The SLC was investigated by Naval Ordnance Inspection staff at Simonstown in West Africa. The weapon was forwarded to the Ordnance Board in London for testing. Upon testing, the bolt would not feed the top round from the magazine, and the weapon had to be loaded by hand. Recoil was higher than expected and threw off the aim to the left. It was concluded that it was not worth developing the weapon any further, and so no improvements to the design were ever made.
The SLC was adapted from a Lee-Enfield No.1 Mk.III rifle, using the same barrel (albeit shortened) and body. The feed system was overhauled and rechambered for 7.63mm Mauser. In place of the Lee-Enfield's bolt was a heavy breech block that was blow-back operated. The firing pin was held up as the bolt went forward. The trigger mechanism was much the same as the Lee-Enfield. The magazine held 12 rounds.
The weapon was never intended for automatic fire. It seems that Francis' intent was to create a small-calibre, semi-automatic carbine rather than a submachine gun, but it is sometimes referred to as the latter. All in all, the weapon weighed about 8 pounds, one and a half ounces. It measured at about 32 inches long and had a 12 3/4 inch barrel which weighed 1 pound 7 ounces.