I have also use 243 lapua brass. With 243 lapua you have to TRIM alot of brass. You will have a pile of brass shavings big enough to build an birds nest after you trim 100 rds. I went 22-250 lapua, becase i hade 100 rds from a build I sold, but I keep the brass. 22-250 lapua will be alittle shorter when you size it up. I want to say like 20 ths.