I'm not sure if this topic has been covered already, if so my apologies. I have read that the Farquar Hill and Charleston autoloading, semi auto rifles were developed from Lee Enfield conversions during the first world war and post 1918. The reason given for there limited production and lack of implementation as a large scale service rifle was due to "So called development difficulties". I found the explanation quite vague. Was this due to costs, polictics or because the bolt action Lee Enfield was viewed sufficient for the job?
I'm not sure of the exact locking mechanism of the Farquhar-Hill but it doesn't look much like a Lee Enfield. It used an indirect gas operation with a piston which compressed a spring which in turn operated the mechanism. The gun was around for a long time, being tested in various versions (including one using a rimless cartridge) before authority was finally given to order 100,000 examples in May 1918. This was cancelled at the end of the war before any had been delivered.
I dont know much about the subject, but I do know the British preffered bolt actions because the soldiers would not shoot as much ammo off as quickly as if they had semi of full autos. They also preffered to supress the enemy with accurate fire, instead of a hail of bullits. They changed after ww2, and started to lay down an incredible hail of bullits on the enemy instead of accurate fire.
On the contrary, the British Army which entered WW1 focused on very fast aimed fire. Infantrymen were expected to get off 15 aimed shots per minute from their Lee Enfields (including reloading time) and the most skilled troops could achieve an impressive 30 rpm. When the German troops first encountered a British Army unit in 1914, they reported that they were heavily armed with machine-guns, such was the volume of fire, but in fact that unit had only rifles. This performance fell off during the war, as there was insufficient time for new troops to be trained and to practice.
Lord Forbes writes about his battallion commander firing 5 shots in 7 seconds at 100 yards with the Lee Enfield in training. (recorded in the book 'We're awfa far fra hame now')