How did you contact your permissions?
I do quite a bit of research using books describing civil war battles. The better researched books will sometimes have references to present day locations. using Google Earth and the county's GIS property tax map I find areas near or in the battle field that is not protected by either the Federal or State agencies.
I then look first for parks and power lines and creeks that run through the skirmish or camp areas. On those I don't seek permissions, I just hunt.
when on private property I find the owner's name in the GIS database and type, print and sign and send them a letter via the US Postal service. I have found out the post office will send a letter if you mail one. Most people think they only bring to your home bills and junk mail. But believe it or not they will deliver a letter. And that is usually a shock to the receiver of the letter to receive a real letter from a real person.
In your letter include the research you have done, and why you think their might be relics on their land. Describe your sharing agreement and mine is 50/50 on anything over $100 in value. For instance if I was to find a CSA belt buckle, and it was worth $2,000. I would give him $1,000 and keep the buckle or sell it and we split the $2,000 50/50. On small stuff like bullets, just give him some and keep some. But my goal is to get and keep a CSA belt buckle or Union belt buckle.
Some have criticized my sharing agreement, but I figure without the permission I got zero stuff and you are much more likely to get a permission if you share and are honest with the property owner. I always show them everything I find, including junk to let them know this is not easy.