[elcid1970]

I had read that what made the SMLE rifle so fast-firing was that the bolt rotates only seventy degrees, and the cock-on-closing action actually speeds up the reload cycle.

It was said that in 1914, when the British infantry consisted of seasoned veterans, their rate of fire was so fast that the Germans thought they were equipped with self-loading rifles, and called this “contemptible” and unfair.

So the “Old Contemptibles” they became, wielders of the dealy Enfield. But the trench warfare that followed decimated their ranks, and the raw recruits who took their place could not replicate that murderous rate of fire.

[AnAmericanMother]

It's the rear locking lugs. Because of that, the bolt only has to move the length of the cartridge. And the angle of the bolt handle means that you can "slap" it home, once you get the knack.

Of course the cock-on-lock feature means it's that much faster!