Especially unsuitable?  Well, maybe not the best option.  I'm sure the M14 wasn't the easiest rifle to use in Vietnam but it was probably no harder than using an M1 in Burma.  It saw service with many line units in Vietnam in 1965-1966 and continued in a niche capacity with some units until the end.  If the M14 had stayed the primary service rifle for the duration of Vietnam I doubt the outcome of most tactical engagements would have been changed one way or the other.  
 
"Would the US have been almost just as well off keeping the M-1 until the M-16 was adopted?"

All things considered, probably.

"Or, put another way, if the US could have adopted it in 1943, would it have been a better weapon in WW2?"

 

All things considered, probably.

 

I like the M14; I appreciate the classic look.  It's kind of like the 1911 though; in that, if you tune it up and train hard on it some shooters are capable of great feats of arms with it.  But Joe Average will probably do better with something else.

While I am sure that there are those who will disagree, I would have to say yes, the M-14 was a better weapon than the Garand.  But there are a number of things you have to consider:

 

The M-1 was designed for the 30-06 (7.62mm x 63mm), the M-14 was designed for the 7.62 NATO (7.62mm x 51mm).  The bullets used were of the same weight, and the smaller cartridge could be loaded to achieve the same performance as the larger in part due to improvements in the propellant powder.  The 7.62 NATO is still a real rifle cartridge, not an intermediate round like used in the AK-47 and M-16.

 

The smaller cartridge is also lighter (obviously) and does not require as large a receiver (again obvious) so a similarly equipped empty M-14 is shorter and lighter than the than the M-1.

 

The big advantage of the M-14 over the M-1 is in the ammunition handling.  The M-1 uses an 8 round 'en-bloc' clip that could not be removed or 'topped-off' without cycling all remaining ammunition through the gun.  It was apparently was not uncommon for soldiers in combat to squeeze off the last 1 or 2 rounds in a clip after a fire fight was over to clear the weapon so that they could insert a fresh clip.  The M-14 uses a detachable 20 round box magazine to solve most of these problems and increase the in gun ammunition by 150%.

 

The rest of the M-14 operating mechanism is an adaptation of the M-1's.  So, the reliability of the two weapons is about equal.

The M-1 uses an 8 round 'en-bloc' clip that could not be removed or 'topped-off' without cycling all remaining ammunition through the gun.  It was apparently was not uncommon for soldiers in combat to squeeze off the last 1 or 2 rounds in a clip after a fire fight was over to clear the weapon so that they could insert a fresh clip.

All good point,

 

I would like to add that the M-14s Full Auto was not that useful and well trained soldiers probably did not need it. So to answer the Original Question, YES it was better to replace the M1 with the M14 due to the box magazine, new NATO round and smaller/lighter weight.

 

With respect to the M16 I believe in the Jungles of Vietnam the 5.56 would tumble if it hit to much fauna. The heavier NATO round would probably plow through that environment better. 

 

 

I was talking to a guy the other day who went through basic in the early 60s when they were moving from the M1 to the M14. He went through basic with the M1 but saw people adopting the M14. Some guys on the range were using it in full auto and the gun was recoiling over their heads. It was very dangerous. The plans to move onto the M16 were already in motion at that time. 

 

 

One weapon that I think should be in the discussion is the BAR. Full/Semi .30-06. Much heavier than the M14 thus it probably was more stable on Full-Auto. Both had 20 round boxes. The M14 always look to me like a merging of the BAR and M1 with the 7.62 NATO.

Quite honestly the US Army Ordanance Dept had it's collective heads up their butts when they adapted the M1 Garand as is.Yes it was better than everyone else's bolt action rifles but it boggles the mind why they didn't modify it to accept the BAR's 20 round magazine.

Think about it...semi auto 20 round detachable magazine vs 8 round en bloc type

The advantages are even better when you think that both the rifleman and squad automatic weapon person use the same magazines...

Quite honestly I like the M1 and would rather carry one in combat than any M-16/M-4 piece of crud...but a 20 round detachable magazine would be better....ala the M-14

I carried the old M16A1's and had nothing but problems with them...double feeds, jams at the slightest hints of dust, etc and I'm glad I didn't have to go to combat with one....I was impressed with their accuracy but an M14 is just as accurate and much more reliable and shoots a much more effective round.

As to the poster who said the M16 rounds deflect when hitting foliage wheras the heavier rounds plow thru...not entirely accurate....ALL rounds will deflect when hitting foliage...heavier rounds just deflect less. I use a 45-70 for hunting with 400 gr bullets....they will deflect as well.

 

Then Ispose you're counseling EVERY infantryman in the Second World War, to carry a BAR.  A 19 pound weapon, unloaded, PLUS the weight of the 20 round magazine?  The reason for the 230 round magazine was automatic weapons fire, and the reason for the weight was automatic weapons fire.  You are seriously burdening the infantryman...the BAR Team consisted of several folks, the majority of whom carried magazines for the BAR.

 

Lastly, the BAr was a poor automatic weapon...it needed a larger magazine capacity.  So it seems you are recommending that the US adopt a poor machine gun, for everyone in the front lines.

 

The M-1 was the right choice...it was a semi-automatic weapon, designed for single shots, for a person in the role of the RIFLEMAN.  What you  recommend blurs the idea of automatic rifleman and rifleman and really weighs down the troops.

Please correct me if I'm wrong but didn't the M-1 clip pop up and out when fully expended - landing with a rather loud clang on the ground?  I do recall one WWII vet telling me that he used to keep a spare empty clip - and during a close in fire fight he would shoot off several rounds and then throw the empty clip on the ground to fool nearby Japanese soldiers into thinking his M-1 was out and he had to reload. 

True that out fire powered Japanese and Germans would wait for that noise to squeeze a few rounds off.

 

 

As to the M-14 being more reliable than the M-16/M-4. Ask Horsesoldier who posts here.M-14s have been used a lot in Iraq and its supposed reliability turned out to be a myth. Sand screws it up just like a M-4 would. You have to keep both clean.

I've read that the M-1 Garand was originally supposed to use the BAR twenty round magazine, but this was rejected by the geniuses in the military bureaucracy because a magazine protruding from the weapon would supposedly disrupt the manual of arms while the weapon was being carried on parade.  I cannot think of a dumber way to design a rifle, but unfortunately things like how a rifle was carried while the troops were marching up and down the square (shout out to Monty Python) was an important detail to a lot of desk jockeys.  A detachable magazine probably would have made the Garand an even more outstanding rifle, and probably would have saved a lot of lives. 

 

The United States almost adopted the FN FAL in the 1950's, but chose the M-14 largely because the FAL was a foreign design.  In my opinion this is another dumb reason to not adopt a weapon, but in the 1950's not being made in the United States was often a disqualifying trait for weapons systems competing for adoption with the US military.  This is part of the reason why the US military got stuck with the crummy M-60 machine gun, while there were much better designs out there.  One of those designs, the FN MAG, recently replaced the M-60 in the US military and will probably continue to soldier on for another decade or two.