It took me a long time to realize the value of an AR15. I hated the idea of an UGLY gun. When the first I ordered came in I was appalled, it looked like a child's toy. I leaned it on the wall doing the paper work, it made the sound of a spring ringing. I thought " what a piece of trash ", a plastic gun full of springs. I figured I would sell the thing since many others wanted them.
I decided to take it to the range before dumping the thing on someone else. It shot very straight, just the sound of the recoil buffer spring was a bit UN-nerving. I had the idea of using it for a groundhog rifle at local farms. Geeze, that rifle showed it was very handy. No wood to mark or scratch, metal surfaces that do not rust. Just chuck the thing in the truck.
With only the standard ( some what improved ) peep sights I found is easy to put a head shot on a running Groundhog over 100 yards out. Did that at least once a summer, I became very confident in making that shot. Much easier then a scoped rifle to do. With ONLY the standard though improved peep sights my best shot was a measured 483 yard head shot on a small Groundhog pup.
SO all in all yes, for a varmint rifle, I very much like my Colt Match HBar with the 1:7 twist barrel. It proved itself and has become my favorite smallbore rifle. I have always wished good Ol' Eugene Stoner got the cash due him for such a spectacular design.
ADDED : OH, do be aware of the drawback to using a standard AR15 I learned. Firearm Safety RULES : Identify your target. With only the peep sights, you have to carry a pair of binoculars along. I learned my lesson the evening I dusted a barn cat. I had been watching a "Groundhog" out in the bean field about 150 - 200 yards out. It would stand up, then duck and move only to reappear on it's hind legs again. Ooops, I still feel terrible about that. I went and fessed up to the farmer what I had done. I fully expected that cat to suddenly be a very rare and valuable cat I was responsible to compensate him for. Luckily, he had a sense of humor. He simply said there are at least 50 other cats around here, so it was OK. DOES NOT make it right, that WAS a stupid accident (stupid accidents with a firearm are not truth. It WAS carelessness, and I know better) that is why I feel terrible about that evening, and have N O excuse. SO remember .. always, ALWAYS identify your target.