Man-Portable Mini-Guns?

[Rupert]

Originally Posted by Polydamas

Humans divide continua into discontinuities, but I thought that the reason cannons start at 20 mm was that at around that calibre, its worth putting a bursting charge in the round, and that gives a weapon capabilities which a MG does not have?

At least that was the old German army thinking wasn't it?

The old Soviet 14.5mm round has had a somewhat useful HE round for decades now. The border between 'too small', and 'good enough; is pretty nebulous - for some applications a 20mm cannon can't fire an explosive shell worth having, but for other uses even a 14.5-15mm gun can. You can see this in the relatively low kinetic energy of a lot of 20mm cannons - in order to get a decent amount of HE into the shells they have to be thin-skinned, and that means they can't be fired at high muzzle velocities.

This is one reason for the slow trend towards 25mm cannons as the 'light cannon' - you can get a reasonable amount of HE and a high velocity in the same gun. Meanwhile, 37-40mm cannons seems to have been found to be too heavy for most uses, and 30mm is the common 'large' cannon, so the calibres are converging (which would make the Mauser BK-27 27mm cannon the ultimate 'fusion' weapon, but it doesn't seem to have been very widely adopted).

[HANS]

Originally Posted by Bathawk

DO man-portable mini-guns exist? They have always been popular in action films like "Predator" and "Terminator 2: Judgment Day" But I read somewhere (at least in the "Heroes Unlimited GM's Guide" that such weapons are pure fantasy and not viable, at least as a "man portable weapone

No. If you want them to be, I wrote one up in High-Tech, p. 136, cause of course I get it, they look cool.

The GE Microgun (AKA XM214 6Pak) was never a viable contender, as it, too, was never intended to be manportable. Since it couldn't do anything its larger cousin, the Minigun, could but fired a weaker cartridge, it rightfully never entered production and nobody bought it.

Originally Posted by Bathawk

Even if a true "rotating barrel gatling-gun" like weapon doesn't exist, what would be the closest equivalent? Meaning a man-portable weapon with an obscene rate of fire and the ability to carry enough ammo for more than just a few seconds of fire

If all you care about is RoF, than the MG42 would be the way to go. It's the fastest GPMG in a serious calibre, the original pattern ran as fast as RoF 25!. In GURPS, this gives you quite the edge, due to the way the Rapid Fire bonus breaks are set up (p. B373). In real life, almost all users thought this wasn't worth it, and regulated the gun down to RoF 20!.

A portable multibarrel gun just isn't worth it, cause the weight of the extra barrels, not to speak about the batteries, do nothing but to reduce your ammo load. And the increased barrel life never comes into play since you can't carry the ammo to begin with ...

Cheers

HANS

[The Colonel]

Presumably once we get to battlesuit infantry, a "man portable" minigun may become a thing, but then that's stretching the scope of the question. And it's probably just a minigun at that point anyway.

[Varyon]

Originally Posted by HANS

A portable multibarrel gun just isn't worth it, cause the weight of the extra barrels, not to speak about the batteries, do nothing but to reduce your ammo load. And the increased barrel life never comes into play since you can't carry the ammo to begin with ...

I kind of wonder if, at this point, replacing the extra barrels and rotating mechanism (but not the power supply, you'll still need that) with some sort of active cooling system might work out to be lighter than a Gatling-style gun for the same overall rate of overheating - or if this might be the case at TL 9. Perhaps not by enough to justify replacing the Gatling weapons already in use, but if you're developing a brand-new weapon system with ridiculous RoF, that might be the path to go. The barrel itself probably won't last as long, as every bullet is going through it rather than 1-in-6 or so, meaning you'll need a steadier supply of replacement barrels (although I wouldn't expect needing a huge supply of such), but for purposes of maintaining a high RoF, that should have you covered. Combine it with the newer polymer-cased cartridges (which result in the weapon heating up at something like 80% of the normal rate).

[Anthony]

Originally Posted by Varyon

I kind of wonder if, at this point, replacing the extra barrels and rotating mechanism (but not the power supply, you'll still need that) with some sort of active cooling system might work out to be lighter than a Gatling-style gun

Consumable coolants, in the form of water-cooled GPMGs, used to be a thing, but went out of favor for reasons that don't seem likely to change. A recycled coolant is an option but adds an awful lot of complexity.

[Ulzgoroth]

Originally Posted by HANS

No. If you want them to be, I wrote one up in High-Tech, p. 136, cause of course I get it, they look cool.

The GE Microgun (AKA XM214 6Pak) was never a viable contender, as it, too, was never intended to be manportable. Since it couldn't do anything its larger cousin, the Minigun, could but fired a weaker cartridge, it rightfully never entered production and nobody bought it.

How do you figure it wasn't intended to be manportable? The 6Pak configuration was specifically depicted deployed on infantry tripods in promotional material unless sources are actively fabricating evidence for some reason.

AFAICT it was never intended to be fired hand-held, rather than set up on a tripod. And it doesn't look like the ergonomics of doing so would be at all practical even ignoring the weight and recoil problems.

[Anthony]

Oh, I mentioned up-thread having seen some stuff about a supposed XM556 minigun. Having examined videos in slow motion...I suspect it's a single barrel automatic weapon with extra barrels as props.

[Rupert]

Originally Posted by Anthony

Consumable coolants, in the form of water-cooled GPMGs, used to be a thing, but went out of favor for reasons that don't seem likely to change. A recycled coolant is an option but adds an awful lot of complexity.

I don't think a water jacket and condenser is particularly complex. Heavy, though.

[DouglasCole]

Originally Posted by Pursuivant

Which makes me wonder whether the weapon harness described in Ultra-Tech might have real world applications, if only as a prop.

Steadi-cam harness?

https://i.ytimg.com/vi/qp4MBKZh-IU/maxresdefault.jpg

[Varyon]

Originally Posted by Anthony

Consumable coolants, in the form of water-cooled GPMGs, used to be a thing, but went out of favor for reasons that don't seem likely to change. A recycled coolant is an option but adds an awful lot of complexity.

Recycled coolant was what I was thinking. Specifically, you have the coolant circulating between the barrel and a dedicated heat pump that forcibly dumps the heat into the environment. The radiators are probably going to light up on IR, but then I don't think you can really expect to fire something at RoF 30+ for several seconds and maintain stealth anyway. But I may be overestimating how far heat pumps have come - and/or significantly underestimating how difficult they may be to ruggedize - and using rotating barrels really is the way to go.