When I shoot comp, they don't let us shoot 3 shot groups. It's 10 shots at a time. Even my 9.3x2mm doesn't mind:
This is just a hunting rifle without a heavy barrel contour:
Skinny barrels shoot good too. I don't buy into the nonsense about groups walking all over because the barrel heats up too much. If your rifle is glass bedded properly and it has a good barrel, it's going to shoot good 5+ shot groups. As far as loading a rifle, I load the sob up if it takes 5 like my 30-06's and 9.3x62mm I put 5 in and maybe even one in the tube. I also automatically jack another one in after firing the first. If you want to see what rifle and shooter can do, fire off some 10 shot groups:
My 375 H&H even holds 4 in the magazine, but I generally only fire 3 shot groups in that rifle:
Admittedly, I find 3 shot groups very boring...