Single shot .22s.
Single shot 5.56 conversion of a Lee Enfield is easy, and they shoot very well. Bolt face is left flat.
Repeating conversion is more complex. A magazine system has to be adapted. The bolt head is altered with a recessed face, and a plunger ejector installed.
I've not set up a new hosting service since PB changed its operation. Took a few photos of the SMLE barrel being converted. Let me know your email, and I'll send them.