Are you saying that the case head is riping off or just the rim ?
If it is just the rim ,then your problem is either not enough lube ( I use Dillon spray)or a shell holder problem (replace the shell holder).

If it the whole case head then ,if you are lubeing the case enough ( I use Dillon spray) you are getting case head seperation caused by a chamber problem or a die problem (rare ,but it happens).

How many times have the cases been fired in that rifle and FL sized?
How many times has the cases been trimed ?
I junk brass when it needs trimed the fourth time .
If the cases have been trimed more than 1 time cut a case open and see and feel if the case wall is thining just over the case head.
If thining is found then erplace the brass and find out why it is happening.
How much do the cases grow each time FL sized ?
Look at a fired unsized case and compare it to a NEW case or loaded rnd .
Is the shoulder on the fired case lots farther out than the new 1 ?
Is the shoulder diamitor lots bigger?

If the cases look ok ,it time to look at the dies.
Are they new ?
Have you used them before with no problems ?
Do the FL sized cases look like new loaded rnds ?
If the shoulder is pushed back ( in some guns the extracter will hold the rim enough to let the cart. fire ) ?
If this is the case send the dies to Horndy and demand a new set.
I have several sets of Hornady dies and love them.