Have owned numerous A5s. Never had one jam in 50 years. Rings have to match loads and thats where those kind of things happen. But I never coated the tube with a lot of oil. Was always told to spray it with Rem oil or equivalent and wipe off with oil rag. Never a jam. 12s 16s and 20s. Never ever...
I would say most states would be the same. As long as you went through a CO and the person leaving has his license in order. Why would it be a problem. You couldnt write your own note because you would need a extra license.
5s. By far. Im assuming pointing dogs? If not then bismuth would work betyer. But you will never need 3 inch for pheasant. Been hunting them 30 yrs, and nope never.