“What would be a good variant for someone on a tight budget?
Caliber, etc?”
One way to go would be to get a stripped lower, and then slowly get the various parts to build it up. The lower is the part regulated under gun transfer laws. The rest you can get either over the counter, or directly mailed to your house. By doing it this way you can get high-quality components over time, rather than settling for a “budget” rifle. Plus, you’ll learn ton about ARs. One very important area where there are a lot of options is the type/make of trigger. The basic military trigger is usually pretty heavy and gritty.
One very cool thing about AR-15 type rifles is the lower can accept any AR upper (barrel, rail, and handguard), and they are easily swapped. Uppers are available in a variety of chamberings and calibers. They aren’t considered a “gun” so there’s no red tape involved in getting one or more.
Re: uppers, lowers, easily swapped...
“They aren’t considered a ‘gun’ so there’s no red tape in getting one or more.”
H.R. 4269 Assault Weapons Ban of 2015 seeks to outlaw possession, sale, manufacture, and import of PARTS, too, as well as hundreds of types of guns. This is an attempt to criminalize build-it yourself hobbyists.
The bill is moving through committees and is in the Homeland Security committee now. Read the bill here.
https://www.congress.gov/bill/114th-congress/house-bill/4269/text