My uncle served in Korea, his rifle was a No4Mk1 303. He said the 303 served him well in the heat and cold of Korea.
During training the military higher ups took his No4 and replaced it with a Sten, he said he hated that *** and demanded his No4 back.
I noticed a scar on his left arm that ran from his wrist to his elbow, he told me it was from when they were issued a 303 they would clean the outside and shoot it until all of the cosmoline boiled out from the heat of the rifle being fired so many times, the scar was from hot cosmo running down his arm.
He was a man of few words, when I asked him what bullet he recommended for the 303, he said, the 180 grain of course.
I asked him why, he replied with a very short answer, "more thump".