Have you tried chambering an empty case?
Or tried a factory round?
Are your reloads really "reloads" or just new rounds you loaded?
When I just started reloading a few hundred years ago,,I was loading 357 for S&W model 28,,Everything worked fine,,Then I got a Colt and my "reloads" that worked fine in the S&W would not fully seat in the colt chambers..About 1/8" from fully chambering in the colt..My problem was that I wasn't fully resizing my brass after firing them in the S&W. And while they still chambered fine in the S&W the colt chambers were tighter ..So if you are firing your rounds in a gun with a larger chamber than your new gun,, and you are not fully resizing them then this might be your problem..Easy fix= adjust your sizing die...