Machine Guns and Cannons (Ground, Vehicle, and Aircraft Mounted Weapons)

[Weaver]

The main problem with attempting to retrofit modern, larger calibre weapons onto smaller, older platforms is that the modern, larger calibre weapons (>=40mm) require substantial below decks ammunition handling equipment and storage in order to gain the advantages you're seeking in higher rates of fire.  Smaller calibre weapons have much smaller needs for such things - although even their power consumptions are substantially higher than the older weapons they replace so there would be a need to considerably increase power generation, not only for the weapons and their mounts but also their handling machinery and electronics to run the whole lot.

Right in general, but not always true. The 76/62 series immediate below-decks fitting is basically a 1-deck high cylinder of about the same diameter as the turret itself, and it can and has been fitted above the weather deck on a compact cylindrical or square deckhouse, in the same way as the Fast Forty. If you want more ammo capacity to feed to it manually from a separate magazine, that's another matter, of course. The earlier 76mm was mounted on very slim pedestals above the weather deck:



The feed system could be anywhere from 2.5m to 11m long....

Note that I'm not suggesting replacing all the 40mm on a one-for-one basis, just that a useful 76mm fit might be possible.


Electronics is the big killer (again) and you can see this in many postwar conversions where torpedo tubes were sacrificed for deckhouses holding radar "offices". The equipment, particularly 50's/60's analogue equipment, needs substantial power supplies and in many cases chilled water for cooling too (I understand that chilled water supply for the Ikara's radar tracker was THE major headache for it's maintainers).

I'd be very surprised to find many WWII era ships still around today, though.   Most would have been replaced by the 1970s when their machinery and hulls were worn out.  Even the US Navy with its substantial wealth was finding it difficult to maintain its WWII era DDs in service by the 1960s and was looking for the substantial number of hulls required to replace them.

Very true, but unless I've read him wrong, my understanding is that icchan's scenario is late 1960s...

There were STILL a few Fletchers, Gearings and Sumners out there in small navies until the end of the century. My 2002 Jane's lists 15 Gearings, 1 Fletcher and 2 Cannons, although it might be a little out of date since the S.Korean Gearings seem to have been decomissioned in about 2000. Interesting in the context of this debate is that most of the Gearings have sacrificed one or two 5" turrets (B-turret is favorite) and have a variety of Fast Fortys, 76/62 Compacts and Bofors SAK-57s:



(Mexican Netzahualcoyotl)

[Weaver]

Well, the way things are going for this fictional military and whiffery, there's a preference to the higher caliber rounds.  I thought about it, and realized that you can hit with a lot of small rounds, but the vital bits that would be affected aren't that large - and neither is the pop of the 20mm shell.  It has to hit very close, while the 30mm can be further away from the particular vital spots and still hit them.  It makes the "kill area" of the target larger, so there's an advantage to the bigger shell.  That may explain the mean-rounds-to-kill variation.

So I'm all for the 35s, as they're "only slightly smaller" than the 40s they replace and yet are still explosively happy.  And I can only imagine the pain you could cause with them to a small attack boat that strayed too close...

Another option might be to upgrade the 40mm Bofors weapons. Breda did good business for years making automatic feed systems for them that sat on top of the gun without changing it's mounting characteristics. For instance, the Type 64 was an open-topped twin with 100 rounds per barrel and the Type 564 was a single with 144 rounds. Bofors have developed a 90-round magazine primarily for their advanced Trinity CIWS system, but it can also be re-fitted to older guns. All these guns have RPC as an option.

The main argument for the bigger calibres is range: the further out you can start the engagement, the more time you've got to score a hit or correct your fire.

Another important threshold is where the technology of the day makes proximity fuses available. The argument goes that a bigger gun firing proximity-fused frag rounds covers a bigger area of sky with lethal projectiles than a small gun firing contact-fused or solid rounds. This was the main reason for the late WWII move to 76mm and it forms part of the argument, late 1970s onwards, for the Fast Forty. Fusing is particularly difficult against a sea skimmer though, since the closing rate is high, the target signature is small and the sea is close, which is why it took digital technology to make a smart proximity fuse as small as 40mm. The wheel has now turned full circle with the 35mm AHEAD ammo which is basically a very precise time fuse with smart, fast-reacting fuse-setting at the muzzle (that's WAY beyond 1960s tech though).

If you really want small calibre, then there were a variety of Sea Vulcan mountings that carried the 20mm Vulcan in a "conventional" mounting far less sophisticated than Phallanx.

[icchan]

Wow, some great info!     Very strongly inspiring me to work with the 40mm system...

Yeah, the rough timeframe is 1975, so there should still be enough old classics running around.  Threat-wise, for anti-ship missiles I'm facing things like SM-1 Standards, Kh-22, and P-270 Moskits for (very) supersonic threats, everything else is a low-and-slow subsonic.  Deep envelopes for defense guns is going to help a lot in that regard, and like I said the caliber preference showed up even before things got discussed.

The Compact twin 40mm mount is probably what I'll end up with, since it seems the Fast Forty isn't old enough to have a sufficient deployment time.  Maybe as a contemporary "replacement program" which means I might have a few ships, and a few newer ships, with them but the majority seems to run the earlier Compacts.  Still, there's a lot to be said for the things, and the mixed-load HE and APFSDS puts a lot of potential into the use of the things on light tanks/heavy IFVs, for the ground service.

Some great data in this thread, thank you guys ALL.  Now to start poking ships...and deciding what I can get away with.

[dy031101]

The Youtube video of a truck-mounted BMP-1 turret reminds me of this...... a rather truck-like (and, IIRC, truck-based) 6 x 6 IFV designed by a private firm in Mainland China.



Granted, the Cubans armed some of their BTR-60 with it, too?

[rickshaw]

The main problem with attempting to retrofit modern, larger calibre weapons onto smaller, older platforms is that the modern, larger calibre weapons (>=40mm) require substantial below decks ammunition handling equipment and storage in order to gain the advantages you're seeking in higher rates of fire.  Smaller calibre weapons have much smaller needs for such things - although even their power consumptions are substantially higher than the older weapons they replace so there would be a need to considerably increase power generation, not only for the weapons and their mounts but also their handling machinery and electronics to run the whole lot.

Right in general, but not always true. The 76/62 series immediate below-decks fitting is basically a 1-deck high cylinder of about the same diameter as the turret itself, and it can and has been fitted above the weather deck on a compact cylindrical or square deckhouse, in the same way as the Fast Forty. If you want more ammo capacity to feed to it manually from a separate magazine, that's another matter, of course. The earlier 76mm was mounted on very slim pedestals above the weather deck:



The feed system could be anywhere from 2.5m to 11m long....

Note that I'm not suggesting replacing all the 40mm on a one-for-one basis, just that a useful 76mm fit might be possible.

See the tall, narrow hatch towards the base of that tower?  Thats the ammunition replenishment hatch.  I'd suggest that the below mount magazine is fairly limited in its capacity and that in turn would limit the amount of time an engagement could be sustained by such a  mounting.   While I agree its a solution but its a limited one.  Somewhere else on the ship, more rounds must be stored if your ship is going to have any sort of sustainable engagement capability.  I'd be concerned at what happens during a saturation attack.  Your below mount magazine would rapidly run out of ammunition and hence require replenishment.  Not always possible if any sort of sea is running and not something I'd like to be doing in the middle of an engagement.

Electronics is the big killer (again) and you can see this in many postwar conversions where torpedo tubes were sacrificed for deckhouses holding radar "offices". The equipment, particularly 50's/60's analogue equipment, needs substantial power supplies and in many cases chilled water for cooling too (I understand that chilled water supply for the Ikara's radar tracker was THE major headache for it's maintainers).

Well thats what happened when you used valves.   

Ikara was an interesting system.  Old Wombat might be able to supply more information.  In many ways it's a shame that development was handed over to the British who essentially killed the system trying to turn it into something it was never designed to be (a container launched ASW weapon).   In some ways much better than its competitors (Asroc and Malafon) in that it dropped its torp but flew one, thereby not alerting the submarine that a torpedo had been dropped in its vicinity as the other missiles did when the carrier fell into the sea at the same time as the torpedo.   Personally, I'd have liked to see it developed as an anti-shipping missile.  The Tourana drone version used a turbojet which would have been more efficient than rocket power alone and it could have carried a huge warhead.   As a first generation system it would have been ideal.

I'd be very surprised to find many WWII era ships still around today, though.   Most would have been replaced by the 1970s when their machinery and hulls were worn out.  Even the US Navy with its substantial wealth was finding it difficult to maintain its WWII era DDs in service by the 1960s and was looking for the substantial number of hulls required to replace them.

Very true, but unless I've read him wrong, my understanding is that icchan's scenario is late 1960s...
[/quote]

That didn't seem clear to me.

There were STILL a few Fletchers, Gearings and Sumners out there in small navies until the end of the century. My 2002 Jane's lists 15 Gearings, 1 Fletcher and 2 Cannons, although it might be a little out of date since the S.Korean Gearings seem to have been decomissioned in about 2000. Interesting in the context of this debate is that most of the Gearings have sacrificed one or two 5" turrets (B-turret is favorite) and have a variety of Fast Fortys, 76/62 Compacts and Bofors SAK-57s:



(Mexican Netzahualcoyotl)

I wonder how much time they actually spend at sea as against how much time they spend tied up?

I must admit I've become quite interested in the Bofors 57mm gun.  Looks like a good compromise between the 76mm and the 40mm ones.  Appears to have earnt a new lease on life as a consequence - gone from an "also run" of the family to actually quite a star performer.

[rickshaw]

If you really want small calibre, then there were a variety of Sea Vulcan mountings that carried the 20mm Vulcan in a "conventional" mounting far less sophisticated than Phallanx.

If you're not limited to Western equipment, the Soviet 30mm Gatling gun systems which seemed to sprout all over their ships during the 1970s are IMHO an excellent alternative.   If they could be coupled with a good Western fire control system, I suspect you'd be onto quite a winner.   

[icchan]

I'm not limiting much; this is all for an AU project and a fictional country/world.  Weapon systems are pretty much pilferable from any and all sides, simply under the "different manufacturers" rule.  Keeping within national preference (i.e. the rate-of-fire vs weight-of-shell debate) and keeping within doctrinal roles, and not just scattering...

...some of those Soviet 30mms indeed show promise and might be part of "near-term modernization plans."  And just to be WoG on the timeframe, it's no later than 1975.  Still, thank you all for the huge pile of help - that Compact 40mm twin mount might well just become THE definitive gun mount on everything I run for this navy.

Hm, one of those would look most spiff on the nose end of a Flower-class...

[Weaver]

Right in general, but not always true. The 76/62 series immediate below-decks fitting is basically a 1-deck high cylinder of about the same diameter as the turret itself, and it can and has been fitted above the weather deck on a compact cylindrical or square deckhouse, in the same way as the Fast Forty. If you want more ammo capacity to feed to it manually from a separate magazine, that's another matter, of course. The earlier 76mm was mounted on very slim pedestals above the weather deck:


The feed system could be anywhere from 2.5m to 11m long....

Note that I'm not suggesting replacing all the 40mm on a one-for-one basis, just that a useful 76mm fit might be possible.

See the tall, narrow hatch towards the base of that tower?  Thats the ammunition replenishment hatch.  I'd suggest that the below mount magazine is fairly limited in its capacity and that in turn would limit the amount of time an engagement could be sustained by such a  mounting.   While I agree its a solution but its a limited one.  Somewhere else on the ship, more rounds must be stored if your ship is going to have any sort of sustainable engagement capability. 

I actually said as much in my quote above. I don't know how the system works for the old mounting, but the 76.62 Compact has a "bottling factory" directly beneath it holding 80-odd rounds. At maximum rate, that's about 1 minute's supply, but that's a bit unrealistic: the mounting would probably shake itself to bits before it ran out of ammo! What the cyclic fire rate really represents is the number of rounds in a short burst followed by a correction.

I'd be concerned at what happens during a saturation attack. Your below mount magazine would rapidly run out of ammunition and hence require replenishment.  Not always possible if any sort of sea is running and not something I'd like to be doing in the middle of an engagement.

Like I say, I don't know how it works for the old mounting. The usual procedure with the 76/62 Compact is to start manually reloading the carousel as soon as it starts firing, which IS possible, and hope that it doesn't catch up with you. That's fairly common to rapid-fire auto-loading naval guns. Any of these beat the hell out of slapping clips in a Bofors or individual rounds in a 3" 50cal, given that engagements with jets or missiles tend to be measured in seconds rather than minutes.

It's a bit of a crappy choice either way, but I think I'd rather be inside a ship under attack lumping 3" rounds into the carousel than running around on deck handballing Seacats upto a launcher on the hanger roof. Ships in the Falklands routinely got their topsides sprayed with 20mm/30mm fire by the incoming jets, which doesn't seem terribly healthy when you're busy piling up 140lb fibreglass fireworks around the base of the director (yes, really )

Ikara was an interesting system.  Old Wombat might be able to supply more information.  In many ways it's a shame that development was handed over to the British who essentially killed the system trying to turn it into something it was never designed to be (a container launched ASW weapon).   In some ways much better than its competitors (Asroc and Malafon) in that it dropped its torp but flew one, thereby not alerting the submarine that a torpedo had been dropped in its vicinity as the other missiles did when the carrier fell into the sea at the same time as the torpedo.   Personally, I'd have liked to see it developed as an anti-shipping missile.  The Tourana drone version used a turbojet which would have been more efficient than rocket power alone and it could have carried a huge warhead.   As a first generation system it would have been ideal.

It also had more range than either ASROC or MALAFON, though of course, detection range is the limiting factor in ASW. I'm a big fan of the Ikara in principle, I just wish more effort had been put into updating it and (in the UK) actually fitting it: I don't buy the argument that a helo is a better option, it's just a different one, with different strengths and weaknesses. I also wish we'd just bought the Aussie system rather than trying to re-engineer it with a pointlessly precise hydraulic launcher and a totally different magazine system. Allegedly submariners knew when an Ikara Leander was about to fire because they could hear the hydraulic pumps fire up from miles away. Part of the problem was that a nuclear depth charge was intended (but never developed) for the UK version, which in turn imposed different storage/handing/positive control requirements.

I suspect that with later, integrated combat systems, it should be possible to do away with the Ikara tracker entirely, and just "borrow" a SAM/gun tracker that's been fitted with a command transmitter. Then again, by the time you get to the Exocet/Otomat era, inertial guidance with mid-course update becomes feasible, as MILAS demonstrates.

I'd be very surprised to find many WWII era ships still around today, though.   Most would have been replaced by the 1970s when their machinery and hulls were worn out.  Even the US Navy with its substantial wealth was finding it difficult to maintain its WWII era DDs in service by the 1960s and was looking for the substantial number of hulls required to replace them.

I must admit I've become quite interested in the Bofors 57mm gun.  Looks like a good compromise between the 76mm and the 40mm ones.  Appears to have earnt a new lease on life as a consequence - gone from an "also run" of the family to actually quite a star performer.

There's a fairly strong "burger war" between Bofors and OTO-Melara, with, for instance, OTO saying things like "superior to any 57mm weapon on the market" - ooh, wonder which one they mean (given that there's only one)? The usual argument for the 76mm is it's bigger HE shell for surface fire, but Bofors' response is to point out that their gun's higher RoF means you should be comparing a 76mm round to a 57mm burst and the latter will make a hell of a mess of a typical unarmoured modern ship.

[dy031101]

Something that came out of my incomplete attempt at a what-if navy...... although only the forward guns were salvaged from the WWII-vintage destroyer escort that it replaced (pintle-mounted cannons...... maybe, but the Oerlikons didn't seem to last as long as even the 3"/L50 or 5"/L38 DP has).

[rickshaw]

I actually said as much in my quote above. I don't know how the system works for the old mounting, but the 76.62 Compact has a "bottling factory" directly beneath it holding 80-odd rounds. At maximum rate, that's about 1 minute's supply, but that's a bit unrealistic: the mounting would probably shake itself to bits before it ran out of ammo! What the cyclic fire rate really represents is the number of rounds in a short burst followed by a correction.

Yes.  Sustained rates of fire are invariably much lower than maximum in such weapons.  However, I'd point out that in the case of the picture you used to illustrate, with the 76mm high on the tower, the only way to replenish the "bottling factory" is across the open decks, in the middle of an engagement - which is why I pointed out the ammunition handling hatch on the base of the tower.   Even you acknowledge the idea of handling ammunition across the decks leaves a great deal to be desired.

It's a bit of a crappy choice either way, but I think I'd rather be inside a ship under attack lumping 3" rounds into the carousel than running around on deck handballing Seacats upto a launcher on the hanger roof. Ships in the Falklands routinely got their topsides sprayed with 20mm/30mm fire by the incoming jets, which doesn't seem terribly healthy when you're busy piling up 140lb fibreglass fireworks around the base of the director (yes, really )

True.  Interesting though, that the Seacat was shown, despite its age to still be an effect missile in the Falklands/Malvinas conflict.   More I suspect because of its scare value than necessarily because it could hit anything easily.   FEARLESS IIRC managed to down one or two Argentine aircraft with it which was remarkable and is a tribute to the gunner manning the director IMHO.

It also had more range than either ASROC or MALAFON, though of course, detection range is the limiting factor in ASW. I'm a big fan of the Ikara in principle, I just wish more effort had been put into updating it and (in the UK) actually fitting it: I don't buy the argument that a helo is a better option, it's just a different one, with different strengths and weaknesses. I also wish we'd just bought the Aussie system rather than trying to re-engineer it with a pointlessly precise hydraulic launcher and a totally different magazine system. Allegedly submariners knew when an Ikara Leander was about to fire because they could hear the hydraulic pumps fire up from miles away. Part of the problem was that a nuclear depth charge was intended (but never developed) for the UK version, which in turn imposed different storage/handing/positive control requirements.

The RAN's launchers were IIRC electrical, rather than hydraulic but I'm willing to be corrected.  As to why would need to give it precise pointing, I have no idea as you'd only need to point it in the general direction before lighting the blue touch paper.  The guidance system should correct for any minor differences in heading which would be required.

The chief advantage of the helicopter I'd have thought was its utility - you can do many more things with one which you can't do with a missile.

I suspect that with later, integrated combat systems, it should be possible to do away with the Ikara tracker entirely, and just "borrow" a SAM/gun tracker that's been fitted with a command transmitter. Then again, by the time you get to the Exocet/Otomat era, inertial guidance with mid-course update becomes feasible, as MILAS demonstrates.

If the SAM/gun tracking radar could track the Ikara it would have been able to guide it.  Integrating it though, with the sonar system was more difficult.  Basically you had to be able to compare the two tracks and when they crossed, that was where the Ikara dropped its torpedo.

There's a fairly strong "burger war" between Bofors and OTO-Melara, with, for instance, OTO saying things like "superior to any 57mm weapon on the market" - ooh, wonder which one they mean (given that there's only one)? The usual argument for the 76mm is it's bigger HE shell for surface fire, but Bofors' response is to point out that their gun's higher RoF means you should be comparing a 76mm round to a 57mm burst and the latter will make a hell of a mess of a typical unarmoured modern ship.

Well, as a counter-argument you'd only need one or two 76mm rounds to do the same thing.   57mm though would be more useful in the counter-missile/AAA roles.  Higher ROFs always help there.

[dy031101]

As part of my attempt in butchering the Graf Spee Shipbucket picture, I'm thinking of replacing the 15cm anti-ship and 10cm AA guns with French-made 100mm/L55:



Does the 15cm mount have below-deck penetration?  If it does, is it enough to accommodate the French gun system?

[dy031101]

If you're not limited to Western equipment, the Soviet 30mm Gatling gun systems which seemed to sprout all over their ships during the 1970s are IMHO an excellent alternative.   If they could be coupled with a good Western fire control system, I suspect you'd be onto quite a winner.   

Curiosity: how do you think of the predecessor AK-230 twin 30mm?

[rickshaw]

If you're not limited to Western equipment, the Soviet 30mm Gatling gun systems which seemed to sprout all over their ships during the 1970s are IMHO an excellent alternative.   If they could be coupled with a good Western fire control system, I suspect you'd be onto quite a winner.   

Curiosity: how do you think of the predecessor AK-230 twin 30mm?

Revolver cannons tend to be much of a muchness really.  The AK-230 is the mounting.  The NN-30 is the cannon.   It appears from what I've found on the net to be an adequate weapon of its class.  The AK-630, its successor, has a considerably higher ROF.

[Maverick]

It seems the AK-630 is also available with a twin over/under mount.  A turret mounting 12 x 30mm barrels sounds quite imposing, but I shudder to think of the ammunition consumption alone!

Regards,

Mav

[dy031101]

It appears from what I've found on the net to be an adequate weapon of its class.  The AK-630, its successor, has a considerably higher ROF.

Would you therefore still recommend AK-630 or Phalanx over AK-230?

It helps me with a brainstorming session that I'm doing.