I don't mean any disrespect to any one, but I really have to say that the DMS-1 is a piece of crap. The best that can be said for it is that it's usable. It's much larger and heavier than it has any right to be and will cause eye strain if used for extended periods. The lack of clarity and the distortion that it exhibits caused me to give mine away.
What you should get depends on the type of shooting that you will be doing. If you're just going to be shooting at soda cans and clay pigeons and such, a good 4X is all that you'll need. Since you have a budget of $300, you can get a better than decent scope, but it won't have many bells and whistles.
The Weaver V3 is a very good scope for the money, but spend more and get better. The Leupold Mark AR scopes are pretty nice for their price point, but the eye relief shifts when you dial in the magnification. This isn't too bad with the low magnification scopes though. For the money, I like the Nikon African 1-4X. I think it has better glass than the Leupold and the eye relief doesn't shift when you dial in the magnification. The do make an "AR" version but it has a funky reticle. Personally, I'd stretch the budget a bit and go over to manventureoutpost.com and check out a Sightron SII Big Sky 1.25-5X. I ran this until I got my Nightforce. The Sightron is a really nice scope. Good clear glass, very repeatable adjustments and very little distortion. The clarity was better than that of my ACOG.
If you are going to be shooting at really small stuff like golf balls and target shooting for groups, the best budget scope that I know of is the Bushnell Elite 3200 fixed 10X with mildot reticle. At $200, it can't be beat.