Hi read6737,
It is rather easy for your gunsmith to complete this job. I have done 2 now. One on a No1Mk3 and one a No4Mk1. I sleeved the barrels on both of them as crook Enfield barrels aren't hard to find! The only problem I have is getting barrel liners in Australiawhich is something you may have a drama with being in France
also. If anyone in the US can send me liners from Brownells, please let me know! Our brothers in Canada
sorted me out with all the parts needed for the No4. I found a No2Mk4 bolt here in Oz.
Mr Laidleris correct with being able to set the headspace to the bolt when you reline. When the chamber is drilled out and is plugged, the plug is made longer and then machined down to fit the bolt just closes. Then the chamber and rim recess is cut. You get a VERY tight headspace setup when doing it this way.
Just remember if it doesn't shoot well straight away to make sure you play all the contact points a little. The No1Mk3 conversion shot terribly until I played with the inner barrel bad screw tension a little bit. All good now!
regards
Anthony