Voz - The .243 is a notorious cartridge case for stretching. If you load the case too many times without trimming you are going to have a case that is too long for the chamber. You will notice this when you have difficulty closing the bolt. Because the case mouth an bullet are entering the throat and you are pinching the bullet tighter in the case. This can result in excessive pressures.
You may want to consider investing in a case trimmer. The RCBS TrimPro is a good trimmer and will last you a lifetime. And besides, trimming also squares up the case mouth which will give you better accuracy.
Once the cases are trimmed to the proper length, you will need to run a chamfering tool across the inside and outside edge of the case mouth.