Case weight does affect accuracy. But, In my experience, the larger cases, like 300 win mag, are affected less by small differences in weight than small varmint cartridges. I think you should be fine. You could do a little test and keep the brass separated, work up a load with the lighter brass, then after finding your load, load it in the heavier brass and see how she does. If it were me, I’d just load them, ive got plenty of guns that are .5moa that I’ve never checked the brass
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