yimmy, what kind of rifle do you have? the first thing to try is running some of your casings through your rifle before loading them. after resizing and trimmings them. your rifle might have a tight chamber. if the casings will chamber before loading them then you might need to seat the bullets a little deeper. check the bullets for rifling marks on the ones that wont chamber. if you see rifling marks then you will need to seat the bullets a little more. if the casings will not chamber before loading then they need trimmed down a little more also. hope this helps you out. good luck with your reloading.