No , Md does not have a min length for SBR generally , only for Copycats. You may have your manually operated / break open , or other form of single shot in any OAL you wish.
What would be the shortest barrel length for something like an old Ithaca 37? I assume one would form 1 the build. Would engraving be needed?
Does an SBS require a 5320 to transport out of state?
Unless you c. Want to get into complex modifications , just beyond the magazine tube.
Yes , to convert from your existing shotgun , a Form 1 . Yes , engraaving just like any other NFA.
An actual SBS requires a Form 20 , an AaOW ( AOW , keyboaard isses ) does not. Awaiting the followup thread on the fine points of what can be a Form 1 AOW vs Form S ( Form 4 ) AOW .
A form 1 or 4 AOW needs to be built from a virgin receiver or from a pistol. I'm the case of a shotgun, there is no pistol, but an AOW can be built from a factory pistol grip shotgun.
While the transfer rates are different between a SBS and AOW; $200 and $5 respectively; the making tax on both for a form 1 is still $200.
Yes. AOW'S are exempt from the 5320.20 requirement for interstate travel. 5320.20's are not that big a deal. I will literally fill out 20-30 for different locations and different firearms and send them all in at once. I do a lot of stuff in PA, and travel to several locations. I usually send them all in in September for the next year. I put Jan1-Dec 31 as the travel dates, and under reason I put Multiple frequent range trips and public/private exhibition. Never had an issue and except for other oddball trips, I am good to go for the next year.
As has been stated, there is no minimum OAL requirement for SBS's. I will tell you from experience that the shorter you go, the less effective they are at range. My 8" Saiga has a hard time clearing a clay target at 20' with birdshot, but prints a nice torso sized pattern out to 20 or so yards with buckshot and is scary accurate with slugs. I have a few projects in the fire right now, and they all will be threaded for chokes.
They are also obnoxiously loud and the concussion from them is ridiculous. Like louder and more concussion than a Barrett.
If I can be of any more help, hit me up. If you want to try before you buy so to speak, we can arrange that. SBS'S are not for everyone.