I recently got a new PSA mid-length 16" upper with 1-7 twist. I put a DD A1.5 fixed rear sight on it. I'm wondering if I should get a scope for more precise longer shoots. With the iron sights I'm shooting about 8" pattern at 100 yds and I can hit a 12" dia plate at 150 yds most of the time. I wear glasses and with the thickness of the front sight I think this is as accurate as I can get with the irons. My use for this rifle will be mostly 100-300 yard or farther plinking/target shooting. I would like to see how far it could shoot accurately. What level of accuracy can I expect from this upper and what magnification would be appropriate?