I was unaware anyone ever made light, round nose bullets in .310" or .311".
Regarding Remington brass with small primer pockets... I seldom shoot 7.62x39 anymore, but still have Remington brass along with some by Winchester with the large primer pockets. Several years ago, I did a comparison of the two using a Ruger bolt-action. Loads and bullets were identical; primers were CCI-200 and CCI-400.
I didn't expect the results I got. Chronograph readings were close enough to be called virtually the same, just like the 100 yard group sizes and points of impact.