The only reference I have so far found says that it is similar to the ".22 No2". the "Lee Enfield " book shows a rather end on picture that does not really help perhaps one of the other forum members who have contributed to this thread can post some pictures of the bolthead.
I am not new to "Enfields" just fairly new to this forum, I found it by accident it was probably the best accident I ever had!!!
I aggree about the ammo, sub sonic seems to produce the best results and I have a selection that I intend to try in the new beast, I will post the results when I have them.
I am lucky to have in my collection a .22 Short Rifle MkII, a B.S.A. built "Volunteer".22 Long Rifle Mk1 ( well thats what it looks like but as there are no service markings it is the closest I can get). Two No2 MkIV* one by B.S.A. and the other by Lithgowicon. A No7 that has been rebarreled, a No 8 and an Alf J Parker No9 look alike that is built on a M47 1943 dated No 4 Mk1 action.
I intend to upload photos and details of the more interesting ones eventually but if there is anything that takes your fancy please let me know and I will try to get it done for you.