTS OF 155MM NON-CONICAL BOATTAIL PROJECTILE-B CONFIGURATIONS AT TONOPAH TEST RANGE--MARCH 1978
 
 
AEROBALLISTICS OF 9ORKSCRE1 PROJECTILES (12 page document)

 
 
 
AEROBALLISTICS OF CORKSCREW PROJECTILES (36 page document)
 

 

Keep in mind those are operating pressures not maximum average pressure (MAP). So the MAP for the new rounds will probably be 80-90KPSI.
 
Chamber pressure doesn't really depend on the internal volume of the case, it's a measure of force per area (the internal surface area of the case). And there are a bunch of different chamber pressure measurements.

What they are doing is exploiting two facts about CT ammunition, which is that there is no portion of the case that is unsupported and that the case is no longer subject to the plasticity of brass (which is in the 75,000 PSI+ chamber pressure range). Basically, if you run really high pressures with a brass case, depending on how that case is hardened, the brass will become plastic and braze itself to the bolt face. Bad. If your polymer case is sufficiently strong, then you avoid this both by using a different material and by having a round that is completely supported in the chamber.

And of course, if you can get away with it, more chamber pressure is better. Now, I think there are still a bunch of technical hurdles that you'd have to overcome to make this concept work, so I'm not really sure how successful it will be. And I've not heard terribly good things about how the program is being run.
 
 
Yes. The new round is some 6.5-6.8mm ultra high velocity thing.
 
 
I've heard various things, from 110 to 140gr 6.8mm EPRs, but in general it's supposed to have a very high muzzle velocity. The round is the brainchild of Dr. James Newill, and I believe Mark Minisi is working under him. Newill... Has a certain reputation for fantasy among some of my sources.
 
 
That's exactly what they are doing. What kicked this off was the CT Carbine with an experimental ARDEC smart optic bolted to it. That optic is nowhere near ready for prime time, but you can't stop stupid.

Upping the chamber pressure is possible without increasing ammunition weight much, if you can stop it welding the brass to the chamber/bursting the barrel. Getting a faster burning powder (or just putting loaded ammo into a tumbler and letting the powder beat itself to dust) will release more energy before the bullet has started moving appreciably, and so should improve efficiency giving more performance.
 
Adding weight and cost to the rifle is guaranteed, of course, so the total weight of the system will be more than the M4 (but hopefully less than a 60's tech gerpercer with the same sectional KE downrange)

I think @Sturgeon will chime in on this program, as I'm sure he knows more of the details.  But basically this is in line with the series of extremely ambitious US small arms projects that don't really go anywhere.

Chamber pressure is an interesting topic, and one that is under-studied in small arms.  Tanks do run much higher chamber pressures in their guns, it's true.  I think some APFSDS rounds are north of 100KPSI, which is roughly double what a typical assault rifle round burns at.  But just scaling that technology down has some issues.

The first is that if you try to run those pressures with a conventional cased round the casing will weld itself to the chamber and stick.  Ammunition for the 120mm NATO and 125mm Russian guns is semi-caseless.  That works fine for a gun that's loaded manually, or even one that's serviced by an autoloader.  But is semi-caseless ammo tough enough to survive the breech of an autoloading weapon?  Try just cycling some rounds through an AR-15, they get gouged to hell just being run through the action.
 
Throat wear is another issue.  Tank guns aren't expected to shoot very often, so it's OK that those tubes only last a few hundred rounds.  They have magical fire control systems, so they hit what they are aiming at most of the time.  The interplay between chamber pressure and throat wear is very complex, but getting the propellant gas that hot is likely to cause some acceleration of throat wear.

Finally, running a gun at that pressure requires more care in the production and maintenance of everything.  Tank guns get babied and cooed over, infantry rifles do not.  Tank ammo is made extremely carefully and precisely, infantry rifle ammo is not.  Tank gun barrels are made entirely from electroslag refined steel, which is considered a strategic material.  In rifles only the bolts are.
 
Running the pressures into the stratosphere has a lot of mathematically attractive benefits, but the real-world challenges are considerable.

Thought experiment; what happens if we take the same cartridge, same case, same propellant mass and chemistry, same projectile, only in one cartridge the propellant is more finely divided so that it burns faster?

For simplicity's sake, let's ignore secondary effects like "LOL, the propellant peak pressure exceeds the yield strength of the cartridge and/or breech and the gun explodes itself" or "the burn rate of the propellant becomes more consistent by one sigma due to the effect seen in hi-lo pressure guns."

This is an interesting thought experiment because my reading leads me to the conclusion that the designers of tank guns know the answer, and the designers of small arms do not.

CT ammunition uses less propellant because it is more thermodynamically efficient.
 
 
The CT Carbine uses a rising chamber design, rather than a swinging chamber as in the LMG.
 
 
As far as I know The Dentist Roberts has no connection with these programs, although some of the people associated have similar views on ballistics, from what I hear.
 
 
Good job finding those docs. Yes, Newill and Minisi both work for ARL, last I checked.
 
 
Remember, ARDEC's primary function is to be welfare for smart people. The third arm thing isn't going anywhere.
 
 
I think the US Army is strongly considering a magazine-fed support weapon, yes - though NGSAR does not specifically outline that feeding mechanism.

It looks like the goal is 600 meters effectiveness against Level IV with tungsten ammo, which isn't so bad as I'd initially feared.
 
 
Knox blew up a lot of test barrels with their ammo, from what I hear.
 

Regarding the apparent ~$13 unit cost of XM1158.
 
I was going through past year editions of Army Mantech's annual brochure, and the FY15 one mentioned a new start of "7.62mm Advanced AP Penetrator & Assembly Cost Reduction", the following three issues have had a 'tungsten carbide penetrator & assembly cost reduction' section.
 
FY16
FY17
The current FY18 brochure specifically mentions XM1158.
 
I also found an army.mil article that talks a little bit about it and has better pictures.
 
 

So just sharing a bunch of aforementioned links that may be of interest:
 
First batch are a series of technical reports about a Knox Engineering company cartridge design for lightweight 5.56 NATO centering around 'enhanced propellant' and 'alternative cartridge case' (basically a straight-walled design):
 
ENHANCED PROPELLANT AND ALTERNATIVE CARTRIDGE CASE DESIGNS


 
 
DEVELOPMENT OF A LIGHTWEIGHT AMMUNITION CONCEPT USING AN ALTERNATIVE CASE MATERIAL AND ENHANCED PROPELLANT



They're very similar but many of the ideas seem to overlap with what we know so may be of interest even if they are over a decade old.
...
 
Component Technology Investigations for Light Machine Gun Applications
 
- 2005 NDIA presentation on LMG technology concerning lighter barrels and various catridge concepts (including the Knox one above, and aluminum cases.) 
...
 
Lightweight Small Arms Technologies (Formerly known as…Lightweight Machine Gun and Ammunition)
 
- 2005 presentation on LSAT for NDIA concerning machine guns.  Like alot of it more than a decade old, but the details are interesting all the same I think as far as internals and tradeoffs go.
...
 
ALTERNATIVE CARTRIDGE CASE MATERIAL AND DESIGN



This one is more about polymer case designs and the challenges.  more than a decade old but may still be of interest again.
...
 
A new machine gun - the right weapon for today's environment
 
A General Dynamics 2012 presentation on Machine gun improvements and design and seems focused on the LWMMG concept.  Warning includes at least one mention of 'Tactical Overmatch'
...
 
LIGHTWEIGHT AMMUNITION DESIGN - 8550
 
- 2009 presentation by Colt on a 'hybrid' cased/caseless 'modular' design  and a polymer spiral case for .50 BMG ammunition.  Interesting for the 'modular' design being a 'caseless' cartridge inside a brass case with two giant holes cut in the side.
...
 
SHOULD THE U.S. ARMY ADOPT NEW 5.56MM AMMUNITION CARTRIDGE DESIGNS TO REDUCE OVERALL AMMUNITION WEIGHT?



Found this in with what I was digging through, decided to keep it anyhow since it is something Sturgeon has interest in, although he may have already seen/read it.   Does cover some of the concepts mentioned above though as well (the colt modular concept, as well as aluminum, steel, polymer, telescoped, etc.)
 

So I had a bunch more links on RAVEN, these don't seem to have been posted, so I'm posting them.   Dr Eric Kathe is a prolific guy: 
 
http://www.dtic.mil/dtic/tr/fulltext/u2/a435128.pdf <-  this one is a 317 page thesis by Dr Kathe on RAVEN in relation to other recoilless concepts
 
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA398942 <-  pdf download if you click on the link.   
 
Google cache link here:http://webcache.googleusercontent.com/search?q=cache:6eBVulAzScsJ:www.dtic.mil/get-tr-doc/pdf%3FAD%3DADA398942+&cd=5&hl=en&ct=clnk&gl=us
 
It's another technical paper by Dr Kathe in the same vein as the above, but with fewer pages.
 
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2015/armament/wedKathe.pdf < - powerpoint along the lines of what you posted a few years back, but with some other differences (I think) which analyzed alternatives
 
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2015/armament/MondayKathe_Tutorial.pdf <- another powerpoint.  With the monday/wednesday thing  I think it wsa part of a larger seminar in 2015.  you posted one of those originally (the Tuesday one) 
 
Some technical reports on RAVEN and the tech demonstrator
http://www.dtic.mil/dtic/tr/fulltext/u2/a597442.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a591200.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a504316.pdf
 
And another powerpoint:
 
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2010/armament/WednesdayLandmarkAMikeBixler.pdf
 
I'm also fascinated by RAVEN and it has many nifty implications regarding 'light weight without losing performance'  as far as recoilless technologies go.  One was for improving man portable firepower (mentioned in the first pdf Collimatrix posted   in the original post.

http://www.dtic.mil/dtic/tr/fulltext/u2/a007151.pdf
 
This is one of those things you always find when you do diving into DTIC or some other site for unrelated purposes but is still interesting - a 1975 study on extending ranges of  US artillery.
 
 
It's one of those interesting reads because it highlights cold war era thinking.  Whether it has merit today or more than historical interest I'll leave up to others.  It does have some really interesting charts though (like the velocity/momentum a artillery round needed for a given range)