I'm new to shooting a AR-15 rifle and needing little help. I just got my new DPMS AR-15 rifle. I hand it for about two weeks now and not a single round thur it. Has a 16" barrel and 1and 9 twist. I'm plaining on playing around up to 200 yards right now. Once I get some more money looking about butting a scope on it and shooting longer range. So I'm just wondering what is the best grain weight for it and brand to shoot thur it. From the cheapest and to the highest. Just wondering wanting to buy a case and not wanting to buy something thats not going to fire will and jam up on me and thanks for you help.