It depends a lot on the exact model of the conversion some still have the military barrels others have new military barrels fitted and some have P-H manufactured barrels. Now for instance many years ago I had a pair of the No1 conversions one was the Supreme the other a std the only real difference on these models was the woodwork. The supreme had new sporting wood by Sile of Italy the std had sporterised military wood. I picked up a spare Supreme butt stock and fitted that.
Both or these were built upon 1916 manufactured action by BSA one had Australian the other New Zealand service marks. Both barrels were good. Using the Hornady 174 grain RNSP and H4895 the Australian issued one would place five shots into a group of under MOA with a Nikko Sterling 3x32 Special Sporting scope that had the fine cross hair reticle.
Both had to be sold to pay bills a long time back after being made redundant... actually from a firm after the SA80 contract was ended.
I now own a No4 Supreme built on a No$ Mk1/2 receiver:-
That sad butt pad has been replaced by a ribbed rubber BSA pad.
Due to the stupidity of the "expanding ammo" farce I have not been able to try the Hornady 174 grn RNSP through this one and so cannot directly compare how well it shoots. With MkV11 ball it's not bad. I do have the scope mounts for it and also had a P-H 5C sight on it for a while. The No4 barrels I find are not as well made tolerance wise as the earlier No1's.
The P-H Custom is the one I believe that had the P-H manufactured barrels fitted but I cannot locate in any of mu catalogues where it says this is the case. In one it states that "carefully" selected barrels are used in their build. I have seen one that did have a P-H barrel on it. The Knox form was longer and a more gentle taper than the std "Enfield" barrel. I am trying to recall where I saw it now.
Oh yes the custom used special scope mounts as they removed the charger bridge on them.
Also ear in mind that a cuple of other firms built Enfield conversion that look pretty much identical t the P-H ones. London Armoury and Collins Bros spring to mind. I believe Stirling also did some very similar conversions. I have seen a couple of those but in 7.62x51.