Red rice (Oryza sativa L.) has high functional value, but its agronomic performance requires improvement through plant breeding. This study aimed to evaluate agronomic traits, compare grain weight, and examine relationships between agronomic traits and dry grain weight in M6-generation red rice mutant lines (G16) and the reference variety Inpari-42. The experiment used a Randomized Complete Block Design comprising 10 G16 M6 mutant lines and Inpari-42, with three replications. The experimental unit was a plot, while sampled plants within each plot were treated as subsamples. Data were analyzed using ANOVA, Duncan’s multiple range test at 5%, Pearson correlation, and simple linear regression. Significant differences among genotypes were observed in plant height, total and productive tiller numbers, panicle length, total grains per panicle, and 100-grain weight, whereas filled grain number and dry grain weight per hill did not differ significantly. Line G63 (5-14-10) showed high total and productive tiller numbers and total grains per panicle, while G63 (17-7-3) had relatively long panicles and high 100-grain weight. Total grains per panicle showed a strong positive correlation with dry grain weight per hill (r = 0.722). Correlation and regression analyses were based on genotype means (n = 11), and therefore should be interpreted as exploratory. The results indicate that G63 (5-14-10) and G63 (17-7-3) have distinct agronomic characteristics, while total grains per panicle may serve as a candidate selection trait for further validation in red rice breeding across environments.