QuintusO said:

175gr M1 Ball is the round the M1 was designed for. Where are you hearing it didn't work well in it?

The same HWS (Hackley, Woodin and Scranton: History of Modern U.S. Military Small Arms Ammunition, Vol 1, page 116): 

By 1936 a few of the new M1 rifles were being tested and used by the service, and some complaints were received of malfunctions when firing the M1 ammunition.....

In March 1939, the Infantry Centre at Camp Benning, Georgia, stated that the M2 ball cartridge greatly improved the performance of the M1 rifle, except that it gave greater smoke when fired. The same month the M2 was approved for general use for all non-belt-fed weapons.....

On January 12 1940, the M2 replaced the M1 ball as standard for all Cal. .30 weapons, except aircraft machine guns and Navy issue.

I don't know what the Army were thinking of when they chose the bullet design for the T65 et seq. Did they have better ranges by then (presumably WW2 would have led to the opening of more practice ranges) in which case a long range wouldn't have been an issue?

I stand corrected. Interesting, since I've read HWS I many times and don't remember reading that. Thank you for the citation.

autogun said:

I don't know what the Army were thinking of when they chose the bullet design for the T65 et seq. Did they have better ranges by then (presumably WW2 would have led to the opening of more practice ranges) in which case a long range wouldn't have been an issue?

I'm gonna be honest I think it was "being expeditious" which is another way to say "laziness".

EmericD said:

They reverted to the Mle1906 shape for the .30 M2 excatly because the M1 had too much range, and not enough drag...

Huh???

I think that was the French slipping through a bit.

What Emeric wrote is exactly what U.S. sources (like Hatcher's Notebook p. 23ff) say. 

What is your view why the M1 was dropped and the M1906 (under the new name M2) re-introduced? 

graylion said:

EmericD said: They reverted to the Mle1906 shape for the .30 M2 excatly because the M1 had too much range, and not enough drag... Huh???

I've already dealt with this in posts 49 and 51 in this thread.

The "complete" story as told by Col. Hatcher:

At this time we had on hand about two billion of the war-time .30-'06 cartridges, and as ammunition is perishable, the policy was to use up the oldest ammunition first, keeping the newer for war reserve.
Thus the shooters on Army, National Guard and Civilian rifle ranges had to use the old war time stuff, while wishing for the happy day to come when they could get some of the good new ammunition [the M1] to use.
Finally about 1936 that wished-for day arrived, and with it trouble of an unexpected sort. The new ammunition had so much longer range and carrying power that it began to shout beyond the
previous danger zones of the existing ranges. The National Guard Bureau then requested the War Department to make up some ammunition like the old 1906, to use on the restricted ranges, and the order was given to make up 10,000,000 rounds of it.
This short range ammunition was made as much like the 1906 as possible. It had a 150 grain flat base bullet, but the jacket was of course made of gilding metal instead of the old cupro-nickel. It was,
however, colored to look like the 1906 by the use of a stannic stain, so it could be de distinguished from the M 1. The ogive was of the same shape as the M 1, and differed a bit from the shape of the 1906, but the difference was so slight as to be imperceptible.
Some of this ammunition reached the Service Boards. which by now had lost all of the old World War I machine gunners who so keenly felt the inadequacy of our ammunition in 1918. Our soldiers liked the lessened recoil of the new ammunition. More rounds could be carried for the same weight, etc., so the suggestion was made and carried through that it should be substituted for the M 1. In 1940 this ammunition with some slight further changes, was standardized as Cartridge, Ball, Caliber .30 M 2.

Remember that Gal. MacArthur rejected the choice of the .276 Pedersen for the Garand M1 because of the existing stock of .30-06 Mle1906 ammo, a stock that was already depleted by the time the Garand M1 was standardized in 1936...

M2 is not the same thing as M1906. The only thing they share in common is the projectile shape and lead core. Everything else is different.

The MacArthur story is a little oversimplified. He carried over the recommendation of the Ordnance Board, which was convinced by the existence of the ZH-29 and T1 Garand that a .30 caliber selfloading rifle light enough to meet their requirements could in fact be developed. The .276 cal's raison d'etre was entirely to allow a semiautomatic rifle to be made light enough for service use (9.5 lbs or less). With it being shown by 1930 that .30 cal selfloaders this light were possible, the need for the .276 evaporated, along with the challenges it presented. Keep in mind, at this time the US had entered the Great Depression, so there was no money for anything, let alone to retool every weapon for this new caliber.