Not to say that tight necks might be a problem, but with factory brass, a factory chamber, I've never heard of overly thick case necks. Most all factory chambers are generally well oversize in the neck diameter as to alloy any make of case use.

However:

As Tom noted, try a bullet base into a fired case. If it will not slide in easily - there are 3 possible problems I can think of:

1/. chamber neck diameter undersized
2/. case neck thickness too much
3/. case length is excessive, crimping the case into the bullet upon chambering. You may or may not feel this.

So: You have a list of things to check - from headspace to neck thickness to over-sizing the case shoulders - ie: pushing them back- too far - (I prefer not to move them as all) - which is LOADER caused excessive headspace, to tight necks or overly long brass. All of these, individually or when they stack up can absolutely cause really excessive pressure and excessive pressure signs.