The initial "spitzer" bullet was about 20 grains lighter and somewhat shorter.
The original MKVII bullet was 160 grain, but, as we know evolved into the 174 grain but retaining its original nomenclature.
From the Small Arms Committee meeting minutes 8th December 1909 :
Mine are not the best, but they are not too bad. I can think of lots of Enfields I'd rather have but instead of constantly striving for more, sometimes it's good to be satisfied with what one has...