The M1 came into service for WWII. I see the biggest drawback with the M1 was it's odd loading method and inability to top-off and it's "ping" when the gun fires it's last shot. All of these seem to be a significant drawback to the rifle.
Why didn't the design use either stripper clips with the ability to top off or, even better, a detachable magazine? That would have turned a very good rifle into an excellent rifle.
While I would have given the Army some good advice about adopting a detatchable box magazine for the M1, there are reasons for the en bloc clip.
The quest for a semi-automatic rifle came down to a contest between two Ordnance designers, John Garand and John Pedersen. Pedersen was the senior man, and Garand was a transfer from the Bureau of Standards. In the normal rule of bureaucratic organizations, Pedersen would have won -- but his rifle (which used toggle lock like the Luger) could not adapt to the .30-06. So when MacArthur decided to abandon the .276 Pedersen cartridge and stick with the .30-06, Garand won. But Pedersen had to have a consolation prize -- the en bloc clip was his idea, not Garand's.
Now, to be fair, at the dawn of the smokeless powder era there were several theories of ammunition management for riflemen. The British liked a high capacity detatchable magazine (the early Lees were issued with two spare magazines.) The Americans were taken with the Krag Jorgensen outrigger magazine, which allowed topping off the magazine with the bolt locked on a live round. The Germans went with the Mauser stripper clip.
By an accident of history, both the Americans and the British went up against Mauser-armed enemies at the turn of the century -- the Spanish and Boers, respectively. The superiority of the Mauser stripper clip became painfully obvious. The Americans adopted what is basically a Mauser (the '03 Springfield) and the British greatly modified their Lee-Enfield to take stripper clips.
At that point, the issue was considered settled -- clip loading for rifles was the way to go. And, in point of fact, the en bloc clip is actually considerably faster than the stripper clip.
And the "ping" issue is a legend -- lie down outside grenade range, and let me shoot over your head. When you hear the ping, get up and charge me. I'll bet any amount you like you'll never make it to your feet.
And if I don't get you, someone else in my squad or platoon will.
The en block clip has three disadvantages -- it complicates manufacture, you can't mount a scope over the bore, and you cannot top off the magazine,
Watch your thumb.
:banghead: 
