IMHO, the best mount for the SMLE or whatever it might be (incorrectly) called: there are about a dozen names for it) is the S&K Inst-Mount for the Lee-Enfield Number 1 Rifle. It is no-drill, no-tap, fits to your rifle in a few minutes, maintains itself through tension rather than compression, no loose parts, no moving parts, rock-solid and takes standard Weaver rings and you do NOT have to remove the rear sight.
Best mount for the Number 4 is the S&K Insta-Mount for the Lee-Enfield Number 4. Again, rock-solid if a little tall.
Best mount for the P-14 is also S&K, interchanges with the P-17.
ANY of these can be moved from rifle to rifle, require no drilling holes and they all WORK. They are the BEST of the mounts available, which is the reason that I recommend them.
Didn't we just have a thread on this a few days go?
Check it out. LOTS of reasons there, pitfalls and so forth. You only have to scroll down this page, should you not understand the SEARCH function.