My understanding is that the minimal barrel length for a shotgun is 18". Also, I believe that measurement is taken from the breech face to the muzzle. I've read that by closing the action and inserting a dowel rod in the barrel is the best way to get a measurement.
In addition to the min. barrel length I also understand that the gun must be a min of 26" in length from end to end.
Do any of you guys know this info to be accurate or factual?
We had our Riot Guns ( 870's) with barrel length of 20 in to comply with Fed Reg's and they would hold 7 rounds, either 00 Buck or slugs, we used..Always carried mine in the trunk of patrol car loaded in soft case, when I made Captain I had to turn it in for re-issue......