Gramps and Steve P. have valid points, but it may be worth your while to weigh cases. Determine the average weight of the 1000 shells. Take 10, weigh'em, find your "average"weight. Then go maybe +/- 2-3 grns. set your scale at your highest limit and set aside anything measuring heavy. Do the same thing on the low end. 1000 shells will take you somewhere around 20-25 minutes this way. I know some people that weigh each case individually for its own weight - this will take you FOREVER. But just like they said - then you'll be weighing bullets, primers, looking at mirage boards and windage flags at the range.
I'll take the time to weigh cases, bullets, (never weighed primers, I'll have to try that!) and trickle load all my handloads simply because I enjoy the hobby - you'll get good results without the hassle. This practice "hotrods" an already good load if you've done your homework. Good Luck to Ya!!