I have barrel "rules"...the smaller the hole, the longer the barrel. And the bigger the hole, the shorter the barrel.
Just so long as the smaller hole is not on a barrel longer than 26"s and the big hole is not on a barrel shorter than 21"...and assuming it isn't a handgun.
Or a 270/280,30-06,7/08 etc and then it can't be longer than 22".Unless it's a .22 or 243 and then it can be 22-24".
Or a 338 or 375 can be 22"-24".
And a 416-458 can be 25" but not much shorter,while a 7mm or 300 mag can be 24-26".
See what I mean?