RogueRose
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Pressing a nitroglycerine / nitrocellulose mixture
about 55-60 years ago this combination was used in place of smokeless powder to make a caseless round (no brass) and it looks awesome (spec wise) and
it performed beautifully. It was meant for 22, 25 and 30cal rounds but only 22 was made.
Now there may have been a very small amount of something else added to this mix, something that would have HAD to burnt (turned to gas) and not fowled
the barrel, and it may have been a binding agent. It wasn't anything exotic like an azide, HMX, RDX, or any such thing - just to make sure we don't
go down that track.
I'm wondering what kind of pressures could be used to press a NG/NC combo as the bullet was pressed into the explosive to "seat' it onto the charge
(it had a nub to help hold charge in place).
I'm wondering if something like paraffin or even petroleum jelly might work, I'm talking about 1-2% total weight of the NG/NC mix or even super fine
wood dust (wood flour)??
The charge was so hard that it was very difficult to dent it with a very hard thumbnail and scraping with a blade (not slicing) really didn't remove
much material at all.
I'm wondering what kind of pressures (psi) would be expected to be used to create a charge like this that was very durable, keep in mind that the area
of a 22 is probably about 1/20 of an inch so if a press was exerting 15psi on a 1" piston, then that would be about 300PSI on the 22 charge.
I have no background in EM's but have seen people talk about compressing charges and it makes them more powerful (or detonate easier??). I'm
wondering what the upper limits might be for this and what would be the benefit, if any, of a higher compression ratio of the charge (besides taking
up less space and being harder to "scratch off" - both are MAJOR benefits though).
So at what pressure might it go BOOM? 
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Ozone
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You might want to look into propellant for the H&K G11. They started with nitrocellulose (NC), but had problems with cook-off. They then developed
a high-ignition temperature propellant (HITP) that used HMX.
See (in particular, the drawing):
https://armourersbench.com/2017/11/19/an-introduction-to-the...
A lot of information and pictures, an idea of the complexity of the propellant mixture--but no idea as to what the components are:
https://imemg.org/wp-content/uploads/imemts2006_Ashcroft_pre...
The stuff is progressive-burning (meaning rate increases with pressure), and they demonstrate cook-off relative to temperature on a hotplate--but the
buggers don't put any scale on the Y-axis. Time is log s.
Here is something about "ATK Thiokol’s energetic thermoplastic
elastomer" which was used with H&K's HITP (and a few development venues):
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2005/sm...
See also, "consolidated ball powder." I've seen something (maybe) similar when ball powder (NC) swelled with methanol is centrifuged.
I've been interested in this for a while. Although I've no interest in developing caseless ammunition, it's (the G11 is an alien-gun) intriguing, and
I do spend a great amount of time plumbing the depth of knowledge of internal ballistics (see Brian Litz at Berger) and how this translates into
achieving the best possible performance of the cartridges I hand load. The latter has involved (to great effect) applied Analytical Chemistry--more on
that when the project is done.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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macckone
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grain size of the propellant is important for even burning.
caseless ammo uses a nitrocellulose body that ignites.
most often with a center cavity filled with traditional 'double base' powder.
early use of nitrocellulose in pool balls was reportedly interesting as some were 'over-nitrated' and exploded.
https://www.smithsonianmag.com/smart-news/once-upon-time-exp...
This lead to caseless ammunition made of nitrocellulose which is fine for a single shot derringer and other guns that don't need a rapid rate of fire
and would also seem ideal for revolvers. A drawback in an automatic would be the round being pushed into a very hot breech leading to premature
firing when the 'plastic casing' ignites. Also known as cook-off, which can happen with metal casings as well.
This would seem ideal for sniper rifles as well since they are generally single shot and would not leave a casing.
Also nitroglycerin and nitrocellulose is commonly called 'double base smokeless powder'.
https://www.chuckhawks.com/smokeless_powder.htm
More modern 'caseless ammo' is made from other propellants that aren't as heat sensitive.
No clue what the improved propellants are but searching for dynamit nobel patents would be a starting point.
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RogueRose
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Thanks for the responses, I don't have time to read now, but will look it over later, looks like a lot of good information to start from! THanks
again!
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Herr Haber
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You can also check out modern tanks for details on the projectiles.
Many of them dont use copper / brass / steel cartridges anymore but a combustible cartridge and a metal base.
This metal base being the only part left after the shot is fired.
Thanks Ozone for reminding me of the G11 and it's insane rate of fire.
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