Just discovered this board. I'm interested in all things related to gun technology. I have many hobbies related to small arms but am also interested in large gun. I saw this post and looked at the UDLP web site. I can't figure out how Sandbagger's original question resulted in so many comments on liquid propellant. The web site talks about using some solid propellant modular charges in a 105mm cannon. Haven't quite figured out why they need variable volume to do this? Anyone know what advantage variable volume would provide?

I think the reason I took it to the liquid propellant area was that judging by the variable volume charge chamber, and after reading the tech stuff on the sight: one of the concepts studied by UDLP for several years has been liquid propellants. Even in continuing to use solids, liquids can be formulated to achieve greater launch controls of the projectiles. ElectroThermal Chemical solid propellants, ignited by high electrical impulses, are progressing better than was anticipated several years ago. We basically compiled "suggested" outputs based on the fact that for any given propellant material, liquids generally allow us greater efficiencies (by varying the amount of air/oxygen to interact during the combustion process). Having a chamber that can adjust its internal volume effectively mimics a piston engine: changing your combustion envelope to allow a lean mix or a rich mix to get the best economy can alter the output power (and velocity and range of the shell). Easiest to describe it as a firecracker in an upside-down can. Setting off a fire cracker inside a coffee can, and then another one in a soup can, there will be greater pressures in the soup can because it has a smaller internal displacement, and the result for the same amount of powder is a higher velocity than the larger coffee can. With the advent of improved mixes in solid propellant, greater efficiences are being reached. For a time, only liquid propellants seemed to offer such controllable combustion rates: pump in more or less fluid depending on the ballistics you want. A variable volume chamber would be ideal for such fuel: rather than carrying several different sizes of solid propellant charges, you just change the size of the combustion chamber and pump in the right amount of liquid propellant. Mortars have the benefit of "clipping on" additional solid propellant charge rings, but most artillery guns have a few different sized propellant bags that can be combined to offer differing ballistic trajectories, ranges, and velocities. If you use maybe a Charge 3 in two different sized chambers, you may get differing abilities of range, flight, and velocity for the same weight of shell, just because there may be more or less pressure exerted on the shell. If the V2C2 tech fully matures and finds favor, it may well eventually reach the abilities that were hoped for in using the liquid propellant, fixed chamber systems..

The SP version looks great. I noticed that they had some statistics on their site showing what percentage of artillery fire came from SP versus towed cannons. 13,923 rounds from SP Palladins. 516 rounds from the towed M198 I expect the SP version would prove invaluable.

"Variable volume" The theory goes (as I'm sure you know) that you can add any number of charges behind a shell, but at some point the burn rate doesn't produce the same incremental improvement in velocity because the gas expands faster than the cartidges burn down. However, if you have a WIDER charge as well, the build up of the gas pressure wave is much faster. It's like the difference between .223 and 5.56mm - theoretically the same caliber, but what matters is speed at which the propellant burns and a broad charge will always produce more gas than a narrow charge. Hope that helps.

Politics etc! Looks like an interesting technology, but the range improvements are no better than achieved with ERAP, base bleed shells or fitting 52 cal, i.e 50% in getting from 20km to 30km. I note UD are making a logistics case for using propellant in inventory, an odd marketing idea; you'd think there would be other stand-out features. I cant see how v2c2 105mm replaces the M119 105mm Light Gun of 4,520lbs (2050kg). M119 was adopted from the Brits after the Falklands because it proved amazingly reliable (some guns fired 400 rounds with zero problems), has a 20km range (RAP), 6 RPM rapid and 3 RPM sustainable fire and it met the Light Division/ Independent Brigade mobility requirement, especially for air mobile/helicopter, parachute and amphibious operations. You can string one from a Blackhawk, two from a Chinook, or one plus a fully ammunitioned towing vehicle (HMMW); Chinook can't lift v2c2. Which is why the US Army and USMC have selected the British M777 155mm towed howitzer to replace M119; at 10,000lbs (4218kg) it is much heavier but still liftable by Chinook. It also has a 30km range (with only a 39 cal barrel). 155mm is also double the weight of a 105mm shell. Our M777 order for 700 systems is interesting since there are only 352 M119 in inventory. This implies that we are doubling the air mobile artillery allotment. Since M109 and M777 can use the same ammunition (in need) this standardizes our artillery logistics on 155mm. For all its merits, UD have produced a light gun (105mm) which is too heavy to be used as a light gun and too light to be used as a medium gun. Not a good compromise!

M777 is replacing a fair number of M198's as well, not just 105mm pieces. I believe the Marines intend to fully replace the M198 with M777.

Its a wholesale replacement in the Army as well. The M198 wil lleave the inventory with the advent of the M777. The M198 has been adequate....I wouldn't say much more.

A few questions come to mind - Could this technology be used for 155mm? - What would the range increase be? - Can it be used with RAP? Does anyone have any ideas?

Since UDLP is the main contractor of M109 stuff (we used to know them as FMC), most likely they are considering the application into the 155mm system on these vehicles (there was for a time a plan to incorporate Crusader tech spin-offs into an Improved Paladin (an M109A7 maybe?), but I haven't seen any information on this for a few months now). Most likely, we will have to wait for the FCS NLOS-C. It could prove ideal, if UDLP can get 40km ranges or greater out of 39 caliber barrels: there would be a weight reduction (the extra 40 or so inches of barrel going from a 52 to 39 caliber gun could easily save a couple hundred pounds, plus lower stresses on the trunnions result from shorter and lighter barrels, and there is greater clearance overall lengthwise when transporting)..

doggtag, when you talk about firing a "zone 3" with two different chamber volumes I assume this means you fire the same amount of propellant and the adjustable chamber allows you to get different performance using the same bullet. Good observation. Something that those of us working with small cased ammo never think about trying I guess. My hobby is in the realm of handgun and shotgun ammunition. Worcester, when you say "broad" versus "narrow" charge are you really saying "slower" versus "faster" burning? Good point too about the marketing idea of using existing charges. It appears that they are talking about using the same charge as the larger 155 guns but I thought they used cloth bags of propellant?