What is the purpose of your load. Some times we want a chosen bullet to fit and it can just be a simple reason it won't but we don't yet see why. The 204 is a fairly new round on the market. I believe it is here to stay a long time unlike many others. The rifle can be the reason you are having problems. The twist is has often been my over looked reason for poor accuracy.
Choosing the right bullet is the way to start. The shape and weight are important. Of course the use is also important. Poking consistent small hole in a target at 300 yards is not the same as dropping a ground squirrel or Yote at 400 yards. The bullet has a job and it's up to you to choose it. Those pills can be mighty expensive so do your home work on them first. After choosing a few powders. You will have what I conceder a lot of fun coming with that cartridge. After you master that round you will be ready for another challenge. Before you know it you will see how it works.
When you think you have it try a few different primers to find the one you like best.
This is a great sight to get you going. Continue to work with us. I am anticipating you sharing your progress. I wish you well.