Since you have a micrometer/caliper available to measure (good deal - all loaders should have something!), measure a couple of the rounds that don't go into the case gage. I agree that all rounds should pass a standard loaded-round gage!
What causes me problems is the BASE of the case, just above the extraction groove. Especially with "range brass" that came from who-knows-where. There are several guns commonly in use, chambered in.45 auto, that allow the base to swell when fired. A standard sizer die cannot remove that bulge. When you measure, if you get ANY diameter above 0.473 inch, except for the "rim" itself, you have a badly bulged case. Not to mention any names, but G*&^K and grease guns and other sub guns all have unsupported or very sloppy chambers that allow the base area to swell on firing.
It is hard to bulge a 45 auto case up at the mouth with just a taper crimp that tightens down to 0.472. That is just barely crimping. If you are seating and crimping in a single die, back off the die body to just seat, but not crimp at all, a few cases. If those will not chamber, then you are not causing your problem just by adding the crimp!
Most of the 45 auto 230 grain LRN are made to crimp right at the leading edge of the "driving band". Shorten your OAL until you can get the mouth to slip up over the band and crimp right where it starts the nose ogive curve. Then, look down from the top of the loaded round and see that you can still see part of the thickness of the case mouth that has not been buried into the lead of the slug. Just a little of the thickness should be crimped into the lead, most should be left free of the lead so that proper headspacing (on the mouth of the case) is not lost. You are probably trying to jam the leading edge of the lead driving band of the slug into the beginning of the throat of the barrel
Make sure you do not get any bulging of the exposed part of the slug just above the crimp when you crimp, either. That is a problem some folks have with the 200 grain SWC (cast much softer usually), not normally with the 230 gr LRN.
Most commercially cast 45 auto slugs are cast REALLY hard, like 14-16 Brinnell hardness. Sometimes it take a firmer hand on the seating step to make the crimp - sorta like seating jacketed slugs.
If all else fails, then I would get a separate crimp die to apply the taper crimp after you have seated to the desired length. I favor the Redding profile crimp die, but the Lee Factory Crimp Die is very good, and has an extra use.......It can be used to remove those nasty bulges that the sizing die cannot reach by getting the "add on" parts in the "Lee Bulge Buster." Those extra parts allow you to size the ENTIRE case (even the rim, which is OK, if not actually "factory spec"). If you do have bulges down by the base, the Bulge Buster is the only cheap way to get them out. I found I went from having 5-10 rounds per hundred not fit the loaded round gage to less than one per hundred when I started "busting the bulges" off of all my 45 auto cases.
And, finally, there are a few designs of the 230 grain lead round nose molds that make a slug which does not taper quickly through the ogive. The fat nose can hit the throat and rifling and prevent the round going in the chamber the last 1/10 of an inch. Compare the slugs you are using to those that known-successsful 45 auto shooters are using. Personally, I dislike the LRN so much that if I shoot a 230 grain bullet in the 1911, I use a 230 grain Truncated Cone bullet, which NEVER hits the rifling if seated at the correct OAL.
Good luck, GJ
PS - the "bulge" you see in the case mid-height at the base of the seated slug is normal. A 45 auto sizer die takes the brass down to a little less than 0.473 inch. Inserting the slug counts on having neck tension from that tight case help hold the slug in place. All this works right when you figure out your other problems. It is ALMOST NEVER solved right by dropping down to a .451 bullet diameter, and besides, you will have a hard time convincing a commercial caster to size small just for you. You have a different problem than the bullet diameter. If you doubt this part, measure the case right where the bullet bulge is the most visible. I'll bet you are not over 0.473 inch - the magic diameter for a well-formed loaded round.
GJ