http://www.dtic.mil/ndia/2008gun_missile/6337GimmyKirk.pdf

Looks like an attempt to ballistically match the HEI round to the API.

Question to Tony:
Are 30x173mm PGU-14/B Armor Piercing Incendiary (API), 30x173mm PGU-13/B High Explosive Incendiary (HEI) and 30x173mm improved High Explosive Incendiary (IHEI) usable in Mk44 Bushmaster II canon? That new HEI kooks quite good to be used in IFV's too...

I believe that the MK44 can use any of the 30x173 family (except for the ancestral Oerlikon KCA round, which was electric-primed). Being externally driven the MK44 is unaffected by any pressure-curve differences, and being slow-firing it doesn't hammer the light alloy cases.

Thank you.

Does anybody know how to get to the rest of the PDFs/PPTs, for that conference. The only one that comes up when I click on the link for the 2008 Gun/Missile symposium is the agenda. What the heck?

There are links in some of the items in the agenda, IIRC the link is in the name of the presenter.

Stupid setup, imo. Or they should at least have made them more obvious.

This doesn't really have anything to do withe the PGU-13, but I just read that the Army is canceling the PGMM,(precision guided mortar munition) dues to not enough funding in the upcoming budget. Wasn't this thing just about ready to go into service? Although with something like Netfires/NLOS coming on-line circa 2010-2012 it may seem kind of redundant.

Redundant capabilities, perhaps - but once you have to start paying for rounds fired, the redundancy ends

Ya gotta click on the Agenda (it should be an underlined link),
then, like gewing said,
you just scroll down thru all the presentations on the Agenda list,
and where a person's name is underlined, you can view the pdf of that seminar.

The biggest suck part of it isn't that some of the presentations and meetings aren't selectable,
it's that just about every presentation was turned from a decent PowerPoint, with all the videos intact,
into a pdf that doesn't let you view the videos.
At least any version of Adobe I've used doesn't.

One for Tony W,
and anyone else in the know:
something I've never really looked into before.

I'm well aware that, especially during WW2, it was discovered that lengthening a barrel's calibers improved its velocity (allowed more of the propellant to efficiently combust and impart more of its energy to the projectile). Seems to work well enough with artillery, too: a 155mm gun with a 45- or 52-cal tube can impart more energy (higher velocity) into the shell and achieve greater ranges over a 39-cal tube (although certainly a more aerodynamic shell helps the process).

My question is: I'm aware that, typically, 30x173mm seems to be becoming the NATO standard norm (or whatever the Int'l STANAG is now),
but is there as STANAG/commonality around using the same barrel length from one cannon to another?
Meaning, does the Bushmaster Mk44 series gun have the same barrel length/calibers as, say, the Mauser 30mm gun on the Puma?
(or for that matter, each of the barrels of the GAU-8 cannon?)
I'm asking because I'm curious if there is a set ballistics table that the ammo is rated for, for a specific barrel length.
(would there be minimum acceptable barrel lengths where it would be unsafe to use the ammo,
and at the other extreme,
would there be a barrel length that beyond which, any more useful energy can't be drawn out of the combusting propellant...?)

Or is it more along the lines like we discussed with that other thread about using US ammo, initially patterned for the L44 M256 120mm tube, and certifying it to fire from the L55 gun (a tube some ~1&1/3 meters longer) ?

Just curious. It's something I've never really delved into.

Thx.

Optimum barrel length isn't a simple issue, but was well understood long before WW2.

There is an maximum-velocity barrel length for any given cartridge and loading. Shorter barrels will not make full use of the propellant gas; longer barrels will result in the friction drag of the projectile in the barrel becoming greater than the remaining thrust from the propellant, so the projectile begins to slow down (theoretically, a really long barrel would result in the projectile coming to a dead halt in the barrel). However, this is not particularly critical - the curve of muzzle velocity vs barrel length is quite gentle. So it is possible to shorten a barrel quite a lot without losing too much velocity, and this is often done (in military weapons in particular) because the advantages of having a shorter weapon are held to outweigh the velocity loss: the US Army's current preference for the M4 Carbine over the M16 rifle being a (controversial) case in point.

The reason that velocity increases with barrel length in 155mm guns is also connected with the fact that longer barrels tend to come with larger chambers to take more propellant. The two factors need to be taken together: increasing the barrel length alone will usually result in only a small increase in velocity, while increasing the propellant in the same barrel length will result in a small increase in velocity but a big increase in muzzle flash and blast (very short-barrelled .357 Magnum revolvers providing a good illustration of this).

Barrel lengths of the various 30x173 guns do vary. The latest version of the Mauser MK 30 (the MK 30-2) has a longer barrel than the earlier general-purpose (now MK 30-1) gun because it is primarily intended for AFVs to use in ground fighting, so armour penetration is an important criterion: the cartridge is a bit marginal against latest-generation light AFVs so every bit of velocity matters!

One historical case: the British WW2 6 pdr tank/anti-tank gun was initially made with a 43-cal barrel because that was all that could be done with the available machinery. Once better machinery was obtained, barrel length went up to the designed 50 cal (as it was from the start in the US-made version of the gun). Another historical case: the 'male' versions of the WW1 British tanks had long-barrelled 6 pdr naval guns, but these were drastically shortened (by the simple expedient of sawing off much of the barrel) to stop them from getting stuck in the mud. The ammo stayed the same (the muzzle blast must have been spectacular) and the velocity loss didn't matter in that application.

Why cancel something as potentially useful as PGMM?

It was only fielded late last year:

http://www.strategypage.com/htmw/htweap/ar...s/20071126.aspx