Your reader who wrote regarding "relocating & transport of firearms and ammo" from New Hampshire to South Carolina is trapped. There's no way out of New Hampshire without going through New York, Massachusetts, or New Jersey.
I'm sure readers in those states will have more info, but I'd suggest avoiding New Jersey at all costs. Massachusetts, despite its strong restrictions, may be the least onerous of the three; New York has a state law stipulating possession of five or more handguns is prima facie evidence of felony gun trafficking, New Jersey prohibits possession of hollow point ammunition (in any caliber) outside the home or business.
He, and you, are correct in not entrusting such goods to household move transporters, regardless of their rules. My suggestion would be to "bury" the New York/New Jersey/Massachusetts contraband at the very front of the truck under an absolutely packed and completely full load of innocuous household goods, make sure anything visible in the truck and in the first couple of layers inside the door is completely generic, totally non-suspicious "everywhere legal" household goods. Anything that could attract official attention should not be in the truck and especially not visible - plants, fruit (real or artificial), "weapons" - such as axes - or anything flammable. I wouldn't put even an empty fuel container of any type in the truck.
I'd suggest planning the trip to get to Pennsylvania by the shortest and safest route, traverse the non-American states in full daylight, arrange fuel/food/bathroom/motel stops to eliminate all stops for any reason in any of the non-American states, even if that means paying higher prices for fuel. Have maps available so alternate routes, if needed, can be easily determined, and observe each and every traffic law very strictly. Make sure the truck you rent is absolutely reliable, even if that means paying more to rent from a company that has newer trucks. An additional few hundred dollars in moving expense is vastly preferable to thousands in legal fees and confiscation of your property.
Once in Pennsylvania, while there may be some two lane travel (I-81 is 4 lane from northeastern Pennsylvania to the Philadelphia area and I-84 and I-80 connect to it from the east), he can get on Route 95 near Philadelphia and it's America from there to South Carolina. - Nosmo
JWR Replies: I generally concur. The Federal law does provide some protection, but some states like New Jersey are notorious for selective enforcement of their own laws. To be safe from prosecution from state authorities, one alternative is shipping your guns (or just their frames or receivers, for some models) to your new address, via a common carrier. By law and by the policies of the major shipping companies , you do not need to hire an FFL to do this. you simply ship them "from yourself to yourself." This often done by folks who are moving to or from Alaska and others who are visiting Alaska for big game hunts, to avoid entanglement with Canada's gun laws. Of course this approach must be timed carefully and there is the risk of theft. But it might be the best bet for folks with a lot of handguns or battle rifles.