Forgotten US WWII Mortars

[US-Subs]

I was recently asked to send some photos to a friend, and as long as I had them out I giured I'd go ahead and post them, with a little of the history behind them.

The US went through significant mortar development during WWII, today everyone remains very familiar with the 60mm, the 81mm and the 4.2-inch. What has been largely forgotten, however, is the US 105mm, 155mm, 250mm and 914mm mortars.

As the US began fighting the Japanese in the Pacific, we rapidly discovered that much heavier mortars were needed to deal with the caves and fortifications being used by the enemy forces. The result was the new series of heavy mortars. As far as I have been able to find, all but the 914mm were deployed in the Pacific, the 914mm was reportedly ready to go for the invasion of the Japanese mainland. There are also indications that the 155mm at least was deployed to Europe, I saw one of the mortars in an EOD training collection - I believe it was at Shrivingham - in around 1998.

I have three examples of these projectiles in my collection, a 105mm and two different models of 155mm. Nearly all of the series take the M4 rocket fuze, which did not require spin to arm, but one of my 155mm takes a smaller fuze, which I suspect would have been the M77 or something similar

 

[US-Subs]

In 30 years I have only seen two of the 250mm, one in the Picatinny collection and one in the Aberdeen collection. The Picatinny Museum no longer exists so the two should be at Aberdeen, but there were some indications the collection was pilfered when it was moved, so that is unsure.

To the best of my knowledge the 914mm only exists at Aberdeen Proving Ground. The entire assembly is on display, along with two models of projectiles.

 

[US-Subs]

There are very few references remaining to this series of mortars, one of the best is "Weapons of WWII" by GM Barnes. A fantastic book, describes all but the 250 which was somehow overlooked. The 250 is shown in another document (don't have it with me) where it was described as a 9.45 - inaccurate both in conversion from the metric and in confusion with the WWI mortar.

 

[US-Subs]

Last of the pages

 

[Chris]

Very nice items US-Sub and interesting information.
Specially the 914 mm mortar.
Why they called him Little David I can't understand.

I will drink a beer next week in Boletice on your healt

Chris
:beer::beer:

 

[US-Subs]

Thanks Chris, wish I were going with you - JO

 

[shelldude]

Fogotten U.S. WWII mortars

Hello JO,

THANKS for sharing your rare U.S. heavy mortar round collection with us. I had never seen an example of the 250mm before, it's a great reference photo. I've always been intrigued with the "Little David" behemoth.

Best regards,

Randall

 

[Ammotech]

would you have some tech info on the 105mm HE. seems that they found one in Churchill and according to the old Churchill records "that 105mm mortar trials were conducted here during the winters of 51-53"

 

[ordman]

I have drawings of a lot of the mortar round shown

 

[SG500]

"There were some indications the collection was pilfered"
I guess that's why the Little David projectile is still there, it would be a little difficult to pilfer.
Great rounds, great info, great collection, thanks for sharing with us.
Dave.

 

[Ammotech]

Any chances of sending them to me

 

[EOD]

I have drawings of a lot of the mortar round shown

Any chance you could upload these for us in the documet section?

 

[AMMOTECHXT]

Interesting thread, thanks for showing. I'm intrigued that the model numbers should begin with a `T' rather than M.

 

[BMG50]

Excellent thread, didn't know such a mortar existed that size. What was the range of Little David.

 

[US-Subs]

I'd have to look it up, but my source material is not a technical manual and may not be 100% correct. I'm commuting over 120 miles each way to work for the rest of the week and may not get a chance to check till this weekend, so if someone else has the info....

 

[HAZORD]

@AMMOTECHXT

Per your comment regarding the T numbers for some U.S. non-Navy ammunition, the U.S. has changed its mind a number of times regarding the designations of model numbers for it's ammunition. Prior to WWI, ammunition was identified by M and the year the design was adopted, so M1914 (similar to the German method of using the year). From WWI to July of 1925, ammo was given Mark numbers, abbreviated Mk. followed by a Roman numeral which was followed by an M number to designate a modification, so Mk. I M1. would be the first modification of the Mk. I item. After 1925 they have used the M number system for adopted models, and if modifications were incorporated the first mod would be A1. For preliminary ammunition that is being evaluated or tested, the U.S. started using T numbers (test). These are typically found on ammo dated from the 40's through the 60's. More recent preliminary design ammo is labeled with XM (experimental) numbers.

The U.S. Navy has been using the Mark and Mod system, so Mk. 66 Mod 5 would be the 5th modification of a Mk. 66 item. Understanding this, you can then unerstand how the Mk. 81-84 bombs were designed by the Navy at China Lake, whereas the M117 bomb, or BLU bombs are Air Force designs. Of course this is all changing, as I was told last Summer that the Air Force will be migrating to using all Navy bombs with the "crackle" thermal protective outer coating.