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StringWitch

Why didn't Japan ever make a quad 25mm?

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There were a number of twin and quad AA guns used in WWII, but the Japanese copy of the 25mm Hotchkiss seems an oddity in having a triple mount. The earlier 13.2mm had a quad mount, and one firing technique I've seen in contemporary footage of the triple 25mm is to fire off two barrels, then the remaining one during reload. It seems this would make a bit more sense with a consistent level of firepower from 4 barrels in total.

 

I can only imagine it was a practical restriction of how many people can be around the weapon to reload it, since there were to my knowledge two people per box, and with three barrels you can have a team in each usable cardinal direction around the weapon, well out of each other's way. Whereas other guns which did have quad versions were either fed with very long belts that weren't practical to reload anyway (2-Pounder) or were spaced well apart (quad Bofors was basically two separate twin units that rotate together). The quad 1.1"/75, which did have barrels together with small box magazines, ended up being replaced, and I wonder if it wasn't just its mechanical unreliability which removed it from service.

 

Any further thoughts?

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Another issue is that quad mounts require more horsepower to turn. Any manually powered mount would have to be able to be turned by Japanese sailors. Their small size was why the 5,500 ton CL's had 5.5" guns instead of 6" - their guns were manually loaded and the average Japanese sailor couldn't lift the 6" shell.

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The triple mount had enough problems, mostly with ammo loading and accuracy because of oscilations caused by the recoil of the other guns of the mount that were unsufficiently dampened. A quad mount would only make matters worse.

On 19/5/2018 at 4:47 PM, ColonelPete said:

That is the problem. Too many people needed.

As for the increase of the number of crew members, it would have been a couple of loaders more in worst case, so having like 100 people more in a crew of 2800 (for Yamato) wouldn't have been such an issue.

On 21/5/2018 at 3:53 AM, DarthDon49 said:

Another issue is that quad mounts require more horsepower to turn. Any manually powered mount would have to be able to be turned by Japanese sailors. Their small size was why the 5,500 ton CL's had 5.5" guns instead of 6" - their guns were manually loaded and the average Japanese sailor couldn't lift the 6" shell.

The added weight wouldn't have been an issue too because a quad mount wouldn't have had a weight much greater than that of a triple. Also, you can always make things easier by changing the gear ratio when talking about manual traverse, or even easier by choosing powered traverse, electrical or hydraulic.

 

A quad mount, even with most assets reworked, wouldn't have been much better than the infamous American 1.1''/75 quad, know as the Chicago piano, that had a larger caliber and was clip fed. ~1'' caliber AA guns were unsufficient even at the begining of the war, so there was no need to even try to make a quad 25mm when even the triple was way behind the double boffors, that had a similar weight. The Japanese simply had to make a new gun, not a quad mount of an existing bad-performing gun.

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That was not about the ships crew. That was about people having to move around the gun mount.

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5 hours ago, ColonelPete said:

That was not about the ships crew. That was about people having to move around the gun mount.

The Chicago pianos did not actualy had this problem, and it was not an issue for the triple mount too so I do not think this would have been a problem in the quad too, because there would have been more space behind the guns. In the triple mount they had 6 people in 2 rows, so in the quad it would have been 8 in 2 rows, 2 behind each gun in both cases. Of course a quad mount would require more space on the deck, but not much more than the triple.

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More people would of gotten mowed down by usn fighter strafes lel

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On ‎6‎/‎17‎/‎2018 at 6:43 PM, GeorgeT1012_gt said:

The added weight wouldn't have been an issue too because a quad mount wouldn't have had a weight much greater than that of a triple. Also, you can always make things easier by changing the gear ratio when talking about manual traverse, or even easier by choosing powered traverse, electrical or hydraulic.

 

Not entirely true. Yes, one can make the mount turn by changing the gearing, but, as many navies discovered, not fast enough to track a fast-moving modern (for the time), plane. As for powered mounts, many navies, the IJN included, tried them but had problems with reliability during combat as well as with supplying power to mounts added to an older ship.

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