That is good to know. I have not flown United for quite a while due to my region not having many United flights... It is good to know they are strict in size.Depends on the airline. American appears to not penalize firearms up to 126 linear inches, while United doesn't give firearms an exception from 62" limit.
The 1720 is only 4.8" over, so you've probably just gotten lucky, just be ready to eat the charge.
I fly American and Delta with guns and never have an issue yet.
I just checked Delta's website, and it says firearms are considered sports equipment as well and have the 115 inches restriction instead.
I guess I got lucky I only flew Delta and American with firearms