I have about 1500 rounds of heavy ball on hand, plus another 300 light ball. I haven't had any problems with the heavy ball so far (300 fired), but the tin of light ball I shot had neck splits on about 10% of cases after firing. I never noticed any cracks or loose bullets in either batch, so it may be a brass issue.
I initially bought two tins of each bullet weight and spent a week test firing with different guns, ranges, etc. After discovering the neck split issue on my light ball, I decided to stock up on heavy ball.
Accuracy-wise, I have no complaints about either bullet weight in my Mosins. I have run both types through an M44, 91/30, and M39 with zero extraction problems. Accuracy was better than Polish steel case ('84 production) and similar to Czech silvertip light ball ('86 production).
From my 1942 M39 (D barrel, VKT), I average about 3 MOA at 100 yds.
From my 1948 M44 (Izhevsk, pristine bore), I average 2-3 MOA offhand at 50 yards.
From my 1937 91/30 (Izhevsk, dark bore), I average 5-6 MOA at 100 yards.
Your mileage may vary.
PS: My heavy ball is stamped '55 production, and my light ball is stamped '51. FYI