have a question..

I have an axis II 223rem HB and when reloading 55gr hornady v max I have to seat super deep because I will hit the rifling. book says 2.250 and I have to go 2.230. I began loading for my axis I 223rem regular barrel and it seems I could just seat the bullet at like 2.280-(just a guess) I made my dummy round and that throat is super long. why is that? could something have became loose?