The cartridges up until the Mk7 had a MV ranging from 1830fps to 1930 Fps,
The MkVII mv was 2400fps. Still, the .303 served quite well in all it's variations. I doube the target knew the difference between being shot at 2400 fps and 2800 fps. Thare is no such thing as being "a little bit DEAD"
While the Metford rifling was designed for Black powder, Keep in mind that was only around for a couple of years. The Lee metford served with cordite ammo untill the hotter burning cordite washed out the shallow rifling and most of them were then rebarreled with Enfield rifling. They will handle MkVII ammo without a hiccup.
I am still amazed that ANYONE would think a two piece stock is less accurate than a one piece one. Quite a few hunting rifles have been made with two piece stocks.Thw two piece stock design made a lot good germans japs, italians,North Koreans, Chinese, and the L42A1 did for a number of Argies not to mention some arabs.
That current sniper rifles have one piece stocks is irrelevant, mainly because thats whats on the market today. The Swiss SIG 550 has a two piece stock as well as the Dragunov. I guess those must be inaccurate as well?
Again the fact that rear locking lugs are not used on modern rifles is irrelevant unless you are using high pressure ammo like 300 Win Mag, or .50 BMG ammunition Sniper rifles also use 7.62 Nato rounds and we KNOW the No4 will handle that.