Has anyone every done research has to how much brass weight affects precision in a T/C Contender? I'm in the process of replacing some brass(30-30) for a 7-30 Waters, and have a 3-4 grain discrepancy in the lot of Remington brass I'm using. The previous brass was Winchester, and weighed +/- .3 grn. I'm already loaded for the research, just curious to see previous results and compare them to what I find.

I weight/group matched cases ONCE for my 222.
That next range trip my groups were double in size!

Now... I'm pretty sure it wasn't due to group matching, but I never tried it again. I always group match the bulets though.