USA 37mm American Armament Corporation

[Vasco Da Gama]

There are some things you just do not expect to find in the UK. Pictured are 2 cases which turned up recently which I have very little information about. The markings on the base are very clear, American Armament Corporation, SA Gun ( I take this to be semi-automatic). From the markings on the primer I suspect a date of 1942, which is late for my understanding. The only reference I can find is for a developmental aircraft gun in the 1930s. Case length is 203mm, Rim 54mm and mouth 37mm. The very slight groove above the rim is 6mm high. They do look very much like the French Tube-Cannon (37x200) but the rim is smaller, 54mm rather than 57.5mm. The groove above the rim is a likeness of the USA 37mm M17 antiaircraft cases 223SR, but they have a smaller rim 51.1mm. I would be very glad if anybody could educate me as to what project these cases came from.

 

[M8owner]

I have attached the link to some past conversations on this topic:

http://www.bocn.co.uk/vbforum/threads/89927-37mm-American-Armament?highlight=american+armaments

 

[Vasco Da Gama]

As usual, ask BOCN and you get quality answers! It would appear the 203mm case length would be for the anti-aircraft gun made by AAC for export customers. The anti-tank gun and aircraft gun cases are apparently shorter.

 

[Tony Williams]

This is what I have on them - from my next book! :tinysmile_classes_t

37 mm AAC series

AAC (the American Armaments Corporation) was a controversial organisation which attracted a lot of publicity (not all of it good) in the 1930s. They proposed a wide range of different guns and ammunition for various roles, including aircraft and AFV armament, all in 37 mm calibre. None of these was adopted by the USA or any other major army, but a few of them saw service in obscure corners of the world. The four below are the known ammunition variations:

· 37 x 87R (Type M aircraft): 500 g HE at 380 m/s
· 37 x 142R (M2)
· 37 x 178R (For Dutch Marmon-Herrington AFV)
· 37 x 202R (Type F AA/aircraft?): 500 g HE at 610 m/s (L/40 barrel) or 820 m/s (L/50 barrel)

Slightly different ammunition was specified for an Automatic Naval Gun: a 570 g HE shell fired at 732 m/s. Case and gun dimensions are not known.

If anyone knows more, please post it!

 

[Tony Williams]

Thanks to Steve for sending me some interesting reading matter!

Two problems with AAC information is that there does not seem to be any document dealing with the guns and ammunition together, so it is not always clear which round goes with which gun; similarly, it is not always clear which ballistics go with each round. The information I posted above was the best I could put together, but there are inconsistencies: on reflection, I think that the attribution of a 610 m/s MV with the 37 x 203R case is probably incorrect (it was what the AAC catalogue said, but frankly I don't trust anything they say...); it seems far more likely that the 610 m/s MV fits either the 37 x 178R or the even the 37 x 142R.

Does anyone have examples of all four of the rounds? Is imaokie2000 still around? I would be very grateful for a hi-res photo of complete rounds for all four case lengths together in one pic (against a white background) for the new book... :wink:

 

[M8owner]

The discussion of this topic is quite timely. Look what I found in a magic box today. They appear to be training HE rounds with tracers. I cannot find any markings on them. If you desire one, let's work out a trade. Money is good too.

 

[Tony Williams]

Nice find!

A further update: as far as I can see from the rather unhelpful AAC catalogue, only two of the four 37 mm AAC cartridges were used in automatic weapons: the smallest (37 x 87R) and largest (37 x 203R). The Rapid Fire Gun which used the 37 x 142R ammo was certainly manually-loaded, and the Anti-Tank Gun (also associated with the Marmon-Herrington AFV) in 37 x 178R probably was, but I have not found any other information about this gun or its ammo.

The 37 x 87R was, as I posted above, used in an automatic gun which was the first model to emerge, being tested in 1934 (the company was only founded in 1933). The gun was known as the Type M as an aircraft gun (in a turret), and on a wheeled mounting was known as the Automatic or Mountain Infantry Gun. It was also (I think) fitted to AAC's experimental 10-wheel Combat Car (judging by appearances).

The 37 x 203R was used in the Type F (fixed) aircraft gun, the Automatic Anti-Aircraft Gun and the Automatic Naval Gun (my conclusions about these differing slightly from those of Fred Butt as expressed in his 2005 IAA article). These guns were not all the same: the Automatic AA gun and the Type F aircraft gun had the recoil spring wrapped around the barrel (like the Type M) but the Automatic Naval Gun had the recoil cylinder under the barrel.

Any comments or additional information welcomed...

 

[greif]

Both the Dutch colonial army (KNIL) and the Dutch Navy were using the AAC semi-auto guns on their boats. They were listed as 37 x 202R. One gun survived and is in depot.

 

[Tony Williams]

Thanks for posting these!

It seems they guns shown are the standard AA and aircraft guns in this calibre, with the recoil spring wrapped around the barrel. The "automatic naval gun" from AAC had a different layout (although almost certainly used the same ammo).

 

[M8owner]

The tips of these training HE rounds are made from aluminum or magnesium as they have white powder corrosion. A magnet will not stick to the tip.

 

[Tony Williams]

I'm feeling rather chuffed at the moment as I have made a discovery. Chinn commented that the smallest of the AAC cannon, in 37 x 87R calibre, was a straight copy of the Puteaux cannon being worked on by France and the USA at the end of WW1. Which means it was closely related to the Baldwin cannon, another US knock-off of the Puteaux.

However, Chinn doesn't mention the larger cannon. This got me wondering about the odd AAC Automatic Naval Gun which does not look like the others from AAC, so I did some digging in my photo files and discovered that it is a precise copy of the McClean automatic cannon developed before WW1, and sold only to the Russians! A few of these McClean guns survive, one of them in the Heugh Battery Museum in NE England (well worth a visit if you're in the area). I've attached the photo I took of this gun about 10 years ago.

 

[Tony Williams]

Some further thoughts on the AAC version of the McClean cannon:

The McClean was chambered for the 37 x 136R (USN 1 pdr Mk 6) which had rim and body diameters of 46.5 mm and 40.7 mm respectively: the AAC 37 x 142R measured 44.7 mm and 40.5 mm. In other words, rechambering the McClean for AAC's round would be a minor matter (AAC liked to have their own unique ammo, to ensure that any purchasers of their guns had to buy their ammo). AAC claimed their "Rapid Fire" 37 x 142R round fired a 570 g projectile at 610 m/s, whereas their "Automatic Naval Gun" (McClean) fired a 570 g shell at 732 m/s. OTOH, the Rapid Fire gun had a 40-cal barrel, the Naval gun a 50-cal, which might account for the difference.

So, I would tentatively say that AAC simply modified the McClean gun by rechambering it for their own 37 x 142R ammo.

Any more info or thoughts welcomed...

 

[highlandotter]

thanks for this fine photo Best that I have seen of this wandering gun from US to Russia to Spain.