My understanding is the new Oly Plinker's are forged upper and lower, so if you just bought it, unless it was used or old inventory, it should be forged. see
HERE to find out how you can tell whether it is cast or forged.
Many here will knock Oly, and they may have had bad experiences with them. However you should take what you read here or anywhere else with a grain of salt and place more weight on your own experience with the rifle. I have an Oly that has been 100% reliable, with no problems at all. The only gripe I had was the non-chrome lined 4140 steel barrel, so I replaced the original barrel with a chrome-lined 4150 steel barrel. The original was not corrosion resistant enough for me. Other than that, I had no problems. Many range reports I have seen on AR15.com about Plinker owners have been favorable. Go out and shoot it and have some fun, sounds like a keeper to me. I have 6000 rounds through my Oly, still runs like a champ.