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[3_14159]

Why not just use a 37mm gun that's uses smokeless powder.

There's no special reasoning for us to design a 40mm autocannon instead of a 37mm one. My original proposal came from a) looking at the Bofors 40mm cannon and the (more time-appropriate 2-pounder, and b) 40mm being a nice, round number.
(I also just noticed that the 1-pounder apparently used blackpowder).


And yes, I do expect we'll be mostly unable (or unwilling) to mount this 40mm quick-firing gun on a tank. There are several examples of 40mm-autocannon tanks from WW2, but only in an AA configuration; the Nimród,  the Möbelwagen and the M19 as a main examples. All of them are having open or lightly armoured turrets; they're all almost 20 tons of weight. And, most importantly, they're all WW2 designs.
We actually have an example of similar weapons mounted on a tank and as an auto-cannon: Ordnance QF 2-pounder and the QF 2-pounder naval gun. In comparison, the naval cannon is longer, far faster firing, and, well, an auto-cannon. Sadly, I cannot find the weight of the actual cannon for the AT gun. Judging from the relative weights of the German PAK 36 (450kg) and the vehicle-mounted KwK 36 (apparently about 215kg), both 2-pounders seem to be roughly the same weight.


But, finally, remember that we're talking about WW1 tanks, not WW2 tanks.
And, finally finally, I just remembered something: If we design the 40mm cannon and the tank concurrently, we probably won't be able to mount them on our design anyways. In this case, we're restricted to the machine gun or the 37mm blackpowder cannon for now.

[Slick]

An making the main gun an autocannon would give the design horrible tank to tank fighting capabilities.

Edit:
Hang on might as well post one such Deviantart thing I was talking about:
Part 1
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Cover-525443565
Part 2
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-I-525467838
Part 3
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-II-525487876
Part 4
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-III-525638811
Part 5
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-IV-527212856
Part 6
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-V-527311338
Part 7
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-VI-527424301
Part 8
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-VII-528256272
Part 9
http://wingsofwrath.deviantart.com/art/FNG-Fortified-Line-Plate-VIII-528264734

These pictures as well as their descriptions are quite insightful.

[somemildmanneredidiot]

Counter point to the mounting restriction: We should be able to design the basis of the turret based on rough size and weight using the 37mm with additional weight added onto it for testing if we are unable to use prototype 40mms for testing. Once the main work for the tank system is in place, it shouldn't be particularly difficult to adapt for the 40mm cannon.

An making the main gun an autocannon would give the design horrible tank to tank fighting capabilities.

Is there any particular reason why? A barrage of 40mm seems conceptionally more effective than a smaller amount.

Worst case scenario is that the problem is found in testing and we end up adapting a quick fire system or even a breech loading system for the job.

[Slick]

Listen I'll go deeper into this if necessary but gist of this-at least the best way I can put right now- is that autocannon have to use smaller...propellant charges while normal cannons can use larger.

For example heres the size of a shell for the M1 I posted earlier:
37×223mmSR

Here's the M3:
37x223R

Similar no?

[Aseaheru]

 A note that one of those tanks linked earlier serving as SPAA was designed to be used as a tank destroyer. It was taken out of that role due to not being able to do much to KV-1s, which panzer 3s and 4s had difficulties with all through the war.

 Also, on designing stuff used that turn by something else, If I made you wait between designing stuff used in others than your guns would take two years to develop with new ammo.

-edit-

 Saying that autocannons have to use smaller shells  (which is not necessarily true) actually works against your point here.

[Slick]

Not shells propellant charges.

The M1 and the M3-give or take-use the same shell size but one is simply better at anti tank then the other and
second what SPAA was linked that was originally anti tank.

Edit:
So the Nimrod...doesn't that support what I was saying considering it failed at the AT role?

[Aseaheru]

Right, found some examples of shell size for 35mm autocannons and the Bofors.

Oerlikon 35mm autocannon
-35×228mm

Bofors 40mm cannon
-L/60 40×311mmR (1.57 in)
-L/70 40×364mmR

Now, to try to find out how long the bullet is...

-edit-

Amazingly enough, found some data on that quickly.

 The British AA form of the 40mm bofors(which was mounted on a number of SPAA vehicles during WW2) was just under 18" long, with between 5.13" and 6.8" of that being projectile, depending on type of round.


 Also, on the M3 lee, the hull mounted gun was a 75mm howitzer. The tanks 37mm gun was in a standard turret up top.

[Slick]

Wait 35mm...all the guns I've seen in that caliber are late Cold war or are straight up modern.
Scratch that all the ones I've found-so far-are modern.

Edit:
Also I've seen 75mm autocannons but they've only been mounted on planes.

Actually I'm not even sure if it was an autocannon.

I've yet seen anything concrete saying it was.

Edit again:
The M3 Lee's 75mm wasn't a howitzer.
Heres the wiki page I guess:
https://en.wikipedia.org/wiki/75_mm_Gun_M2/M3/M6

Said gun was considered it's main armament not it's 37mm.

[somemildmanneredidiot]

So what you're saying is that due to how they were designed, the munitions for autocannons tended to have a smaller propellant charges, which meant that the shells had a slower muzzle velocity, which meant that they tended to do less damage.

Can you provide evidence of that as I haven't read anything about that during my reading about autocannons? I'm unsure of any problems that might occur due to propellant charges.

@The SPAA: I believe the point Aseaheru was making was that it was removed from that role because of a tank that more heavily armed tanks had difficulty damaging.

What this is all telling me is that the 40mm autocannon with two angled HMGs (or a front facing and rear facing, or whatevet configuration we decide on) will do quite well in an anti-infantry role/supporting role once the Monarchy develops armor thick enough for our 40mm AP munitions to be ineffective against.

The FNG series is interesting but I think our primary issue is advancing and holding the ground we've taken rather than keeping the Monarchy from overwhelming us, unless I misunderstand the point of the pictures. I'm on mobile so any text underneath the pictures is something I'm unable to access.

My thinking for the probable reason why autocannons were used for AA roles rather than AT or ground based is due to ammo and resource conservation as well as complexity. If you only need 3-5 shells for an engagement then being able to fire out 100-300~ shells in that time period isn't likely to be all that necessary, especially when the gun has more moving parts that might break down or go wrong as compared to a breech loading gun which can handle the same job just as well.

We're going for it because that level of munition deployment is exactly what we want to screw with the Monarchy and keep pushing them further and further back while we solidify our gains.

[Aseaheru]

 Right, its not a howitzer. Gaah, out old memories of reading it being called that! Out!

 Well, you also have most tanks being used as bunker busters or as infantry killers, which basically means many, many, many small bullets or big things full of HE. Compromise is the lesser option in that case, which is basically what an autocannon is.

 As for lower muzzle velocity, well, the final form of the Lee's 75mm cannon had a muzzle velocity of 618m/s, while the 40mm bofors went between 881 and 1021m/s, depending on version. The lee's mainly used armament(because really, that sponson thing was just icing on the 37mm cannon armed cake), meanwhile, had up to 884m/s of muzzle velocity

[Slick]

Wait what era of Bofors are we talking about.

Edit:
So has anyone read the Deviantart stuff I linked?

[Aseaheru]

L/60 and L/70. The L/60 being from 1934-... today and the L/70 showing up just after WW2.

[somemildmanneredidiot]

Hmmmmm. Well the point of the Landshark isn't because of its destructive prowess, but because of its intimidation power and ability to eat rifle rounds for breakfast. The 40mm cannon is really just to provide it with a more destructive option (that doesn't weigh 2,000kg) and to provide an immediate use for our 40mm cannon within the land war until we're able to have other uses for it. The ability to lob HE shells at enemy positions is just icing on the cake.

[Slick]

Wait would replacing the 37mm on are ships really be as simple slapping the 40mm in it's mount?

Edit:
Is Landshark the name we're going with?

Edit again:
Hey Aseaheru is there a Geneva Conventions or International Committee of the Red Cross (ICRC)
equivalent/s in this world? Cause me and my brother along with the infantry stuff are putting down medic/medical
ideas an some information would be appreciated.

[Aseaheru]

 There would have to be a bit of design work, but if I understand the proposed actions then there will be work done on the ship anyways.