Well....
Now I am not trying to be contrary, but as a competitive shooter who had an eleven year obsession with tuning and shooting No4 and No 1 MK III rifles, I very much doubt any of the .303 rifles would shoot MOA, at the shorts or the longs. By that I mean 10 shot groups fired from a position or a rest with target sights from a skilled shooter who knows his stuff. That is with good MK VII cordite loads or with VIIZ equivalent in any bullet from 150 to 175 grain. Regardless of velocity tuning range from 2150 to 2450 fps.
Now I am only a Yank, but I would say an No 4 that can put 10 shots in to less than 5.5 inches at 300 yards is shooting quite well indeed. Any No 1 MK III that is doing less that 7.0 inches for ten shots at the same range is, once again, shooting very well (sling or supported, Parker sights, good eye sight, no shots called out of group).
On equivalent US weapons, using 168 grain to 175 grain .308 bullets, I would say a well tuned
M14
is capable of 4.5 inch groups at the range , again from a skilled shooter prone sling supported or a rest, an M16 NM variant with float tube an associated gizmos being more like 3.5 inches at that range. I have reasons to believe the latter figure is limited by eyesight.
Further, it has been my observation that with either the No4 or the No 1, the groups you see at the shorts are even worse. so a No 4 that shoots better than 2 MOA @ 100 yards would win any match it was entered in against other No 4 rifles, and a No1 MK III that would shoot a 10 shot groups of under 3 MOA at that distance would pretty much beat all other No 1 comers, if using full power ammunition. If the velocity of the loads for the No1 Mk III is dropped to between 2150 and 2250, the troublesome vertical wild shots seem to disappear with powders in the region of IMR 4064 speeds. In those cases a No1 MK III that can produce groups of 2.5 MOA at that range will beat all other No21 rifles on the line.
I suspect the No3 rifle would do better, I simply do not have enough experience with these rifles to make a definitive statement.
I am curious if folks who have shot the rifles from position and in matches would say they will do better than that on a regular basis.