1920s Colt 37mm Auto Cannon

I’m trying to track down some 37mm guns and ammo used in the US experimental T1 Cunningham light tank programme of the 1920s. The helpful experts on TankNet tracked down the following for me:

[quote]The T1 as “first demonstrated” had a mock up turret and gun.
That was replaced with a manufactured turret with an M1916 37mm and a .30 caliber MG.
Following testing, the chassis was converted to the Light Cargo Carrier T1.
Four T1E1 Light Tanks and two T1E1 Light Cargo Carriers were next contracted for with Cunningham.
Next was one T1E2 with the Browning 37mm semi-automatic gun, but it was later changed to the M1916 37mm.
The one T1E3 used the 37mm Browning, possibly the same as previously in the T1E2.
T1E4 was a rebuilt T1E1, equipped with the 37mm semiautomatic, which was standardized as the M1924.[/quote]

To complicate matters somewhat, another source observed:

[quote]Judging from the pix in “The Fighting Tanks” a 1933 book (WE reprint in 1969) by Jones, Rarey, and Icks, the Browning 37mm had a long barrel and the M1924 37mm had a much shorter barrel.

Hawkinson’s invaluable lists include entries for the Colt Model E1 and E2 Auto Guns with intermediate case lengths of 124-127mm (the E2 also being labelled “M1924”). Does the “M” designation mean that it was officially adopted for service?

So, the M1924 seems pinned down but unless this was the “long barrelled gun” and the photos mentioned above have the wrong captions, there is still some mystery.

Can anyone add any information, and especially the shell weight and muzzle velocity of the 37x124-127R ammo?