I would add, to Steve's excellent info presented above, the following:
- If you are taper-crimping and seating in one step, it is possible/probable that you are getting a tiny "ridge" of bullet material just in front of the case mouth. This is a result of the bullet still being pressed slightly deeper into the case during a single-step taper-crimping process. For this reason, many/most taper-crimp dies are standalone dies; it is recommended that you seat the bullet at one station, and taper crimp with a separate die at the next station. A similar ridge of bullet material or bullet lube can also be caused by insufficient case mouth flaring (case scrapes the bullet during seating, rolling-up some lead/jacket/lube at the front edge of the case mouth), or inserting the bullet slightly crooked into the case mouth prior to seating. In either of the above situations, the round will headspace off the ridge of material in front of the case mouth, instead of the case mouth itself, giving you a false reading when you measure the depth of the round in the chamber at the barrel hood. Unless the ridge is large, rounds with minor versions of this defect will often feed/chamber/lock/fire normally.
- While I am not familiar with the exact bullet you are using, with some short SWC bullets, there is a condition similar to the one above that can be caused by a full-diameter portion of the bullet extending forward from the case mouth, and actually touching the rifling when the round is chambered (which again, will give you a false depth reading at the barrel hood). Because of the short nose and overall length of these bullets, they will often feed out of the magazine just fine, even if they are seated "long" in relation to the rifling. After you drop a test round into your barrel, invert the barrel, and see if it will drop OUT again from its own weight. If it sticks, check the bullet for any telltale marks which might indicate interference with the rifling, and adjust your bullet seating depth accordingly to eliminate it, if necessary.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)