Lee pistol factory crimp dies do indeed have a resizing ring to ensure chambering in case the bullet seats all caterwhompus, the rifle dies do not. The rifle factory crimp dies all use a collet style crimp and case length is much less critical than with a roll crimp.
I would first ask about your priming setup. The press-mounted primer arm or a separate unit? Setting primers properly is the second most exacting operation in handloading, after dropping powder. It's easy to crush a primer by seating it overly hard and with the impressive leverage of that press (I have been running a RC for close to forty years) you have almost no "feel" for when the primer just bottoms out in the pocket. And there is no way to set a limit to the depth as you can with a ram prime or bench unit.
Then I would ask about the process you used to set up the sizing die. There are tolerances in both die and shell holder. Sometimes when the numbers are against you and you proceed to set the die as per instructions it produces a round too short for the chamber. With a little patience and some unsized brass you can set the FL sizer up to the rifle. You might also consider a Lee Collet Neck Sizing Die to increase your brass life. The less you work the brass the longer it lasts.
Sometimes rifles are short or long chambered also, that's what headspace gages are for. Both a die set too short and a chamber a bit too long would case that issue, though the long chamber would also have caused problems with the factory ammo and it did not, so I am less inclined to suspect any problem with the rifle. So far I am leaning towards an ammunition related cause, either a primer too high or too low or a sizing die out of adjustment.