Understanding CT ammo finer details

[Sten]

So, for a while I've fascinated about Cased Telescoped Ammunition (CT ammo for those weird people that like acronyms), after, of course, laughing at the idea like any uninitiated simpleton (dum fix wat aint broke!) until I actually understood the idea and a presentable firearm came along and caught my interest, the current iteration of the Textron carbine/rifle/whatever in the NGSW program... because until this point all small arms examples were either goofy as fuck (Dardick), stillborn (Ares AIWS), or weirdly specific (Steyr ACR being and open "bolt" flechette gun.)

 

Then I researched and talked to knowledge people and comprehended the advantages of the concept, along with plastic cartridge cases: The near total elimination of small parts and movements from a gun's action, now using simple large parts and gross movements, the controlled nature of the feeding and ejection cycle, the cartridge case being fully supported in the chamber which allows for simpler design and analysis along with higher pressures, a more compact design (albeit highly dependent on the external constraints and capacity and projectile proportions), a potentially much simpler and stronger breech and locking mechanism, sealed ammunition, cannelure free sleek bullets, no more worries about hardened penetrators tips eroding the finish of the gun's inside, the ability for the gun to be able to function even with a severe misalignment of the chamber and barrel, etc... In short I was sold on the concept.

 

Yet... I never quite understood a few, small and not very often talked details about this type of ammunition configuration. So I kept researching, learned a few things, saw the historical development, older takes on the idea, which also raised more questions:

 

The first being, how is the projectile seated in the current version of Textron's Cased Telescoped ammunition? As you can see the only solid point of contact the bullet has is of the ogive on the cap, which stops it from going forwards under handling and provides both a seal of the powder chamber and pressure for the shot start... but nothing apparently stops the bullet from going further inside the case.

 

 

From what I could gather talking with another engineer and gunsmith that did research on the subject, the bullet apparently is seated on a bed of compressed spherical powder... that.. can work... I guess... but it sounds extremely questionable, specially in regards with consistency, but perhaps it work. But that is not the only reason I'm questioning this detail:

 

 

As you can see on this patent by Eugene Stoner the cartridge has the same sort of contact of the cap and ogive, but the bullet base also rests on three ribs/webs (technical terms are the hardest part of translation.) Those "things" also apparently serve to improve flow of the plastic during injection molding and to strengthen the case at a minimal internal capacity penalty

 

This way of doing things seems like the natural and proper way of seating a bullet, solidly and repeatably... so the Textron version looked so weird I imagined they were gluing the bullet like True Velocity possible does on their ammo, they aren't also using the canellure or other type of groove to secure the bullet (not that it would be a good idea)... so why did Textron opted for what they are using? Reality often is unintuitive as fuck  so there must be a reason for that.

 

Other big question I always had was how exactly the obvious issue of gas leakeage, analogous with a revolver, and all the bad joojoo that issue brings was going to be corrected. Thankfully that question was partially answered by the well known Textron's patent for the operating mechanism, were they explore all sorts of solutions for this problem. The basic idea is to squeeze the case against the barrel so as to close the gap. Of all their solutions, the one that uses a bolt seems like the more reasonable one (the other ones involves a screw-on breech or a ratcheting mechanism...)

The only issue left on this aspect is what sort of mechanism Textron is currently using... hope they win so we will know.

 

If more people could shine a light into those finer details I would greatly appreciate their help.

 

Stoner's Patent: https://patents.google.com/patent/US4770098A/en

Textron's patents: https://patents.google.com/patent/US9267772

And https://patents.google.com/patent/US9267772

 

 

[Sturgeon]

On 9/30/2020 at 1:52 PM, Sten said:

So, for a while I've fascinated about Cased Telescoped Ammunition (CT ammo for those weird people that like acronyms), after, of course, laughing at the idea like any uninitiated simpleton (dum fix wat aint broke!) until I actually understood the idea and a presentable firearm came along and caught my interest, the current iteration of the Textron carbine/rifle/whatever in the NGSW program... because until this point all small arms examples were either goofy as fuck (Dardick), stillborn (Ares AIWS), or weirdly specific (Steyr ACR being and open "bolt" flechette gun.)

 

Then I researched and talked to knowledge people and comprehended the advantages of the concept, along with plastic cartridge cases: The near total elimination of small parts and movements from a gun's action, now using simple large parts and gross movements, the controlled nature of the feeding and ejection cycle, the cartridge case being fully supported in the chamber which allows for simpler design and analysis along with higher pressures, a more compact design (albeit highly dependent on the external constraints and capacity and projectile proportions), a potentially much simpler and stronger breech and locking mechanism, sealed ammunition, cannelure free sleek bullets, no more worries about hardened penetrators tips eroding the finish of the gun's inside, the ability for the gun to be able to function even with a severe misalignment of the chamber and barrel, etc... In short I was sold on the concept.

 

Yet... I never quite understood a few, small and not very often talked details about this type of ammunition configuration. So I kept researching, learned a few things, saw the historical development, older takes on the idea, which also raised more questions:

 

The first being, how is the projectile seated in the current version of Textron's Cased Telescoped ammunition? As you can see the only solid point of contact the bullet has is of the ogive on the cap, which stops it from going forwards under handling and provides both a seal of the powder chamber and pressure for the shot start... but nothing apparently stops the bullet from going further inside the case.

 

 

From what I could gather talking with another engineer and gunsmith that did research on the subject, the bullet apparently is seated on a bed of compressed spherical powder... that.. can work... I guess... but it sounds extremely questionable, specially in regards with consistency, but perhaps it work. But that is not the only reason I'm questioning this detail:

 

 

As you can see on this patent by Eugene Stoner the cartridge has the same sort of contact of the cap and ogive, but the bullet base also rests on three ribs/webs (technical terms are the hardest part of translation.) Those "things" also apparently serve to improve flow of the plastic during injection molding and to strengthen the case at a minimal internal capacity penalty

 

This way of doing things seems like the natural and proper way of seating a bullet, solidly and repeatably... so the Textron version looked so weird I imagined they were gluing the bullet like True Velocity possible does on their ammo, they aren't also using the canellure or other type of groove to secure the bullet (not that it would be a good idea)... so why did Textron opted for what they are using? Reality often is unintuitive as fuck  so there must be a reason for that.

 

Other big question I always had was how exactly the obvious issue of gas leakeage, analogous with a revolver, and all the bad joojoo that issue brings was going to be corrected. Thankfully that question was partially answered by the well known Textron's patent for the operating mechanism, were they explore all sorts of solutions for this problem. The basic idea is to squeeze the case against the barrel so as to close the gap. Of all their solutions, the one that uses a bolt seems like the more reasonable one (the other ones involves a screw-on breech or a ratcheting mechanism...)

The only issue left on this aspect is what sort of mechanism Textron is currently using... hope they win so we will know.

 

If more people could shine a light into those finer details I would greatly appreciate their help.

 

Stoner's Patent: https://patents.google.com/patent/US4770098A/en

Textron's patents: https://patents.google.com/patent/US9267772

And https://patents.google.com/patent/US9267772

 

 

Have you read the paper I co-wrote on the subject? http://armamentresearch.com/wp-content/uploads/2020/01/ARES-Research-Report-No.-7-Cased-Telescoped-Ammunition.pdf

The propellant in Textron's CT ammunition is heavily compressed, and as far as I know that's how they achieve consistent seating. According to Kori Phillips (you can read my interviews with her here, here, and here) their ammunition is somewhat more accurate than regular Army ammunition so it seems to work ok.

Textron's design uses a rising chamber. You can see a reasonable approximation of how it may work here: 

 This is partially based on the ARES design, to which it is related.

You can see how the machine gun works here:
 

 

[Sten]

Yes, I have read the paper, but it has been a while so I probably forgotten stuff, so a re-reading is in order. That goes for the interview as well. I knew Textron was using a compacted powder bed, but it sounded so weird I wanted confirmation. Doing probably simplifies the molding process and does not lock you into a specific bullet shape. I think I'm starting to understand the reasoning behind it.

 

As for the action displayed, I'm also aware of them. To be frank I haven't paid much attention on the LSAT or MGs in general, more interest on the rifle and rifles in general. That VPN's animation sure is handy in explaining the concept, but he based it off the first part of the patent, the one that just displays the idea of a rising chamber and rammer, without the so called headspacing solutions. As it's I guess you can get away with just sizing the chamber and case just right, specially if one remembers cases also expand axially not just radially. But actually forcing the case to mate against the barrel would make a better consistent seal and would lax the fitment of the actual chamber. After all they went to the trouble to patent it... but maybe they can get away without using nay of those, other designs did like the Steyr ACR.

 

Other people, with extensive knowledge of firearms and engineering and which are keeping track of the program, which I have spoken questioned the accuracy of the animation "That animation is hilariously incorrect"... and considering how misleading and vague patents can be I will keep it as a possibility, but neither will take his word as gospel because no further confirmation was provided.

 

In anyways, thanks for the info and for clarifying the point about the seating. I will be sure to re-read the paper and the interview.

[Sturgeon]

36 minutes ago, Sten said:

Yes, I have read the paper, but it has been a while so I probably forgotten stuff, so a re-reading is in order. That goes for the interview as well. I knew Textron was using a compacted powder bed, but it sounded so weird I wanted confirmation. Doing probably simplifies the molding process and does not lock you into a specific bullet shape. I think I'm starting to understand the reasoning behind it.

 

As for the action displayed, I'm also aware of them. To be frank I haven't paid much attention on the LSAT or MGs in general, more interest on the rifle and rifles in general. That VPN's animation sure is handy in explaining the concept, but he based it off the first part of the patent, the one that just displays the idea of a rising chamber and rammer, without the so called headspacing solutions. As it's I guess you can get away with just sizing the chamber and case just right, specially if one remembers cases also expand axially not just radially. But actually forcing the case to mate against the barrel would make a better consistent seal and would lax the fitment of the actual chamber. After all they went to the trouble to patent it... but maybe they can get away without using nay of those, other designs did like the Steyr ACR.

 

Other people, with extensive knowledge of firearms and engineering and which are keeping track of the program, which I have spoken questioned the accuracy of the animation "That animation is hilariously incorrect"... and considering how misleading and vague patents can be I will keep it as a possibility, but neither will take his word as gospel because no further confirmation was provided.

 

In anyways, thanks for the info and for clarifying the point about the seating. I will be sure to re-read the paper and the interview.

 

It's probably inaccurate. Not sure about "hilariously". I'd be surprised if it weren't still a rising chamber, for example.

[Sten]

Yeah, a lifting chamber is pretty much granted. But there are several ways to accomplish it... it would be hilarious if in the final iteration of their design they went for a Steyr ACR style with the locking roller. They certainly got rid of some of the bulk, that little protrusion near the magwell is gone in the last gun they showed us.

[Sturgeon]

4 hours ago, Sten said:

Yeah, a lifting chamber is pretty much granted. But there are several ways to accomplish it... it would be hilarious if in the final iteration of their design they went for a Steyr ACR style with the locking roller. They certainly got rid of some of the bulk, that little protrusion near the magwell is gone in the last gun they showed us.

 

I think the HK redesign is bigger, actually.

[Lord_James]

Would improper feeding cause the plastic CT ammo to spill its powder, or tilt the bullet? 

[Sturgeon]

16 hours ago, Lord_James said:

Would improper feeding cause the plastic CT ammo to spill its powder, or tilt the bullet? 

Only if the feeding was ludicrously improper. That can happen with some jams with brass cased ammo for example.