Yes be very careful.
We came across a number of 50 cal bullets from where a WWII plane crashed outside of Brownsburg Indiana. Some smaller machine gun bullets were found also in broken up cartridge belts. We thought they were pretty cool. My dad took them to Fort Harrison to be checked. There were still live after 40 years (the find took place in the early 1970's). They disposed of them. The bullets did not look bad, some patina. But overall looked like them may have just came out of a drawer. The cartridge belts where beat up. Could have been from the impact or the years taking their toll.