The D30 is a particularly common artillery piece, but it must be understood that the D30 is not some shoddy low-end product; the D30 is genuinely high-end. Although extremely common, both in terms of performance and manufacturing craftsmanship, it reflects the Soviet Union's highest standards in artillery.
Therefore, the D30 is indeed an excellent cannon, and although the artillery used by Rebrov's crew is somewhat old and the dispersion is a bit off, relatively speaking, it's still a good cannon.
The artillerymen led by Rebrov achieved the D30's maximum firing rate. Gao Yang counted clearly; each cannon fired seven shells in one minute, while the theoretical maximum firing rate of the D30 is six to eight shells per minute. So, the artillerymen belonging to Satan indeed reached the actual maximum firing rate.
