Load data for 16" guns?

Reloading equipment, methods, load data, powder and projectile information.

Load data for 16" guns?

Post by bladeracer » 20 Aug 2021, 7:52 pm

https://www.youtube.com/watch?v=-2oDJDgEGGU&t=587s
Interesting video about the powder charges used on US battleships, specifically the 16" 50-caliber (20,320mm barrel) guns. The specification I found said 20m "bore length", and 20.7m barrel length to breech face, neither of which works with a 50-caliber, 16" gun, or the shorter 45-caliber gun. Unless they actually jam the shell four-meters into the rifling, they're not going to fit 2.7m of powder charge behind it. I couldn't find a definitive length for the shells, but scaling a photo it looks to be roughly four times the diameter, or about 1.6m long, plus the 2.7m of powder bags, making the "cartridge" 4.3m long.
USS_Iowa_gun_loadb.jpg
USS_Iowa_gun_loadb.jpg (43.82 KiB) Viewed 1498 times


4,620,000gn charges were standard, but dropped to 4,585,000gn charges post-WW2. The 297kg charge column is 450mm diameter by 2700mm long!

During WW2 the barrels had a life of 290rds, the reduced charge extended it to 350rds. They eventually got it up to around 1500rds barrel life. The barrels are 25-caliber-twist, or 10.16m per revolution, equivalent to a 5.6"-twist .223Rem (8"-twist .223 is 35.7-caliber twist). 96-groove rifling, .150" deep.

Particularly interesting is the 5fps variation in velocity at 2425fps with the 1200kg AP shell (2615fps with the lighter 860kg HE shell) during WW2, just astonishing. And also that the powder deteriorated over 50+ years (it was originally manufactured in the 1930's), although I'm not sure he's explained it quite correctly. After more than 50 years, the powder deterioration increased the average ES from a WW2 ES of 5fps, up to a 32fps average ES, which becomes a problem in long-range accuracy. He seems to be explaining it purely as a loss in velocity, but it's actually a loss of accuracy due the increased variation in velocity. A difference of 32fps in muzzle-velocity at 1000m isn't much at all, but by 38km it's getting significant enough to risk unnecessary collateral damage.

Also interesting that they "hand-loaded" the powder bags to ensure the weights were correct due to variations in the sizes of the "grains" that were stacked into the bags. They basically filled the bag with a low charge, then "trickled" it up to weight by laying additional grains on top.

The only ballistic calculators I've found that allow ranges of 38km or more, all ignore air drag, and thus, BC entirely (BC is a drag "factor" so is irrelevant in vacuum). In a vacuum, a ballistic (unguided and unpowered) projectile (a bullet is a specific type of projectile) follows a parabolic trajectory, in air it follows a ballistic trajectory due to drag bleeding off the velocity. In space, the 16" gun would send its 1200kg shell out to 55.133km to 55.372km (240m spread due to 5fps variation in MV) fired at 45-degrees, on earth it is launched at around 40-degrees for a maximum range of 38km. Launched 16fps slower or faster would push it to 54.52km to 55.991km, a 1470m spread over the target. These numbers would be reduced due to drag (in the video he says it's roughly 500yds short/long), as with the maximum range, but I would expect drag would also decrease the accuracy anyway.
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Re: Load data for 16" guns?

Post by disco stu » 20 Aug 2021, 8:18 pm

I just got a new warship and was just about to go searching for this very info, cheers :D

Boy that barrel life is short. They must have carried a lot of barrels around with them
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Re: Load data for 16" guns?

Post by in2anity » 20 Aug 2021, 8:43 pm

Do love me a carbine ;) ;)
At what point does lack of maintenance become patina?
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Re: Load data for 16" guns?

Post by animalpest » 20 Aug 2021, 8:55 pm

Wow now's that some info and stats I never knew. Thank you
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Re: Load data for 16" guns?

Post by pomemax » 20 Aug 2021, 9:23 pm

Any good for rabbits
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Re: Load data for 16" guns?

Post by bladeracer » 21 Aug 2021, 10:00 am

pomemax wrote:Any good for rabbits


Head shots with the AP shell, the HE not so good :-)
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Re: Load data for 16" guns?

Post by pomemax » 21 Aug 2021, 2:40 pm

good video just watched ,interesting on barrel life can understand why they went to missile carriers now .
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Re: Load data for 16" guns?

Post by bladeracer » 21 Aug 2021, 3:49 pm

pomemax wrote:good video just watched ,interesting on barrel life can understand why they went to missile carriers now .


Just like tanks, smoothbores are the way to go nowadays, they last longer and are more versatile than shells.

Considering the barrels are 110-tons each and more than 20m long, I'm sure they never tried replacing one at sea, changing them in the field is a little more involved than the Ruger 10/22 :-)

The Iowa-class BB's carried 130 shells per gun, so 1170 shells. I don't know what ratio of AP to HE they carried but, if we assume 25% AP (for hardened targets as ships hardly ever engaged each other after WW2) then they had 350 tons of AP shells, 755 tons of HE shells, and 350 tons of propellant on-board. I can't even guess how much room that lot takes up in the bowels of the ship. Each shell with bags takes up about 2m3 without any racking, so a minimum of 2,264m3 of volume. Stacked four-meters high it would cover 565m2 of floor space, more than a quarter-acre. The bags were man-portable (50kg apiece) so would be more compact to store than the shells.

In comparison, the 32 Tomahawks Iowa carried were only 520mm diameter, 6.25m long complete, and weighed 1300kg or 1600kg. Virtually the equivalent of two complete shells, but with enormous range and much better accuracy against ground targets. For anti-ship capability she carried 16 Harpoons, each only 340mm diameter, 691kg, and 4.6m long, with four-times the range and far greater accuracy. I know the Harpoons were carried "ready for launch", and I think the Tomahawks were also, so none of the loading rigmarole required.

In 2016 they were dismantling the remaining 15,595 16" shells left in stores, so you'll have to make your own ammo if you decide to buy one :-)
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