hi there, a differen type of HT low mount and history??

[muffett.2008]

This is rather surprising to say the least. Were Lithgow actions built in peacetime not in all respect superior to anything made during WWI? That defies logic.

The early actions were very well made, basically lovingly made.........in order to show their Brit. masters that they were able to build a good firearm.
In the 1915 campaigns in the desert, the tight tolerences of these rifles was causing a few problems with sticky bolts due to ingress of sand(and later mud in the european battlefields) so the body channel was relieved slightly and the chamber modified to relieve the problems.
This became standard from late 1916, early '17, hence most of the HT's being '15 and '16 actions.

Post war rifles were finished very well, rifles selected for rifle club use post 1934(H pattern) were very tight chambered and incredibly accurate as expected with a heavy barrel and tighter tolerances.