If you intend to shoot factory ammo on occassion, now would be the time to correct it. He can simply ream the chamber forward another .001-.00?" depending on where it's at now.
If you're FL sizer is already bottoming out on the ram and the HS length of your cartridge is still too long, then you may have to modify the die, or purchase a bump die such as this...
Bushing Bump Neck Sizing Die