The first time I shot my first machinegun, it was owned by a friend of mine. Colt roll marked M16. He had bought two from a case of 10. One was roll marked M16 and the other was marked M16A1. What both guns were new he ran 3 mags through the M16 and put it away. He had 6,000 to 7,000 through the A1 and sold it to another friend. I told him that I wanted to buy it. We went shooting again and he pulled out the M16. It still had the factory grease on the fire control. We put around 1,000 rounds through the lower. We both had uppers we could use. About a month later he told me he wanted to sell the M16. I bought it for about half the current market value. If I ever have to go into harm's way, I would want to do so with a Colt M16. I ended up selling it after I transferred a DIAS. I prefer the modularity of the MGI lower and being able switch the DIAS into different lowers. I sold the Colt gun and a LL to buy a Fleming HK sear married to a converted 94. I am glad I bought when I did. I have almost $10,000 less money in the DIAS and the HK sear than the current market value of either.
I had to sell most all of my Title I guns to buy the Colt. If I had it to do over again, I would sell them even quicker to buy a full auto. They are so much fun. I find it funny when a collector tells me he can't afford full auto, yet he's got over 20 handguns and 15 rifles in the safe. YMMV.
Scott