Even if you are a new shooter, you did the right thing buying 400 cases. I like to keep things practical so here is what I would do.
Before firing a shot, weigh all your brass and just load them into 100 round boxes from lightest to heaviest.
Take the lightest and heaviest few cases of the 400 and mark their bases with permanent markers and use these for setting up trimers, deburrers and if necessary neck turners after fire forming. These cases can always be used for fouling shots later on so keep them marked in their respective boxes. (with bases still marked).
Dont trim until first fire form then use some marked reject cases for setting up your trimmer and if need be deburrer. You might find a few cases which are a few thou shorter than the rest, dont bother trying to trim the rest to this extra short length. Just mark their bases and use these for foulers or for testing maximum pressures during load development.
You will likely have a few cases which dont quite get touched by the trimmer, maybe a thou or two short and a few which have only just been touched in a few spots by the trimmer, this is no problem, just put these in with the good group instead of trying to trim all cases more than necessary.
After fire forming, trimming, deburring , primer pocket cleaning etc, weigh the cases a final time and resort them back into their final 100 round boxes, ensuring any outlier cases have their bases marked with a permanent marker to ensure these cases are only used for foulers and/or initial sighters.
Before firing a shot, weigh all your brass and just load them into 100 round boxes from lightest to heaviest.
Take the lightest and heaviest few cases of the 400 and mark their bases with permanent markers and use these for setting up trimers, deburrers and if necessary neck turners after fire forming. These cases can always be used for fouling shots later on so keep them marked in their respective boxes. (with bases still marked).
Dont trim until first fire form then use some marked reject cases for setting up your trimmer and if need be deburrer. You might find a few cases which are a few thou shorter than the rest, dont bother trying to trim the rest to this extra short length. Just mark their bases and use these for foulers or for testing maximum pressures during load development.
You will likely have a few cases which dont quite get touched by the trimmer, maybe a thou or two short and a few which have only just been touched in a few spots by the trimmer, this is no problem, just put these in with the good group instead of trying to trim all cases more than necessary.
After fire forming, trimming, deburring , primer pocket cleaning etc, weigh the cases a final time and resort them back into their final 100 round boxes, ensuring any outlier cases have their bases marked with a permanent marker to ensure these cases are only used for foulers and/or initial sighters.