Here's something that's new to me, American Engineer Russel J. Turner developed a semi-automatic version of the S.M.L.E. as a new infantry rifle which was trialed and rejected by the U.S. in 1941. Apparently some time later it was tested by Canada as a possible replacement for the No.4 rifle but was rejected and Canada eventually opted for the FN FAL. More can be read at the Historical Arms webpage here: https://www.historicalfirearms.info/...ic-lee-enfield
There have been a number of variations of an automatic Lee Enfield developed - some better than others,
One example ;
The M1915 Howell Automatic Rifle is a conversion of a standard No1 MkIII Lee Enfield Rifle into a semiautomatic, through the addition of a gas piston onto the right side of the barrel. Despite its very steampunk appearance, the Howell is actually a quite simple conversion mechanically. The rifle action had not been modified at all, and a curved plate on the end of the gas piston is used to cycle the bolt up, back, forward, and down just as it would be done manually.
The additional metal elements added to the gun are there to prevent the shooter from inadvertently getting their hand or face in the path of the bolt. The crude tubular pistol grip is necessary because the shooter’s hand on the wrist of the stock would normally be in the path of the bolt’s travel. Note that the Parker-Hale bipod on this example is a non-military addition from its time in private ownership.
In addition to these elements, the Howell has been fitted with a 20-round extended magazine to better exploit its rate of fire. However, the Howell was made as a semiautomatic rifle only, and not fully automatic. It was offered to the British military circa 1915, but never put into service. Instead, the British would significantly increase production and deployment of Lewis light machine guns. Howell would offer his conversion in basically the same form to the military again at the onset of World War 2, but was again turned down.
Shooting the Howell was remarkably successful - I had expected it to be very malfunction-prone, but in fact it ran almost completely without fault. In retrospect, I would attribute this to the simplicity of its conversion, which made no changes to the feeding and extraction/ejection elements of the SMLE. The gun was a bit awkward to hold, and the offset sights left one with really no cheek weld at all, but recoil was gentle thanks to the gas systems function and added weight.
Mine are not the best, but they are not too bad. I can think of lots of Enfields I'd rather have but instead of constantly striving for more, sometimes it's good to be satisfied with what one has...
Not quite a sow's ear out of a silk purse, but headed in that general direction.
As Ian and others have pointed out, a straight-pull action is the only sensible place to start for a semi-auto conversion.
“There are invisible rulers who control the destinies of millions. It is not generally realized to what extent the words and actions of our most influential public men are dictated by shrewd persons operating behind the scenes.”
Came across a Scmidt-Rubin M1889 re-barelled with one from a Standard Arms Model G (.30 Remington). They left the gas system on with a lug, like they were trying to make an auto loader. It's a super Bubba