If it is a legal machine gun thats a great price. Have you done all the ATF paperwork to own a machine gun? What about the state paperwork?
full auto,,are you sure? didnt think they made auto ar 15' or m4's anymore,,if its from the military it would be maybe 3 round burst i would think,,but i could be wrong,,...heck i got a freind who is a security gaurd at a nuclear reactor,,and he carries a m4 from the goverment,,its semi auto,,full rock and rolls were deemed inaccurate and waste of ammo
for a colt,,ummmm not too bad,,i would keep your eyes open!! because there is no such thing as preband anymore,, so all the guns that were worth a bunch are not as much anymore,,because preban is out the window right now,even ak's have dropped down to 100 bucks a gun for china models in some places,,and m14 assalt rugers have dropped to about 600bucks,,lol fully decked out,, before the preband ended they were 1,400 bucks
but it is a colt,,i would look on colt prices,,because colt did stop selling to the public,,so it mite be worth what he wants,,i would research it on guns of america online