Learning to inspect your brass isn't difficult and doesn't require much in terms of homework or instruments.
I advise anyone who takes on bottleneck rifle loading to learn how to inspect their brass and buy the Go-Gage, tools and instruments to do this, but I can also spend your money fast if you listen very long....
Learning to inspect your chamber and dies takes a little more effort, more time and more money.
If you wan to learn to debug this in general, the forum can give you some homework and a shopping list that will take some time and a credit card.
If you want to have your chamber and die inspected without tooling up or doing that homework, you can enlist a qualified gunsmith.
(It would be fair to ask whoever chambered that barrel for help as well.)
If you just want to cut to the chase, it is low risk to just get the Small Base die and have it over with.
https://www.rcbs.com/dies-and-shell...base-taper-crimp-die-set---ar-series/780.html
The last option, is to commission your own custom die. That takes even more time and more money.
You could also just collect and sell your once-fired brass and keep buying factory or use virgin brass to tailor your own loads.
It is all up to you how much time and effort you want to invest.
The middle ground is what I advise. At least learn to inspect your ammo, and be prepared to get a small base die when you take on autoloaders.
YMMV