I live in MA and have family in OH, and I drive out a few times every year to visit. I take firearms every time to shoot on my brother's farm - long guns, handguns, and ammo, always in separate locked containers. Generally I set the cruise control at 74 and take I-90 to I-87 to I-88 to I-86 and back to 90 to Northern Ohio - going South to PA first is hours out of the way.
This May I was stopped for speeding in Western NY, on my way back to MA (didn't have the cruise control set). Radar got me at 79 in a 65, and the state trooper wrote me a ticket for 74 because, he said, I pulled over immediately and safely, was polite and courteous the entire time, had license and registration and no other violations in NY. He never asked to search the car, and I took the ticket and drove on. It cost $168 to reminded me not to speed, and when I drive out in November I'm taking my M1, a 1911, my 39A, and hopefully a 1917 revolver I buy between now and then.
So more or less a happy ending in this case, although it could have been better and it could have been worse. The best advice is probably pack legally and drive safely.