That is not my understanding Sam.....Utah recognizes any pre 1899 firearm that utilizes the ammunition that it was originally designed for..........so the question would be: what do you classify as modern ammunition....?????......
I have probably ten guns that were made pre 1899 and shoot ammuntion that is just as deadly as anything produced today and is still available over the counter, but were desinged and produced prior to 1899 and these are recognized by most states as antiques and can be bought and sold direct to the buyer......i.e.: 32-40, 38-55, .32 S & W Long, .22 rimfire, 45-70 U.S., 30-40 U.S., 44-40, 38-40, 30-30, 45-90 and the very long caliber list goes on and on, including all your shotgun bore sizes.....
There are Utah Gun Shops around here that sell pre 1899 guns without the NICS ATF requirement and also sell antiques over the internet without the FFL requirement. Picture I.D. is all that is required.
Some Northeastern states and maybe California that have their own state laws which clearly define an FFL as required FOR ANY GUN....overriding the Federal ATF Laws that are currently in place....
This topic comes up frequently as people misinterpret the ATF Regulations and FFL requirements......
As initially posted, I would say Cabela's folks are making their own rules or the floor people misinterpret the corporate rules (which is common in large stores, i.e. dummy 101).......I wouldn't do business with stores who don't understand the ATF Federal Laws and structure their business practices by these existing laws......