I'm looking to get an optic for the RPR 556. I plan to use it as a training rifle and a way to shoot long range for cheaper. 1,000 yds would be the max with most shots around 600 max. I'd like to stay around $400. I already have an Argos BTR 6-24 on another rifle. I'm not opposed to getting another one, but I want to get a better idea of some of the options out there. I'm considering the Vortex DB tactical 6-24 because it fits the price range and I've heard the glass is better. Any other options I should look at? I'd also like to buy used if possible since I can get stuff for under my budget or get higher quality glass that fits into my budget. So if you see anything around the used markets that would work for me please let me know! Thanks!